Semiconductor component with radiation conversion element, and method for producing radiation conversion elements

Abstract

The invention relates to a semiconductor component with a semiconductor chip and a radiation conversion element which is arranged on the semiconductor chip. The semiconductor chip has an active region which is designed to generate a primary radiation with a peak wavelength, the radiation conversion element has a quantum structure, the peak wavelength of the primary radiation lies in the infrared spectral range, and the quantum structure at least partly converts the primary radiation into a secondary radiation, wherein the emission wavelength of an emission maximum of the secondary radiation is greater than the peak wavelength. The invention additionally relates to a method for producing radiation conversion elements.

Claims

1. A semiconductor component having a semiconductor chip and a radiation conversion element, which is arranged on the semiconductor chip, wherein the semiconductor chip comprises an active region intended to generate primary radiation with a peak wavelength; the radiation conversion element comprises a monocrystalline quantum structure, positioned directly on a substrate of the semiconductor chip; the quantum structure comprises a multiplicity of quantum layers, which are separated from one another by barrier layers and the quantum structure comprises at least one material from the group of the following material systems: Gax In1-x Asy P1-y, Inx Ga1-x Asy Sb1-y, Inx Ga1-x As, Inx Ga1-x Py Sb1-y, Inx Al1-x Py Sb1-y, where x and y are respectively selected so that a lattice constant of the material corresponds to that of InP; the peak wavelength of the primary radiation lies in the infrared spectral range; and the quantum structure converts the primary radiation at least partially into secondary radiation, an emission wavelength of an emission maximum of the secondary radiation being greater than the peak wavelength; wherein the radiation conversion element only partially covers at most 80% the active region.

2. The semiconductor component as claimed in claim 1, wherein the barrier layers have a band gap which is greater than an energy of the radiation with the peak wavelength.

3. The semiconductor component as claimed in claim 1, wherein the quantum structure comprises at least two quantum layers, which differ from one another in terms of their band gap.

4. The semiconductor component as claimed in claim 1, wherein the quantum structure has a lattice constant of InP.

5. The semiconductor component as claimed in claim 1, wherein the radiation conversion element covers at most 80% of the active region of the semiconductor chip in a plan view of the semiconductor component.

6. The semiconductor component as claimed in claim 1, wherein the radiation conversion element covers at least 90% of the active region of the semiconductor chip in a plan view of the semiconductor component.

7. The semiconductor component as claimed in claim 1, wherein the radiation conversion element has a thickness of at most 200 m.

8. The semiconductor component as claimed in claim 1, wherein the semiconductor chip comprises a carrier and a mirror layer is arranged between the active region and the carrier.

9. A method for producing a multiplicity of radiation conversion elements comprising: a) depositing a semiconductor layer sequence having a monocrystalline quantum structure directly on a substrate; and b) dividing the semiconductor layer sequence into the multiplicity of radiation conversion elements; and wherein the quantum structure comprises at least one material from the group of the following material systems: Gax In1-x Asy P1-y, Inx Ga1-x Asy Sb1-y, Inx Ga1-x As, Inx Ga1-x Py Sb1-y, Inx Al1-x Py Sb1-y, where x and y are respectively selected so that a lattice constant of the material corresponds to that of InP; and wherein the multiplicity of radiation conversion elements only partially covers at most 80% an active region of a corresponding semiconductor chip.

10. The method as claimed in claim 9, wherein the substrate is at least partially removed from the quantum structure.

11. The method as claimed in claim 10, wherein a sacrificial layer is removed.

12. The method as claimed in claim 10, wherein separation nuclei are introduced into the substrate and a part of the substrate is separated along the separation nuclei.

13. The method as claimed in claim 9, wherein at least a part of the substrate is reused for step a) in a further production cycle of the method.

14. The method as claimed in claim 9, wherein the substrate is thinned before step b).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further configurations and expediencies may be found from the following description of the exemplary embodiments in conjunction with the figures, in which:

(2) FIGS. 1A, 1B, 1C, 1D and 1E show exemplary embodiments of a semiconductor component in a schematic sectional view (FIG. 1A) or in a schematic plan view (FIGS. 1B to 1E);

(3) FIGS. 2A and 2B respectively show schematic representations of exemplary embodiments of a band structure of a radiation conversion element;

(4) FIGS. 3A, 3B, 3C and 3D respectively show an exemplary embodiment of an emission spectrum of the semiconductor component;

(5) FIG. 4 shows an illustration of possible emission wavelengths achievable with different semiconductor material systems, the band gap E.sub.G (left scale) and the associated emission wavelength (right scale) being represented as a function of the lattice constants d;

(6) FIG. 5A shows examples of measurement data for the intensity in arbitrary units as a function of the wavelength for different light-emitting diodes;

(7) FIG. 5B shows examples of measurement data for the intensity as a function of the wavelength for a light-emitting diode with two different currents, on a linear scale in arbitrary units (left) and on a corresponding logarithmic scale (right);

(8) FIG. 5C shows examples of electro-optical intensity measurements in arbitrary units from two epitaxial substrates with different quantum structures as a function of the wavelength;

(9) FIGS. 6A to 6C, 7A to 7C, 8A to 8D and 9A to 9D respectively show an exemplary embodiment of a method for producing radiation conversion elements, with the aid of schematically represented intermediate steps.

DETAILED DESCRIPTION

(10) Elements which are the same, or of the same type, or which have the same effect, are provided with the same references in the figures.

(11) The figures are respectively schematic representations and are therefore not necessarily true to scale. Rather, relatively small elements, and in particular layer thicknesses, may be represented as being exaggeratedly large for illustration.

(12) FIG. 1A represents an exemplary embodiment of a semiconductor component 1 in a sectional view along the line AA shown in FIG. 1B. The semiconductor component 1 comprises a semiconductor chip 2 having an active region 20 intended for generating primary radiation. The active region is located between a first semiconductor layer 21 and a second semiconductor layer 22 of the semiconductor chip. For example, the first semiconductor layer 21 is n-conductive and the second semiconductor layer 22 is p-conductive, or vice versa. By application of an external electrical voltage between one contact 45 and a further contact 46 of the semiconductor chip, charge carriers from opposite sides can enter the active region 20 through the first semiconductor layer 21 and the second semiconductor layer 22 and recombine there while emitting primary radiation.

(13) A radiation conversion element 3 is arranged on the semiconductor chip 2. The radiation conversion element 3 is fastened on the semiconductor chip 2 by a bonding layer 4. For example, the bonding layer contains a silicone or an epoxide. The bonding layer 4 is expediently transparent for the radiation generated in the active region 20.

(14) The radiation conversion element 3 comprises a quantum structure 30. For simplified representation, two quantum layers 31 and two barrier layers 32 are shown in FIG. 1A. The number of quantum layers may however vary in wide limits, for example between one quantum layer inclusive and 50 quantum layers inclusive.

(15) The quantum structure 30 is arranged on a substrate 35 of the radiation conversion element 3. For example, the substrate is a growth substrate for the deposition, in particular epitaxial deposition, of the quantum structure 30. The growth substrate for the semiconductor layers of the quantum structure 30 must be contained in the semiconductor component 1, although not fully, but may fully or partially have been removed during the production of the radiation conversion element 3.

(16) A peak wavelength of the primary radiation lies, for example, in the infrared spectral range. For example, the peak wavelength lies between 920 nm inclusive and 1070 nm inclusive, in particular between 940 nm inclusive and 1000 nm.

(17) For example, the active region 20 of the semiconductor chip 2 is based on the material system In.sub.x Ga.sub.y Al.sub.1-x-y As.sub.z P.sub.1-z. The parameters x, y and z of the material composition are, in particular, selected so that the material may be deposited in a monocrystalline fashion on a GaAs substrate as the growth substrate.

(18) In the exemplary embodiment shown, the semiconductor chip 2 is configured as a thin-film semiconductor chip in which the growth substrate for the semiconductor layer sequence with the active region 20 is no longer present in the completed semiconductor chip. The semiconductor layer sequence with the active region 20 is fastened on a carrier 29 by means of a connecting layer 26. The carrier 29 itself need not satisfy the stringent requirements for the crystalline purity of a growth substrate. A mirror layer 25, in particular a metallic mirror layer, is furthermore arranged between the active region 20 and the carrier 29, so that radiation generated in the active region 20 and emitted in the direction of the carrier 29 is reflected and emerges at a radiation emission face 200 of the semiconductor chip 2, which lies opposite the carrier 29.

(19) The primary radiation generated in the active region 20 is at least partially converted into secondary radiation in the quantum structure 30 of the radiation conversion element 3.

(20) The barrier layers are preferably selected in terms of their material composition in such a way that they have a band gap which is greater than an energy of the radiation of the primary radiation with the peak wavelength. This is represented in FIG. 2A with the aid of a schematic representation of a valence band E.sub.V and conduction band E.sub.C of the quantum structure 30. The primary radiation 5, represented by an arrow, is absorbed not in the barrier lavers 32 but in the quantum layers 31. An excitation 51 resulting therefrom is illustrated by an arrow.

(21) The secondary radiation 6 may subsequently be emitted with a longer wavelength, represented by an arrow. This emission takes place, for example, from a ground state of a quantum well formed by the quantum layer. Direct optical excitation of the quantum layers 31, and therefore particularly efficient radiation conversion, thus take place.

(22) In the exemplary embodiment represented in FIG. 2A, the band gaps of the quantum layers 31 do not differ from one another, or differ only slightly. This leads to a spectrally narrow-band emission spectrum.

(23) In contrast thereto, FIG. 2B shows an exemplary embodiment in which at least two quantum layers 31 differ from one another in terms of their band gap. The emission spectrum of the semiconductor component may be adapted simply and reliably to a predetermined emission characteristic by the selection of the material parameters for the quantum layers 31 of the quantum structure.

(24) FIGS. 3A to 3D show various configurations of the emission spectrum of the semiconductor component, the intensity in arbitrary units respectively being represented as a function of the wavelength . The lines 901 respectively represent the primary radiation and the lines 902 respectively represent the secondary radiation. In the exemplary embodiment represented in FIG. 3A, the secondary radiation has precisely one emission maximum, which represents a global maximum.

(25) By mutually different quantum layers however, as represented in FIG. 3B, it is also possible to achieve an emission spectrum in which the secondary radiation has two or more mutually separated emission bands with mutually different emission maxima 9021 and 9022, respectively. For example, the spectral distance between two emission maxima 9021, 9022 may be greater than the sum of the half widths at half maximum (HWHM) of the emission bands, so that the emission spectrum has emission maxima that are significantly different to one another in the secondary radiation.

(26) As an alternative, the distance between neighboring emission maxima may also be smaller, as is represented in FIG. 3C. In this case, the emission maxima 9021, 9022 and 9023 may be superimposed to form a common spectrally broadened emission peak, so that the semiconductor component 1 is spectrally distinguished by particularly broad emission. The emission spectrum of the secondary radiation may thus be broadened by deliberate variation of the quantum layers.

(27) The spectrum of the primary radiation 901 may also, as illustrated in FIG. 3D, have more than one emission maximum, for example one emission maximum 9011 and a further emission maximum 9012.

(28) Materials which can be deposited epitaxially on InP are particularly suitable for the quantum structure 30.

(29) For example, the quantum structure comprises at least one material from the group of the following material systems: Ga.sub.x In.sub.1-x As.sub.y P.sub.1-y, In.sub.x Ga.sub.1-x As.sub.y Sb.sub.1-y, In.sub.x Ga.sub.1-x As, In.sub.x Ga.sub.1-x P.sub.y Sb.sub.1-y, In.sub.x Al.sub.1-x P.sub.y Sb.sub.1-y, where x and y are respectively selected so that the lattice constant of the material corresponds to, or is at least close to, that of InP. In particular, a peak wavelength which is at least 920 nm, for example at least 930 nm or at least 940 nm, is suitable for the primary radiation, so that the primary radiation is not absorbed by an InP substrate 35 of the radiation conversion element 3 and barrier layers 32 made of the same material.

(30) The proportion of the primary radiation in the emission spectrum of the semiconductor component 1 may also be adjusted by means of the degree of coverage of the radiation emission face 200 of the semiconductor chip 2 by the radiation conversion element 3. This is illustrated with the aid of FIGS. 1B to 1E. In the exemplary embodiment represented in FIG. 1B, the semiconductor chip 2 comprises a front-side contact 45 in a corner region of the semiconductor chip 2. The radiation conversion element 3 comprises a recess 39 so that the contact 45 is accessible for the external electrical contacting of the semiconductor component 1, for example by means of a wire bond connection. The active region 20 is fully covered, or at least substantially fully covered, for example with a degree of coverage of at least 90. The primary radiation emerging through the radiation emission face 200 thus has to pass through the radiation conversion element 3 before it can emerge at a front side 10 of the semiconductor component 1.

(31) In contrast thereto, the radiation conversion element 3 in the exemplary embodiment represented in FIG. 1C covers the active region 20 of the semiconductor chip 2 only partially, for example with a degree of coverage of at most 80% or at most 60%. A significant proportion of the primary radiation therefore emerges laterally with respect to the radiation conversion element 3 at the front side 10 of the semiconductor component 1. This is favorable in particular when the primary radiation is desired in the emission spectrum of the semiconductor component 1.

(32) The exemplary embodiments in FIGS. 1D and 1E differ from the exemplary embodiments according to FIGS. 1B and 1C in that the contact 45 extends not in a corner region but along a side face 27 of the semiconductor chip 2. In the exemplary embodiment represented in FIG. 1D, as described in connection with FIG. 1C, the radiation conversion element 3 covers the active region 20 of the semiconductor chip 2 only regionally, so that a significant proportion of the radiation emission face of the semiconductor chip 2 remains without the radiation conversion element. In the exemplary embodiment represented in FIG. 1E, the radiation emission face is covered fully, or substantially fully, by the radiation conversion element 3. For this, the radiation conversion element may have a simple shape, for example rectangular.

(33) FIG. 4 illustrates the emission wavelength which may be achieved with particular material systems. The lines 905 and 906 in this case illustrate the lattice constant of gallium arsenide or indium phosphide. It may be seen therefrom that emission in the spectral range of between 1000 nm inclusive and 1700 nm inclusive is not readily achievable with the lattice constant of gallium arsenide. In contrast to the other material systems represented, the material system of the nitride semiconductors 990 with the vertices InN, GaN and AlN grows not in the zinc blende structure but in the wurtzite structure, and is therefore not readily combinable with the other material systems represented.

(34) With the lattice constant of InP, however, a spectral range of between 1000 nm inclusive and 1700 nm inclusive is achievable. This is illustrated with the aid of an arrow 908 between two lines 907.

(35) FIG. 5A represents measurements of the intensity of the emitted radiation for different light-emitting diodes, which were respectively deposited on a GaAs substrate. While radiation with a peak wavelength of between 950 nm and 1000 nm can be generated efficiently, the intensity decreases significantly for comparative samples with peak wavelengths greater than 1000 nm. This material system is thus only limitedly suitable for direct radiation generation with peak wavelengths greater than 1000 nm.

(36) FIG. 5B represents measurements of the intensity as a function of the wavelength for a light-emitting diode with two different operating currents. For this light-emitting diode, the layer thicknesses were increased in the active region for some quantum layers. This leads to two emission bands, which are separated from one another by about 15 nm. This results in a broadened emission spectrum. This procedure may also be applied to the quantum structure of the described radiation conversion element and to other emission wavelengths, so that a broadened emission spectrum of the secondary radiation may be achieved (cf. FIG. 3C).

(37) FIG. 5C represents electro-optical measurements for two substrates on which two active regions, which are electrically connected to one another via a tunnel junction, are respectively deposited. Curve 910 is based on a structure in which a first active region comprises quantum layers for emission at 810 nm and quantum layers for emission at 1020 nm. A second active region comprises quantum layers for emission at 850 nm and quantum layers for emission at 940 nm. This procedure may also be applied to the quantum structure of the described radiation conversion element and to other emission wavelengths, so that an emission spectrum of the secondary radiation with individual, mutually separated emission bands may be achieved (cf. FIG. 3D).

(38) Curve 920 is based on a modified structure in which some quantum layers of the emission bands at 810 nm and 850 nm have deliberately been configured with a larger layer thickness. This leads to additional emission at somewhat longer wavelengths. The spectrum thus has individual emission bands, the emission peaks in part being deliberately broadened.

(39) Overall, the measurement results of FIGS. 5B and 5C confirm the great flexibility in the configuration of the emission spectrum of a quantum structure.

(40) FIGS. 6A to 6C describe an exemplary embodiment of a method for producing a radiation conversion element. As represented in FIG. 6B, a semiconductor layer sequence 300 having a quantum structure 30 is epitaxially deposited on a substrate 35. Division into a multiplicity of radiation conversion elements 3 is then carried out. The division is carried out for example mechanically, for instance by sawing, chemically, for instance by etching, or by means of laser separation.

(41) Recesses for the radiation conversion elements to be produced may also be formed before or during the division. Radiation conversion elements which do not have a rectangular cross section may thus be produced in a straightforward way (compare the radiation conversion element 3 represented in FIG. 1B with the recess 39).

(42) The radiation conversion elements produced in this way may in other regards be configured as described in connection with the preceding figures, and will therefore not be explained in detail here.

(43) The divided radiation conversion elements 3 may subsequently be placed and fastened on semiconductor chips in order to produce semiconductor components.

(44) The size of the substrates 35 for the radiation conversion elements 3 is therefore independent of the size of the substrates on which the production of the semiconductor chips is carried out. For example, more economical 4 substrates may be used for the radiation conversion elements even if the production of the semiconductor chips is carried out on the basis of 6 processes.

(45) The exemplary embodiment represented in FIGS. 7A to 7C differs from the exemplary embodiment described in connection with FIGS. 6A to 6C in that the substrate 35 is thinned, for example by a mechanical method such as grinding (FIG. 7B), after the deposition of the quantum structure 30 (FIG. 7A). The division is then carried out (FIG. 7C). In this way, the thickness of the substrate remaining in the radiation conversion element 3 may be reduced. The smaller the thickness of the substrate is, the lower the proportion of the radiation which emerges laterally from the radiation conversion element can be.

(46) For example, the radiation conversion element has a thickness of at most 200 m after the thinning.

(47) FIGS. 8A to 8D describe a method by which the radiation conversion elements 3 can be produced without the original substrate. For this, a sacrificial layer 37 is arranged between the substrate 35 and the quantum structure 30 (FIG. 8B). This sacrificial layer may subsequently be removed, for example by a selective etching method, so that the quantum structure 30 and the substrate 35 are separated from one another (FIG. 8C).

(48) The separation of the quantum structure and the substrate is expediently carried out before the division (FIG. 8D), so that the substrate 35 may be used again for the deposition of a semiconductor layer sequence in a further production cycle. By this re-use of the relatively expensive growth substrate, the production costs for the radiation conversion element may be reduced further. Furthermore, particularly thin radiation conversion elements may be produced.

(49) In the exemplary embodiment described in FIGS. 9A to 9D, the substrate 35 comprises separation nuclei 38. These separation nuclei may, for example, be introduced into the substrate by ion implantation. For example, implantation of hydrogen ions is suitable.

(50) This may already be carried out before the deposition of the semiconductor layer sequence for the quantum structure 30 (FIG. 9B). In contrast thereto, it is also conceivable to deposit the quantum structure 30 first and to form the separation nuclei 38 subsequently.

(51) The substrate 35 may be split along the separation nuclei 38, for example by thermal splitting (FIG. 9C). A separated part 351 of the substrate is thereby formed.

(52) The division may finally be carried out as described in the preceding exemplary embodiments (FIG. 9D).

(53) The separated part 351 may be used again as described in connection with FIGS. 8A to 8D, optionally after preparing the surface of the substrate.

(54) With the described semiconductor component 1 and the described production method, radiation in the infrared spectral range, in particular between 1000 nm inclusive and 1700 nm inclusive, may be generated particularly efficiently. The emission spectrum may be adapted straightforwardly to the respective applications for the semiconductor component, in particular by selection of the material composition and layer thicknesses for the quantum layers of the quantum structure.

(55) For example, the semiconductor components are suitable as light sources for analytical applications, for example for the detection of water or moisture. The secondary radiation may form the emission spectrum of the semiconductor component on its own, or it may be present in addition to the primary radiation.

(56) Furthermore, particularly in combination with a semiconductor chip 2 configured as a thin-film semiconductor chip, predominant radiation emission may be achieved on the front side of the semiconductor component so that the spatial emission characteristic may be shaped more simply by means of a downstream optical element.

(57) Thin-film technology in which GaAs growth substrates are removed may be used for this.

(58) The invention is not restricted by the description with the aid of the exemplary embodiments. Rather, the invention comprises any new feature and any combination of features, which in particular includes any combination of features in the claims, even if this feature or this combination itself is not explicitly specified in the claims or exemplary embodiments.