Abstract
A light emitter, comprising a monolithic n-type layer (comprising at least first and second n-type regions), a monolithic p-type layer (comprising at least first and second p-type regions), at least a first isolation region and at least a first electrically conductive via that extends through at least part of the first isolation region. At least part of the first isolation region is between the first n-type region and the second n-type region, and/or least part of the first isolation region is between the first p-type region and the second p-type region.
Claims
1-20. (canceled)
21. A light emitter, comprising: at least a first monolithic n-type layer; at least a first monolithic p-type layer; at least a first isolation region; and at least a first electrically conductive via, the monolithic n-type layer comprising at least a first n-type region and a second n-type region; the monolithic p-type layer comprising at least a first p-type region and a second p-type region, the first n-type region and the first p-type region together comprising a first light emitting device, the second n-type region and the second p-type region together comprising a second light emitting device, at least a first part of the first isolation region between the first n-type region and the second n-type region; the first electrically conductive via extending through at least part of the first isolation region.
22. A light emitter as recited in claim 21, wherein the first isolation region comprises at least a first insulating material.
23. A light emitter as recited in claim 22, wherein the first insulating material comprises at least one oxide and/or at least one nitride.
24. A light emitter as recited in claim 23, wherein the first insulating material comprises at least one material selected from among SiO.sub.2 and SiN.
25. A light emitter as recited in claim 21, wherein the first isolation region comprises at least a first insulating material in a trench between the first n-type region and the second n-type region.
26. A light emitter as recited in claim 25, wherein the first electrically conductive via extends from the first n-type region to a contact that is electrically connected to a p-type region.
27. A light emitter as recited in claim 25, wherein the first electrically conductive via extends from the first n-type region to a cathode contact.
28. A light emitter as recited in claim 25, wherein: the first p-type region has a first surface that defines a first plane, and the first electrically conductive via extends from the first n-type region to a location substantially co-planar with the first plane.
29. A light emitter as recited in claim 21, wherein at least a second part of the first isolation region is between the first p-type region and the second p-type region.
30. A light emitter as recited in claim 21, wherein at least part of the first isolation region is in a first trench between the first n-type region and the second n-type region.
31. A light emitter as recited in claim 30, wherein the first trench is also between the first p-type region and the second p-type region.
32. A light emitter as recited in claim 21, wherein: the first light emitting device has a first light emitting device cathode contact and a first light emitting device anode contact, and the second light emitting device has a second light emitting device cathode contact and a second light emitting device anode contact.
33. A light emitter as recited in claim 21, wherein: each light emitting device in the light emitter has its own anode contact and its own cathode contact.
34. A light emitter as recited in claim 21, wherein: each light emitting device in the light emitter is independently electrically connected.
35. A light emitter, comprising: at least a first monolithic n-type layer; at least a first monolithic p-type layer; at least a first isolation region; and at least a first electrically conductive via, the monolithic n-type layer comprising at least a first n-type region and a second n-type region; the monolithic p-type layer comprising at least a first p-type region and a second p-type region, the first n-type region and the first p-type region together comprising a first light emitting device, the second n-type region and the second p-type region together comprising a second light emitting device, at least part of the first isolation region between the first p-type region and the second p-type region; the first electrically conductive via extending through at least part of the first isolation region.
36. A light emitter as recited in claim 35, wherein the first isolation region comprises at least a first insulating material.
37. A light emitter as recited in claim 36, wherein the first insulating material comprises at least one oxide and/or at least one nitride.
38. A light emitter as recited in claim 37, wherein the first insulating material comprises at least one material selected from among SiO.sub.2 and SiN.
39. A light emitter as recited in claim 35, wherein the first isolation region comprises at least a first insulating material in a trench between the first p-type region and the second p-type region.
40. A light emitter as recited in claim 39, wherein the first electrically conductive via extends from the first n-type region to a contact that is electrically connected to a p-type region.
41. A light emitter as recited in claim 39, wherein the first electrically conductive via extends from the first n-type region to a cathode contact.
42. A light emitter as recited in claim 39, wherein: the first p-type region has a first surface that defines a first plane, and the first electrically conductive via extends from the first n-type region to a location substantially co-planar with the first plane.
43. A light emitter as recited in claim 35, wherein at least part of the first isolation region is in a first trench between the first p-type region and the second p-type region.
44. A light emitter as recited in claim 35, wherein: the first light emitting device has a first light emitting device cathode contact and a first light emitting device anode contact, and the second light emitting device has a second light emitting device cathode contact and a second light emitting device anode contact.
45. A light emitter as recited in claim 35, wherein: each light emitting device in the light emitter has its own anode contact and its own cathode contact.
46. A light emitter as recited in claim 35, wherein: each light emitting device in the light emitter is independently electrically connected.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0364] FIG. 1 is a cross-sectional schematic of a conventional light emitting diode.
[0365] FIG. 2 is a cross-sectional schematic of a plurality of light emitting diode devices on a common substrate utilizing a first isolation technique.
[0366] FIG. 3 is a cross-sectional schematic of a plurality of light emitting diode devices on a common substrate utilizing a second isolation technique.
[0367] FIG. 4 is a cross-sectional schematic of a plurality of light emitting diode devices on a common substrate interconnected by a submount to provide a monolithic light emitter.
[0368] FIG. 5 is a schematic representation of an interconnection of individual light emitting devices within a monolithic light emitter.
[0369] FIG. 6 is top view of a plurality of mechanically connected light emitting diode devices on a common substrate.
[0370] FIG. 7 is a top view of an electrical interconnection on a submount suitable for use with the plurality of mechanically connected light emitting diode devices on the common substrate illustrated in FIG. 6.
[0371] FIG. 8 is top view of a plurality of mechanically connected light emitting diode devices on a common substrate.
[0372] FIG. 9 is a top view of an electrical interconnection on a submount suitable for use with the plurality of mechanically connected light emitting diode devices on the common substrate illustrated in FIG. 8.
[0373] FIG. 10 is a top view of an electrical interconnection on a submount that also includes additional circuitry to drive a monolithic light emitter.
[0374] FIG. 11 is a top view of a self-contained element including a monolithic light emitter, additional lighting devices and power supply circuitry on a submount.
[0375] FIG. 12 is a cross-sectional schematic of a plurality of light emitting diode devices on a common substrate with back-side contacts.
[0376] FIG. 13 is a cross-sectional schematic of a plurality of light emitting diode devices on a common substrate with back-side contacts according to alternative embodiments.
[0377] FIG. 14 is a cross-sectional schematic of a plurality of light emitting diode devices on a common substrate interconnected by a submount to provide a monolithic light emitter.
[0378] FIG. 15 is a cross-sectional schematic of two common substrates electrically interconnected by mounting one substrate on the other.
[0379] FIG. 16 is a top plan view of the two common substrates of FIG. 15 before mounting.
[0380] FIG. 17 is a circuit diagram of the interconnected substrates of FIG. 15.
[0381] FIG. 18 is a cross-sectional schematic of two common substrates electrically interconnected by mounting each on an interconnect disposed between the two substrates.
[0382] FIG. 19 is a cross-sectional schematic illustrating the interconnection of multiple substrates having vertical light emitting diode devices formed thereon by stacking the substrates on each other.
[0383] FIG. 20 is a circuit diagram of the interconnected substrates of FIG. 19.
[0384] FIG. 21 is a cross-sectional schematic illustrating the interconnection of multiple substrates having lateral light emitting diode devices formed thereon by stacking the substrates on each other.
[0385] FIG. 22 is a top plan view of a common substrate having light emitting diode devices of differing sizes formed thereon.
[0386] FIG. 23 is a top plan view of a common substrate having non-rectangular light emitting diode devices formed thereon.
[0387] FIG. 24 is a top plan view of a common substrate having light emitting diode devices of differing sizes and shapes formed thereon.
[0388] FIG. 25 is a top plan view of a common substrate having light emitting diode devices that can be selectively interconnected to avoid connected shorting light emitting diode devices together.
[0389] FIG. 26 is a flowchart illustrating operations for selectively electrically connecting light emitting diode devices that are mechanically connected on a common substrate.
[0390] FIG. 27 is a top plan view of a submount incorporating fused connections.
[0391] FIG. 28 is a schematic drawing of a lighting system according to some embodiments of the present inventive subject matter.
[0392] FIG. 29 is a schematic drawing of a lighting system according to some embodiments of the present inventive subject matter.
DETAILED DESCRIPTION OF THE INVENTION(S)
[0393] The present inventive subject matter now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the inventive subject matter are shown. However, this inventive subject matter should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive subject matter to those skilled in the art. Like numbers refer to like elements throughout. As used herein the term and/or includes any and all combinations of one or more of the associated listed items.
[0394] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the inventive subject matter. As used herein, the singular forms a, an and the are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms comprises and/or comprising, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
[0395] As noted above, the various aspects of the present inventive subject matter include various combinations of electronic components (transformers, switches, diodes, capacitors, transistors, etc.). Persons skilled in the art are familiar with and have access to a wide variety of such components, and any of such components can be used in making the devices according to the present inventive subject matter. In addition, persons skilled in the art are able to select suitable components from among the various choices based on requirements of the loads and the selection of other components in the circuitry.
[0396] A statement herein that two components in a device are electrically connected, means that there are no components electrically between the components, the insertion of which materially affect the function or functions provided by the device. For example, two components can be referred to as being electrically connected, even though they may have a small resistor between them which does not materially affect the function or functions provided by the device (indeed, a wire connecting two components can be thought of as a small resistor); likewise, two components can be referred to as being electrically connected, even though they may have an additional electrical component between them which allows the device to perform an additional function, while not materially affecting the function or functions provided by a device which is identical except for not including the additional component; similarly, two components which are directly connected to each other, or which are directly connected to opposite ends of a wire or a trace on a circuit board or another medium, are electrically connected.
[0397] Although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers, sections and/or parameters, these elements, components, regions, layers, sections and/or parameters should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present inventive subject matter.
[0398] Embodiments in accordance with the present inventive subject matter are described herein with reference to cross-sectional (and/or plan view) illustrations that are schematic illustrations of idealized embodiments of the present inventive subject matter. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the present inventive subject matter should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated or described as a rectangle will, typically, have rounded or curved features. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region of a device and are not intended to limit the scope of the present inventive subject matter.
[0399] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive subject matter belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. It will also be appreciated by those of skill in the art that references to a structure or feature that is disposed adjacent another feature may have portions that overlap or underlie the adjacent feature.
[0400] According to the present inventive subject matter, there is provided a higher voltage, lower current device, so that system benefits can be obtained. While the discussion herein frequently refers to light emitting diode devices, the present inventive subject matter is applicable to all types of light emitting devices, a variety of which are well-known to those skilled in the art. The light emitting devices can be any desired component which is capable of emitting light upon being supplied with electricity, e.g., solid state light emitting devices, including inorganic and organic light emitting devices. Examples of types of such light emitting devices include a wide variety of light emitting diodes (inorganic or organic, including polymer light emitting diodes (PLEDs)), laser diodes, thin film electroluminescent devices, light emitting polymers (LEPs), a variety of each of which are well-known in the art.
[0401] In particular embodiments of the present inventive subject matter, the light emitting devices are light emitting diode devices. In some embodiments, the light emitting diode devices are isolated from one another by one or more insulating region(s), in other embodiments, the light emitting diode devices are isolated from one another by one or more trench(es), and in still further embodiments, the light emitting diode devices are isolated by both one or more trench(es) and one or more insulating region(s). The light emitting diode devices may be lateral devices, vertical devices or some of each.
[0402] According to the present inventive subject matter, instead of using a single P/N junction, the device is made into multiple regions so that each isolated region can be series connected to obtain the desired series-parallel arrangements that provide high voltage operation and fault tolerance in the device. In this way, a large area (single component) can be used with the benefit of placing (or packaging) fewer chips while still obtaining the best overall system performance.
[0403] Some embodiments of the inventive subject matter use flip-chip technology to mount a large area multi-light emitting device to a submount having electrical interconnection formed in and/or on the submount. As used herein, the term light emitting device refers to an individual light emitting structure (e.g., a light emitting diode structure) that may be separately electrically connected to other light emitting diode structures in a series and/or parallel configuration. The multiple light emitting devices remain mechanically connected to each other, for example, by a common substrate, and are not singulated but provide a monolithic structure of multiple independently electrically connectable light emitting device structures. Because in these embodiments, the individual light emitting devices will be electrically interconnected by flip-chip mounting to a submount, preferably, each light emitting device includes both anode and cathode contacts on the same side of the monolithic structure.
[0404] In accordance with the present inventive subject matter, there is provided a light emitter which comprises a plurality of light emitting devices which are mechanically interconnected to one another (e.g., on a common substrate on which the devices were formed).
[0405] The interconnection electrically connects the mechanically connected light emitting devices to provide a high voltage monolithic large area structure, in which the light emitting devices are electrically interconnected to provide an array of at least two serially connected subsets of light emitting devices, each subset comprising at least three light emitting devices electrically connected in parallel.
[0406] FIGS. 2 and 3 are schematic cross-sections of pluralities of light emitting devices, in this embodiment, light emitting diodes. The individual light emitting diode devices may have any desired light emitting diode device configuration, including the configuration described above with reference to FIG. 1. As seen in FIGS. 2 and 3, the individual light emitting devices 16 remain on the substrate 100 to provide a plurality of separate light emitting diode devices 16 that are physically connected by the common substrate 100. Because the light emitting diode devices 16 are to be flip-chip mounted such that light is extracted through the substrate 100, the substrate 100 should be substantially transparent. For example, the substrate 100 may be sapphire, spinel, semi-insulating or insulating SiC, semi-insulating or insulating Si, semi-insulating or insulating GaN, semi-insulating or insulating ZnO, or semi-insulating or insulating AlN. The substrate material will, typically, be selected based on light emitting diode device material selection.
[0407] FIGS. 2 and 3 illustrate two techniques for defining the individual light emitting diode devices 16. In particular, FIG. 2 illustrates trench isolation and FIG. 3 illustrates ion implantation to make the implanted regions semi-insulating or insulating. Referring to FIG. 2, the trench isolation may be provided by etching, laser scribing, sawing or otherwise forming a trench 114 that extends through the active layers of the p-contact layer 108, the quantum wells 106 and the n-contact layer 104 and to/through the buffer layer 102 to the substrate 100 to isolate individual devices. In some embodiments, the trench extends into the substrate 100 as illustrated in FIG. 2. In other embodiments with an insulating buffer layer, the trench may only extend to the buffer layer 102. Furthermore, the trench may also be filled with an insulator, such as an oxide or nitride (e.g. SiO.sub.2 or SiN).
[0408] FIG. 3 illustrates an alternative technique for isolating individual devices. In FIG. 3, ion implanted regions 116 define the peripheries of the individual devices 16. The ion implanted regions are semi-insulating or insulating. As with the trench 114, the ion implanted regions 116 extend through the active layers of the device and, in some embodiments, into the substrate 100.
[0409] The die which includes a plurality of isolated light emitting devices 16, is separated from a wafer to provide a monolithic structure that includes a plurality of light emitting devices 16. This separation process may, for example, be carried out by sawing, scoring and breaking or other techniques known to those of skill in the art for separating die within a wafer.
[0410] The substrate 100 may also be thinned, laser patterned, etched or subjected to chemical mechanical polishing (CMP), or in some embodiments completely removed. For example, as illustrated in FIG. 4, light extraction features 120 may also be provided on the substrate 100 to improve extraction of light through the substrate 100. In particular embodiments, the light extraction features 120 approximate a moth eye structure. In other embodiments, other light extraction features 120 may also be provided. Various light extraction features are known to those of skill in the art. Techniques for patterning the substrate 100 for light extraction are also known to those of skill in the art.
[0411] In addition, the light emitting devices 16 may also include one or more phosphors or other luminous materials on the substrate 100. Such luminous material materials may be provided on the substrate 100. For example, a YAG phosphor may be provided in a glob or conformal application on the substrate 100.
[0412] FIG. 4 illustrates embodiments of the present inventive subject matter for electrically interconnecting the mechanically connected light emitting devices 16 on the common substrate 100. As seen in FIG. 4, an interconnection submount assembly 200 includes a submount substrate 202 with optional mirror and insulating layers 204 and 206. Electrically conductive contacts 210 and 212 and interconnects are provided on the insulator layer 206 to electrically connect the light emitting devices 16 when mounted to the submount assembly 200. The interconnects connect the light emitting devices 16 in the two dimensional array discussed above and schematically illustrated in FIG. 5.
[0413] The light emitting diode devices 16 may be mounted utilizing, for example, solder bump technology, gold bump technology, conductive epoxies, eutectic bonding or other techniques known to those of skill in the art.
[0414] The submount substrate 202 may be any substrate material that provides suitable structural rigidity including, for example, semi-insulating Si, semi-insulating SiC, semi-insulating diamond, CuMo, Ge, metal alloy, metal oxides, Cu, Al, steel with insulator and/or PCB materials, a thermally conductive plastic with or without filled, BN, a transparent ceramic (very small grain size ceramic) or other insulating materials, such as BeO. Preferably, the submount substrate has a high thermal conductivity so as to aid in dissipating heat from the light emitting diode devices. In some embodiments, the submount assembly 200 itself could be a large area light emitting diode device.
[0415] The insulator layer 206 may, for example, be an insulating metal oxide (e.g., AlOx), an organic such as fiberglass, a high temperature resin, glass, an insulating or semi-insulating semiconductor, SiN, SiOx, Ta.sub.2O.sub.5. The mirror layer 204 may be any suitable reflective material and may, in some embodiments, be provided by the insulator layer 206 itself. The insulator layer 206 may also be provided by more than one layer, for example, Bragg reflectors may be incorporated into the insulator layers to provide a mirror. In other embodiments, the mirror layer 204 may be provided by an Al layer or other such reflective material.
[0416] The interconnection between contact pads 210 and 212 for the respective light emitting diode device contacts 110 and 112 may be provided as a metallization or other conductive pattern in/on the submount. For example, the interconnection could be provided as an aluminum pattern on the insulator layer 206. Alternatively or additionally, the interconnection could be provided as a conductive pattern within the insulator layer 206, for example, through the use of a damascene process where trenches are formed in the insulator layer 206, a metal layer is formed on the insulator layer 206 and in the trenches, and the metal layer is then planarized to remove portions of the metal layer that are not in the trenches, thus providing an interconnection pattern in the trenches. Alternatively, ITO (Indium and Tin Oxides) may be used as electrical conductive transparent interconnects.
[0417] By mounting the substrate 100 to the submount 200, a light emitter 10 is provided as a monolithic large area light emitter having the interconnection scheme illustrated in FIG. 5.
[0418] As is seen in FIG. 5, the light emitting diode devices 16 are connected in parallel subsets 12 that form rows in the array of devices. These rows of parallel diodes are connected in series to provide the high voltage light emitter 10. As discussed above, the interconnection of the diodes illustrated in FIG. 5 provides a high voltage device that may reduce FR losses, provide fault tolerance, improve device yields and allow for more efficient power supply designs.
[0419] FIGS. 6 through 9 are top views of submounts 200 and mechanically connected light emitting diode devices 16. In FIG. 6, the wafer portion 14 containing individual light emitting diode devices 16 have anode and cathode contacts 110 and 112 on opposite corners of the devices 16. The interconnection suitable for providing a monolithic high voltage light emitter 10 are illustrated in FIG. 7. As seen in FIG. 7, anode contact pads 212 and cathode contact pads 210 are configured such that the anodes 110 of subsequent devices in subsequent rows are connected to the cathode 112 of devices in previous rows by the diagonal interconnection patterns 216. The anodes 110 of devices in a first row of the device 10 are connected together to provide an anode contact 214 for the monolithic light emitter. The cathode contacts 112 of the last row of devices in the array are also connected together to provide a cathode contact 214 for the monolithic light emitter.
[0420] In FIG. 8, the individual light emitting diode devices 16 of the wafer portion 14 have anode and cathode contacts 110 and 112 disposed opposite each other on the devices 16. As seen in FIG. 9, this configuration of the contacts 110 and 112 may simplify the interconnection on the submount by allowing adjacent anode and cathode contacts 110 and 112 to be directly connected to each other by the contact pads 210 and 212 and the contacts of adjacent rows connected together by the interconnection 216.
[0421] FIG. 10 illustrates a high voltage light emitter where additional electrical circuitry, such as a drive transistor, is included on the submount assembly 300. As seen in FIG. 10, three contacts 322, 304 and 306 are provided to connect a transistor to the monolithic large area light emitter. A source contact 312 of a transistor may be connected to the cathode or anode of the monolithic large area light emitter. The other of the anode or cathode of the monolithic large area light emitter may be connected to a supply voltage or reference voltage (such as ground, possibly through a sense resistor which may also be provided on the submount) and the drain contact of the transistor connected to the other of the supply voltage or the reference voltage. A third contact 302 is provided for the gate of the transistor to control current flow through the monolithic large area light emitter. Additional components, such as capacitors, resistors and/or inductors, may also be provided on the submount to further facilitate operation of the monolithic large area light emitter. Such additional components can be attached to the submount or alternatively be fabricated as part of the submount in the case of the submount being a semiconductor material such as silicon or germanium. Other electrical circuits, such as electro-static discharge protection circuits, may also be provided.
[0422] FIG. 11 illustrates a self-contained high voltage light emitter 400. As seen in FIG. 11, the monolithic large area light emitter 420 may be provided on the submount 402 with additional light emitting devices 430. Additionally, power supply circuitry 410 may also, optionally, be provided on the submount 402. The power supply circuitry 410 may be an AC or DC power supply. The light emitting devices 430 and the monolithic large area light emitter 420 may be provided, for example, to provide the white light emitting system described in U.S. Pat. No. 7,213,940.
[0423] For example, the light emitter 400 may also include a submount 402 comprising an array of light emitting diode devices of one color 430 and a region of interconnects onto which is attached a monolithic array of light emitting diode devices of another color 420 and may also include a region of transistors and diodes and components to form part or all of a power supply 410 or control circuit. For example, the submount may comprise a GaAs or GaP layer with regions, such regions being delineated areas, including a region comprising layers of AlAs or AlInGaP or AlGaAs forming red orange or yellow light emitting diode devices or arrays of light emitting diode devices and interconnected, and preferably another region(s) where a monolithic arrays of blue and/or green and or cyan and or yellow light emitting diode devices can be mounted.
[0424] The embodiments described above provide for flip-chip mounting of the light emitting diode devices on the submount. However, in alternative embodiments, the light emitting diode devices may be mounted substrate side down to the submount. Such embodiments may utilize devices with, for example, a conducting substrate, such as a SiC substrate, with a via from the top side of the device to the back side of the device to provide both contacts on the same side of the device. Examples of such devices are illustrated in FIGS. 12 and 13. Alternatively, multiple vias could be utilized to move both top side contacts to the back side of the device if, for example, an insulating or semi-insulating substrate is used as described above.
[0425] As seen in FIGS. 12 and 13, a p contact 516 is provided on the backside of each device through a via 514 with insulating sidewalls. The insulating sidewalls prevent the contact from shorting across the P/N junction and the quantum wells. Thus, via 514 extends through the p-type layer 508, the quantum wells 506, the n-type layer 504, the buffer layer 502 and the substrate 500. The vias may be placed in the isolation region between light emitting diode devices so as to maximize the active area of the individual devices. Alternatively, the via could be placed through the active region of the device. In such a case, the isolation regions should still extend through the active regions of the device, i.e. the substrate, if the substrate is a conducting substrate, so as to allow for individual electrical connection of the light emitting diode devices.
[0426] In the devices illustrated in FIG. 12, the electrical interconnection of individual light emitting diode devices is provided by the submount. Thus, an electrical interconnection scheme such as illustrated in FIGS. 7 and 9 could be utilized. As seen in FIG. 12, the p-contact 516 can extend onto the p-type contact layer 508 or, alternatively or additionally, the p-contact 516 may be made on the sidewall of the p-type contact layer 508. Such a device may have a planar top surface and could maximize active area and reduce light obscuration by a contact. In any case, the periphery of the light emitting diode device could be ringed by the p-contact 516 so as to increase the surface area where the p-contact 516 is in contact with the p-type contact layer 508. In such a case, a non-conductive region 514 could be provided between adjacent light emitting diode devices so as to isolate the p-contacts of the mechanically connected devices.
[0427] In the devices illustrated in FIG. 13, electrical connection between mechanically connected devices within a row is made by the p-contact or adjacent devices. Mechanically connected devices from other rows would be isolated by a non-conductive region between the mechanically connected devices so that the array structure described above could be provided.
[0428] While not illustrated in FIGS. 12 and 13, an insulating layer could be provided on the back side of the wafer and contact holes opened in the insulating layer. Contact metal could then be filled into the contact holes to provide the p and n contacts illustrated. Such a metal contact could be provided by the damascene process described above and may provide a substantially planar surface for mounting to the submount.
[0429] FIG. 14 illustrates the devices of FIGS. 12 and 13 mounted on a submount to provide electrical interconnection into the array described above with reference to FIG. 5. As seen in FIG. 14, electrical contacts 526 and 528 and electrical interconnection may be provided on a submount substrate 520. The submount substrate 520 may be provided as any of the submount substrates discussed above. Likewise, the optional insulating and/or mirror layers 522 and 524 may also be provided as discussed above. The light emitting diode devices may be mounted on the submount substrate 520 through, for example, solder bumps 530 and 532 or other bonding technology between the p and n contacts 516 and 512 and the electrical contacts 526 and 528.
[0430] In addition to the electrical/mechanical bonding between the mechanically connected light emitting diode devices and the submount, a thermal connection material may also be provided. The thermal connection may be provided by the electrical and mechanical connection material or may be provided by a separate material. In some embodiments, an electrically non-conductive thermal material may be provided between the submount and the mechanically connected light emitting diode devices to improve heat extraction from the light emitting diode devices through the submount. Such a thermal material may also improve mechanical connection between the submount and the light emitting diode devices, and may also provide improved optical reflection or extraction from the light emitter. Examples of suitable materials include silicones or similar materials which may include particles or nanoparticles of thermally conductive material such as SiO.sub.2, AlOx, SiC, BeO, ZO.
[0431] FIG. 15 illustrates an interconnection of light emitting diode devices according to further embodiments of the present inventive subject matter. In the device of FIG. 15, two substrates 600 each mechanically interconnect corresponding sets of light emitting diode devices. The two substrates 600 are then mounted together such that anode contacts 610 of one set of light emitting diode devices on a first substrate 600 are electrically connected to cathode contacts 612 of a second set of light emitting diode devices on the second substrate 600. A first wire bond or other connection could be made to the first anode contact (on the left side of FIG. 15) and a second wire bond or other connection could be made to the last cathode contact (on the right side of FIG. 15). This would interconnect the light emitting diode devices of the two substrates into a series string of light emitting diode devices with an input at the first anode contact and an output at the last cathode contact. Otherwise, the buffer layer 602, the n-type layer 604, the quantum wells 606, the p-type layer 608 and the isolation regions 614 may be as described above with reference to any of the light emitting diode devices. Conductive regions 620 (e.g., solder regions, such as silver epoxy) are provided to provide electrical connection, and in some embodiments also mechanical bonding.
[0432] In order to provide parallel sets of light emitting diode devices in the series string, the light emitting diode devices in a given row on the two substrates 600 could be electrically interconnected by a metallization or shared p-contact layer in the dimension extending into and out of the page in FIG. 15. Such a potential electrical interconnection structure is seen in the top plan view of FIG. 16. In FIG. 16, adjacent light emitting diode devices have their respective anodes and cathodes 610 and 612 electrically coupled together such that when one of the two substrates 600 is flipped and mounted on the other (offset so that the anodes and cathodes line up) rows of parallel light emitting diode devices are electrically connected in series. Thus, by mounting one substrate on the other, an electrical circuit corresponding to that illustrated in FIG. 17 is provided.
[0433] FIG. 18 illustrates an embodiment of the present inventive subject matter where an interconnect layer 630, for example transparent or reflective, is provided between the substrates 600. The substrates 600 may be mechanically and electrically connected to the interconnect layer 630 such that the individual light emitting diode devices on the substrates are electrically connected in the array structure described herein. In such a case, the electrical interconnection between light emitting diode devices illustrated in FIG. 16 need not be provided and individual light emitting diode devices mechanically connected by a common substrate may be utilized. Suitable materials for such an interconnection layer 630 may be transparent ceramics, transparent oxides or transparent semi-conductors (insulating or semi-insulating) or glass with electrically conductive traces, such as Al, Au or the like, formed therein, or other materials known to those of skill in the art. The interconnect layer 630 may be one or more layers, as described herein with respect to the submount 200.
[0434] FIG. 19 illustrates embodiments of the present inventive subject matter that provide a stack of light emitting diode devices. In FIG. 19, vertical light emitting diode devices that are mechanically connected on a common substrate 700 are stacked and electrically interconnected such that light emitting diode devices on a common substrate 700 are electrically connected in parallel and then multiple substrates 700 are interconnected to provide a string of light emitting diode devices. The n-contact 710 and the p-contact 708 each extend across multiple devices to connect the devices in parallel. Conductive regions 714 (e.g., solder regions, such as silver epoxy) are provided to provide electrical connection, and in some embodiments also mechanical bonding. Thus, the circuit illustrated in FIG. 20 is provided by the substrate stack illustrated in FIG. 19.
[0435] While FIG. 19 illustrates vertical devices (e.g., an n contact 710 on an n-type conducting substrate 700 (which, by virtue of its n-type conductivity and its placement in the device, can also be referred to as an n-type layer), a conducting buffer layer 702, quantum wells 704, a p-type layer 706, a p-contact 708 and isolation regions 712) that are electrically connected in parallel at the substrate level, lateral devices or combinations of vertical and lateral devices could also be provided. For example, lateral devices with through vias to provide backside contacts could be utilized as well. Also, the vias need not be through vias, as illustrated in FIG. 21 where the n-contacts 812 of the lateral devices are made from the back side of the substrate 800. The devices of FIG. 21 may include an n contact 812, an insulating or semi-insulating substrate 800, a buffer layer 802, an n-type layer 804, quantum wells 806, a p-type layer 808, a p-contact 810 and isolation regions 814 as described above, for example, with reference to FIGS. 2 and 3. The n contacts 812 and the p contacts 810 may be connected using solder bumps 816 or other bonding techniques. Also illustrated in FIG. 21, a common p contact 810 is provided for multiple devices to connect the devices in parallel.
[0436] In addition to the interconnection illustrated in FIGS. 19 and 21, the interconnect layer described above with reference to FIG. 18 could also be utilized to connect, mechanically and electrically, stacks of substrates having a plurality of individual light emitting diode devices.
[0437] FIGS. 22 through 24 illustrate that the light emitting diode devices on the substrates need not all have the same shape and/or size and need not be rectangular or square. For example, FIG. 22 illustrates a light emitter 900 with one large light emitting diode device 906 surrounded by a plurality of smaller light emitting diode devices 904 on a common substrate 902. FIG. 23 illustrates a light emitter 920 with hexagonal light emitting diode devices 924 on a common substrate 922. FIG. 24 illustrates a light emitter 940 with a combination of square light emitting diode devices 946 and triangular light emitting diode devices 944 on a common substrate 942. Different configurations of the light emitting diode devices may be provided for any of a number of reasons. For example, different configurations may be provided to maximize the number of light emitting diode devices in a given area, to simplify interconnection or to improve thermal uniformity or heat extraction. For example, if it is more difficult to extract heat from light emitting diode devices in a particular portion of a substrate, light emitting diode devices in this portion could be made a different size to increase Vf and reduce current through the light emitting diode devices.
[0438] In each of the dies depicted in FIGS. 22-24, the die comprises a monolithic n-type layer comprising a plurality of n-type regions and a monolithic p-type layer comprising a plurality of p-type regions, wherein the n-type regions are isolated from each other by the isolation region, the p-type regions are isolated from each other by the isolation region, the n-type regions are positioned relative to each other in a manner which would prevent dicing the n-type layer into individual n-type regions with a conventional wafer cutting device (i.e., a conventional wafer cutting device would need to cut through the larger device in order to singulate all of the smaller devices), i.e., the n-type region (and the p-type region) of the large device extends across a line defined by the isolation region extending through the respective pairs of other n-type regions above the large device, below the large device, to the right of the large device and to the left of the large device.
[0439] FIG. 25 illustrates the ability to selectively electrically interconnect light emitting diode devices using any one of the submounts as described above. By coating or otherwise covering contact regions of an light emitting diode device with an insulator or material that prevents electrical connection and/or bonding to the submount, short circuited light emitting diode devices may be identified at the time of manufacture and eliminated from the array. Thus, FIG. 25 illustrates a light emitter 960 with a plurality of light emitting diode devices 964 on a common substrate 962. One of the light emitting diode devices 966 has been prevented from making contact with the submount so as to isolate the light emitting diode device 966. An inkjet or other selective application process or an insulating material may be used to selective isolate light emitting diode devices from the array. Alternatively, after identifying a shorted light emitting diode device, one or more of the contacts of the light emitting diode device could be removed to prevent electrical connection. Thus, shorting across a row of light emitting diode devices in the array may be avoided and the overall voltage across the array may be maintained.
[0440] FIG. 25 illustrates that the middle light emitting diode device 966 in the second row has been identified as shorted and isolated such that the light emitting diode device 966 will not be connected in the array when the monolithic large area substrate 962 is mounted to the interconnection submount. Such isolation of a defective device may provide means for healing defects in an array of devices on a common substrate. Operations for the identification and isolation of light emitting diode devices within an array are illustrated in FIG. 26.
[0441] In FIG. 26, operations begin by electrically testing a light emitting diode device on the common substrate (block 1000). Such a test may, for example, be carried out with an automated probe that individually activates each light emitting diode device. The electrical test may measure any number of electrical or photonic characteristics of the device but, for purposes of interconnection, may determine if the individual light emitting diode device is shorted. Such a test is preferably performed after all processing steps are performed that could potentially cause such a short. If the light emitting diode device is shorted (block 1010), then the light emitting diode device is isolated (block 1020) so as to not make a connection to other light emitting diode devices in the array. Such an isolation may be performed as discussed above, for example, by inkjet printing of an insulating material, by etching to remove one or more contact using, for example, a stepper mask or other suitable technique known to those of skill in the art. If more light emitting diode devices are to be evaluated (block 1030) the process can be repeated from block 1000. When all light emitting diode devices have been evaluated (block 1030), the monolithic structure may be mounted to the submount to electrically interconnect the individual light emitting diode devices (block 1040).
[0442] The operations illustrated in FIG. 26 may be performed before or after the monolithic collection of devices is separated from the wafer. In addition, the separation of portions of a wafer into individual monolithic light emitters which have a plurality of mechanically connected light emitting diode devices can be carried out based on the locations of defective parts so as to increase the yield of such monolithic light emitters.
[0443] Furthermore, while the operations illustrated in FIG. 26 are described with reference to a linear step-wise process, operations may be performed in parallel or out of turn as long as the overall operations achieve the desired result of selectively isolating defective light emitting diode devices. Thus, for example, all light emitting diode devices on a common substrate could be activated at once, and the electrical characteristics measured in parallel. Thus, embodiments of the present inventive subject matter should not be construed as limited to the particular sequence of operations illustrated in FIG. 26.
[0444] FIG. 27 illustrates a further example of a submount according to some embodiments that provide means for healing a defect in a device. In the submount 1100 illustrated in FIG. 27, adjacent cathode contacts 1104 and anode contacts 1106 in a row are connected through a fused link 1106 in/on the submount substrate 1102. The fused link 1106 may be set such that if all of the current that flows through the array flows through the link, the fuse will open. Thus, if a light emitting diode device in a row short circuits, the fuse 1110 will open and the current will be redirected through the remaining light emitting diode devices in the row through the interconnection 1108. If all but one of the light emitting diode devices in the row short circuit, then the last light emitting diode device will carry the entire current, and the fuse 1110 will open for that light emitting diode device and the entire light emitter will be open circuited (at which point the light emitter will no longer function).
[0445] A lighting system is also provided that includes a boost power supply having an output voltage that is greater than a corresponding input voltage, and a light emitter. The light emitter includes a plurality of light emitting devices from a contiguous region of a wafer of light emitting devices, the plurality of light emitting devices being electrically connected as a plurality of serially connected subsets of at least three parallel connected light emitting devices electrically coupled to the output voltage of the boost power supply. The boost power supply may be configured to be coupled to an AC power source to provide the input voltage. Boost power supply configurations are known to those of skill in the art. Boost power supplies may be highly efficient. Furthermore, as discussed above, by providing a high voltage light emitter, I.sup.2R losses may be reduced because the current through the light emitter may be reduced in comparison to corresponding lower voltage light emitters. Combining the high voltage light emitter as described herein with a boost power supply may provide very high system efficacies. Thus, in some embodiments of the present inventive subject matter, the high voltage light emitters are provided to operate at a voltage of at least 50 volts, at least 150 volts, at least 325 volts or at least 395 volts. The operating voltage of the high voltage light emitter may be controlled by the forward voltage drop of the individual devices and the number of subsets of parallel-connected devices that are connected in series. Thus, for example, if a 90 volt device is desired, 30 subsets of devices, each with a V.sub.f of 3 volts, could be connected in series.
[0446] Representative examples of circuits which include a boost component are described in U.S. Patent Application No. 60/844,325, filed on Sep. 13, 2006, entitled BOOST/FLYBACK POWER SUPPLY TOPOLOGY WITH LOW SIDE MOSFET CURRENT CONTROL (inventor: Peter Jay Myers; attorney docket number 931_020 PRO), and U.S. patent application Ser. No. 11/854,744 (now U.S. Patent Application Publication No. 2008/0088248), filed Sep. 13, 2007, the entireties of which are hereby incorporated by reference.
[0447] While embodiments of the present inventive subject matter have been described with reference to a multi-quantum well structure, the present inventive subject matter may be utilized with any suitable light emitting diode device configuration(s). Furthermore, light extraction enhancements, such as internal reflecting layers, transparent ohmic contacts and the like may be utilized to improve light extraction from the individual light emitting diode devices. Accordingly, embodiments of the present inventive subject matter should not be construed as limited to a particular light emitting diode device configuration, but may be used with any configuration capable of being mounted to a submount for electrical interconnection to provide a high voltage monolithic light emitter.
[0448] The light emitters of the present inventive subject matter can be supplied with electricity in any desired manner. Skilled artisans are familiar with a wide variety of power supplying apparatuses, and any such apparatuses can be employed in connection with the present inventive subject matter. The light emitters of the present inventive subject matter can be electrically connected (or selectively connected) to any desired power source, persons of skill in the art being familiar with a variety of such power sources.
[0449] While inventive aspects have been described above primarily with reference to monolithic devices for operation with DC power sources, additional inventive aspects may provide monolithic devices suitable for operation with AC and/or DC power sources. Examples of such devices are illustrated in FIGS. 28 and 29.
[0450] FIG. 28 illustrates an AC monolithic device 1100. The AC monolithic device 1100 includes a plurality of light emitting diodes 1110 provided as two or more arrays 1114, 1116 of serially connected subsets 1112 of parallel connected light emitting diodes 1110. The diodes 1110 may be interconnected as described elsewhere herein. The diodes 1110 may have a common substrate and/or be formed from a common n-type or p-type layer. The arrays 1114 and 1116 may be electrically arranged in an anti-parallel relationship such that when an alternating current (AC) power source is applied to the two arrays 1114, 1116, substantially all of the current flows through only one of the arrays on alternating cycles of the AC input. Thus, the monolithic device 1100 may be suitable for use as an AC device. The expression anti-parallel, as used herein, refers to circuitry in which arrays of diodes are arranged in parallel, with the diodes in at least one array being oriented (biased) in a direction which is opposite to the direction of orientation (bias) of the diodes in at least one other array (as shown in the circuit depicted in FIG. 28).
[0451] The monolithic device 1100 may be made using any of the fabrication techniques described herein that are capable of providing the interconnections illustrated in FIG. 28. The number of serially connected subsets 1112 of light emitting diodes 1110 may be selected based on the desired operating voltage. Also, the number of light emitting diodes 1110 that are connected in parallel may be selected as described above and should include at least three parallel connected devices.
[0452] FIG. 29 illustrates a monolithic device 2000 that may receive an AC or DC input. In particular, the monolithic device 2000 includes a rectifying bridge 2020 and one or more arrays 2010 of serially connected subsets 2012 of parallel connected light emitting devices. The rectifying bridge 2020 may be constructed of light emitting devices 2022. The light emitting devices 2022 may be formed on a common substrate, from a common n-type or p-type layer or from a common material system, such as SiC, GaN, etc., as the light emitting devices in the array 2010. The diodes 2022 may also be non-light emitting. The number of diodes 2022 in each leg of the bridge 2020 depends on the reverse breakdown characteristics of the diodes and should be sufficient to support the reverse voltage from alternating cycles of the AC input. While the diodes 2022 are shown as two diodes serially connected, other numbers of diodes may be utilized. Furthermore, the diodes 2022 of the bridge 2020 may be provided as serially connected subsets of parallel connected diodes as described herein.
[0453] The output of the bridge 2020 is a full wave rectified voltage that is provided to the array 2010. As described above, the number of serially connected devices in the array 2010 may be selected based on the operating voltage provided by the bridge 2020.
[0454] The monolithic device 2000 may be provided using any suitable fabrication and interconnection technique as described above. Furthermore, while the monolithic device is illustrated in FIG. 29 with an AC input, a DC input could be applied to the device.
[0455] Furthermore, while certain embodiments of the present inventive subject matter have been illustrated with reference to specific combinations of elements, various other combinations may also be provided without departing from the teachings of the present inventive subject matter. Thus, the present inventive subject matter should not be construed as being limited to the particular exemplary embodiments described herein and illustrated in the Figures, but may also encompass combinations of elements of the various illustrated embodiments.
[0456] Many alterations and modifications may be made by those having ordinary skill in the art, given the benefit of the present disclosure, without departing from the spirit and scope of the inventive subject matter. Therefore, it must be understood that the illustrated embodiments have been set forth only for the purposes of example, and that it should not be taken as limiting the inventive subject matter as defined by the following claims. The following claims are, therefore, to be read to include not only the combinations of elements which are literally set forth but all equivalent elements for performing substantially the same function in substantially the same way to obtain substantially the same result. The claims are thus to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, and also what incorporates the essential idea of the inventive subject matter.
[0457] Any two or more structural parts of the light emitters described herein can be integrated. Any structural part of the light emitters described herein can be provided in two or more parts (which are held together, if necessary). Similarly, any two or more functions can be conducted simultaneously, and/or any function can be conducted in a series of steps.
