An Optoelectronic Apparatus

Abstract

In an embodiment an optoelectronic apparatus includes a light detector having a bottom side, an upper side and at least one sidewall that extends between the upper side and the bottom side, a carrier having an upper surface on which the light detector is arranged such that the bottom side faces the carrier, at least one outer wall which is arranged on the surface of the carrier, the outer wall and the carrier forming a cavity with an opening in which the light detector resides, a filter covering the upper side of the light detector, the filter having a first threshold wavelength separating a first wavelength region from an adjacent second wavelength region, wherein the filter has a lower transmittance for light at wavelengths in the first wavelength region than for light at wavelengths in the second wavelength region and a first material layer covering the filter.

Claims

1.-18. (canceled)

19. An optoelectronic apparatus comprising: a light detector having a bottom side, an upper side and at least one sidewall that extends between the upper side and the bottom side; a carrier having an upper surface on which the light detector is arranged such that the bottom side faces the carrier; at least one outer wall which is arranged on the surface of the carrier, the outer wall and the carrier forming a cavity with an opening in which the light detector resides; a filter covering the upper side of the light detector, the filter having a first threshold wavelength separating a first wavelength region from an adjacent second wavelength region, wherein the filter has a lower transmittance for light at wavelengths in the first wavelength region than for light at wavelengths in the second wavelength region; and a first material layer covering the filter, wherein the first material layer is configured to have a higher absorbance for light at wavelengths in a third wavelength region than for light at wavelengths in an adjacent fourth wavelength region, wherein a second threshold wavelength separates the third and fourth wavelength regions from each other, and wherein that the first threshold wavelength at least approximately corresponds to the second threshold wavelength.

20. The optoelectronic apparatus of claim 19, wherein the first threshold wavelength differs from the second threshold wavelength by at most ±20 nm.

21. The optoelectronic apparatus of claim 19, wherein the filter is a dielectric filter or comprises a resist material, and/or wherein the first material layer comprises epoxy or silicone and absorber particles which act as a filter.

22. The optoelectronic apparatus of claim 19, wherein the outer wall extends at a distance in a circumferential direction around the at least one sidewall of the light detector, and/or wherein the outer wall is configured to absorb light at wavelengths below and above the first threshold wavelength, and/or wherein the outer wall is blackened or darkened.

23. The optoelectronic apparatus of claim 19, further comprising: a second material layer comprising a highly absorbing casting material, the second material layer arranged between the first material layer and the carrier, wherein the second material layer covers completely the at least one sidewall of the light detector and/or the upper surface of the carrier.

24. The optoelectronic apparatus of claim 23, wherein the second material layer is arranged in a volume formed by the first material layer, the upper surface of the carrier, and at least one outer wall which extends on the upper surface of the carrier in a circumferential direction around the at least one sidewall of the light detector.

25. The optoelectronic apparatus of claim 23, wherein the second material layer is configured to absorb light at wavelengths below and above the first threshold wavelength.

26. The optoelectronic apparatus of claim 19, wherein the filter is formed by a third material layer comprising a resist material, and wherein the third material layer covers the upper side and the at least one sidewall of the light detector.

27. The optoelectronic apparatus of claim 26, wherein the third material layer is arranged between the first material layer and the carrier, and/or wherein the third material layer is the only layer arranged between the first material layer and the carrier, and/or wherein the third material layer has a thickness that is larger than a height of the light detector.

28. The optoelectronic apparatus of claim 19, further comprising a fourth material layer comprising a resist, the fourth material layer arranged above the first material layer.

29. The optoelectronic apparatus of claim 28, wherein the fourth material layer has a higher absorbance for light at wavelengths in a fifth wavelength region than for light at wavelengths in an adjacent sixth wavelength region, wherein a third threshold wavelength separates the fifth and sixth wavelength regions from each other, wherein the first threshold wavelength at least approximately corresponds to the third threshold wavelength, and wherein the first threshold wavelength differs from the third threshold wavelength by at most ±20 nm.

30. The optoelectronic apparatus of claim 19, wherein at least one of the first material layer, a second material layer, a third material layer or a fourth material layer covers completely a full width and a full height of the opening of the cavity that is formed by the carrier and the at least one outer wall.

31. The optoelectronic apparatus of claim 19, wherein in the second wavelength region the filter and the first material layer have in combination a transmittance of at least 80% with respect to an intensity of an incident light, and/or wherein the filter and the first material layer have in combination a transmittance of less than 80% in the first wavelength region.

32. The optoelectronic apparatus of claim 19, wherein the filter and the first material layer act as a combined filter having a cut-on or cut-off wavelength that is shifted with regard to the first threshold wavelength by at most 20 nm for angles of incidence in a range of 0° to 60° and by at most 30 nm for angles of incidence in a angel of 0° to 90°.

33. The optoelectronic apparatus of claim 19, further comprising a clear resin arranged between the light detector and the filter and the first material layer.

34. A package module comprising: one or more light sources; and one or more optoelectronic apparatuses of claim 19.

35. The package module of claim 34, wherein at least one of the light sources is configured to provide light having a wavelength in the first wavelength region, and/or wherein the one or more light sources do not provide light with a wavelength in the second wavelength region.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order that the invention may be more fully understood, exemplary embodiments thereof will now be described by way of example only, with reference to the accompanying drawings, in which:

[0038] FIG. 1 shows schematically a cross-sectional view of a first exemplary embodiment of an optoelectronic apparatus in accordance with embodiments of the present invention;

[0039] FIG. 2 shows schematically a perspective view of the optoelectronic apparatus of FIG. 1;

[0040] FIG. 3 shows schematically a cross-sectional view of a second exemplary embodiment of an optoelectronic apparatus in accordance with embodiments of the present invention;

[0041] FIG. 4 shows schematically a cross-sectional view of a third exemplary embodiment of an optoelectronic apparatus in accordance with embodiments of the present invention;

[0042] FIG. 5 shows transmittance curves as a function of normalized relative power over wavelength for different incidence angles using a linear scale on the y-axis.

[0043] FIG. 6 shows the transmittance curves of FIG. 5 using a logarithmic scale on the y-axis; and

[0044] FIG. 7 shows an exemplary transmittance curve taking account of all incidence angles as a function of signal power in artificial units over wavelength in nanometer, and a curve showing the optical response of a stand-alone photodiode.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0045] The optoelectronic apparatus shown in FIGS. 1 and 2 comprises a light detector 11, such as a photodiode. The light detector 11 comprises a bottom side 13, an upper side 15 and at least one sidewall 17 that extends in a circumferential direction CD and between the upper side 15 and the bottom side 13.

[0046] The light detector 11 can be arranged in a housing. The housing can comprise the bottom side 13 and the sidewall 17, while at least a portion of the upper side 15 comprises an opening through which light can be incident on the light detector 11. Alternatively, the light detector 11 cannot have a housing. For example, the light detector 11 can be a chip, such as a photodiode chip, and the bottom side 13, the upper side 15 and the sidewall 17 can correspond to surfaces of the unhoused light detector 11.

[0047] The apparatus comprises a carrier 19, for example a lead frame, which has an upper surface 21. The light detector 11 is arranged on the carrier 19 such that the bottom side 13 of the light detector 11 rests on the upper surface 21 of the carrier 19.

[0048] A filter 23 is arranged on the upper side 15 such that it covers at least partially the upper side 15 of the light detector 11. For example, it covers a central portion of the upper side 15, but it does not cover a contact pad to which a bond wire 25 is connected. The bond wire 25 electrically connects the contact pad to an electric conductor 39 of the carrier 19.

[0049] The filter 23 can in particular be arranged to cover a light detection window (not shown) which is located on the upper side 15 and which serves as a detection area for incident light.

[0050] Furthermore, a first material layer 27 covers the filter 23, and the upper side 15 of the light detector 11.

[0051] As shown in FIGS. 1 and 2, the apparatus can comprise at least one outer wall 29, which is arranged on the upper surface 21 of the carrier 19 and which extends in a circumferential direction CD around the sidewall 17 of the light detector 11. In the shown example, the outer wall 29 has a cross-sectional shape of a square or rectangular ring.

[0052] The carrier 19 and the outer wall 29 form a cavity in which the light detector 11 resides and which has an opening 31 on the top. As shown in FIG. 1 the upper surface 21 of the carrier 19 forms the bottom of this cavity, and the first material layer 27 closes the opening 31 and extends over the entire length and width of the opening 31.

[0053] A second material layer 33 is arranged below the first material layer 27, in a volume 35 that is located between the first material layer 27, the carrier layer 19, the sidewall 17 of the light detector 11, and the outer wall 29. The second material layer 33 covers the sidewall 17 of the light detector 11. In some embodiments, the second material layer 33 covers completely the sidewall 17. The height of the second material layer 33 can then correspond to the height of the sidewall 17 of the light detector 11. Alternatively, as shown in FIG. 1, in some embodiments the first material layer 33 can cover a small top portion of the sidewall 17, while the second material layer 33 covers the major portion of the sidewall 17.

[0054] Some applications require the use of photodetectors, which are highly selective in one or more spectral bands. For example, in some applications, it is desirable to be able to detect light at a wavelength which is equal to or larger than a cut-off wavelength, while light at wavelengths shorter than the cut-off may disturb the detection and negatively affect the signal-to-noise ratio, so that its detection is undesirable.

[0055] The filter 23 is configured to have a first threshold wavelength which lies between a first wavelength region and an adjacent second wavelength region. Thus, the first threshold wavelength separates the first wavelength region from the second wavelength region. The filter can have a lower transmittance for light at wavelengths in the first wavelength region than for light at wavelengths in the second wavelength region.

[0056] In some embodiments, the filter 23 is a longpass filter and the first threshold wavelength corresponds to a cut-on wavelength at which the transmission increases to 50% throughput. The transmission in the first wavelength regions is lower than 50%, and the first wavelength region includes wavelengths that are lower than the first threshold wavelength. The transmission of the filter in the second wavelength region is higher than 50%, and the second wavelength region corresponds to wavelengths above the first threshold wavelength.

[0057] In some embodiments, the transmission function of the filter 23 in the wavelength region around the first threshold wavelength can have a high slope. The term slope can be used to specify the bandwidth in wavelength over which the filter transitions from high blocking to high transmission. For example, given as the percent of the cut-on wavelength, the slope can be defined from a variety of starting and end points. The slope might be specified as the distance from the 10% transmission point to the 90% transmission point. Using this definition, for example a 500 nm longpass filter with a 1% slope would be expected to transition from 10% transmission to 90% transmission over a 5 nm bandwidth, where the 5 nm corresponds to 1% of 500 nm.

[0058] In some embodiments, the filter 23 is a longpass filter and has a 5%, 2.5%, or 1% slope with regard to a predetermined first threshold wavelength.

[0059] The first material layer 27 is configured to have a higher absorbance for light at wavelengths in a third wavelength region than for light at wavelengths in an adjacent fourth wavelength region. A second threshold wavelength separates the third and fourth wavelength regions. The first threshold wavelength of the filter 23 at least approximately corresponds to the second threshold wavelength. Thus, the first threshold wavelength of the filter 23 and the second threshold wavelength of the first material layer 27 at least approximately match with each other.

[0060] Moreover, at least in some embodiments, the third wavelength region can correspond to the first wavelength region of the filter 23, and the fourth wavelength region can correspond to the second wavelength region of the filter 23. In the embodiments in which the filter 23 corresponds to a longpass filter, the first material layer 27 therefore can act as absorber for light at wavelengths in the third wavelength region. Such light, if not absorbed, is blocked by the filter 23. Moreover, the first material layer 27 absorbs far less light at wavelengths in the fourth wavelength region. Thus, the light for which the longpass filter 23 has a high transmittance is also not absorbed or at a far lower rate by the first material layer 27. The first material layer 27 may therefore help to improve the filtering functionality of the filter 23.

[0061] The filter 23, for example in form of a longpass filter, can be a dielectric filter that comprises multiple thin layers of dielectric and, optionally, metallic material having different refractive indices. The dielectric filter can have a thickness of around 10 μm. Alternatively, the longpass filter can be made of a resist material. The resist material can have a thickness of around 1 μm.

[0062] The properties of the filter 23 can be dependent on the angle of incidence of the light. As will be outlined further below with regard to FIGS. 5 to 7, the use of the first material layer 27 in combination with the filter 23 can be advantageous, as the first material layer 27 can compensate the dependency on the angle of incidence and thus improve the overall filtering properties.

[0063] The first material layer 27 can be made in form of a cast, using for example epoxy and/or silicone, which includes absorber materials, for example in form of particles. The absorber materials can be configured to provide the described properties of a higher absorbance in the third wavelength region than in the adjacent fourth wavelength region.

[0064] The first material layer 27 can for example have a thickness in the range of 200 μm to 300 μm.

[0065] The second material layer 33 is configured to absorb light at wavelengths below and above the first threshold wavelength in order to prevent light absorption at the sidewall 17 of the light detector 11, and/or to prevent light leakage through the package and/or the carrier 19. The second material layer 33 can be made in form of a cast, for example, comprising epoxy and/or silicone. Preferably, the cast comprises black filler material.

[0066] The second material layer 33 can have a thickness of for example 200 μm. In some embodiments, the thickness can be in a range of 200 μm to 300 μm. In some embodiments, the thickness is at least approximately equal to the thickness of the light detector 11.

[0067] The outer wall 29 is preferably blackened or darkened. The outer wall 29 therefore can also act as absorber.

[0068] In some embodiments, a clear resin (not shown) can be used between the light detector 11 and the filter 23 and the casting filter formed by the first material layer 27. The clear resin can have for example a thickness of 50 μm and can be transparent to the radiation both in the pass and stop bands of the filter 23 and the filter provided by the first material layer 27. Its function can be to avoid that the casting and filters lose their functionality when they are in touch with each other. The clear resin can act in this case as a sort of decoupling layer.

[0069] The apparatus as shown in FIG. 3 differs from the apparatus of FIGS. 1 and 2 in that the filter 23 consists of a third material layer 37 that also replaces the second material layer 33 that is not present in the embodiment of FIG. 3. The third material layer 37 can fully embed the light detector 11, and the thickness of the third material layer 37 is higher than the thickness of the light detector 11. For example, the thickness of the third material layer 37 can be 200 μm or more.

[0070] The apparatus as shown in FIG. 4 differs from the apparatus of FIGS. 1 and 2 in that it comprises an additional fourth material layer 41, for example of a thickness in the range of 1 to 100 μm. The fourth material layer 41 can be configured to have a higher absorbance for light at wavelengths in a fifth wavelength region than for light at wavelengths in an adjacent sixth wavelength region. A third threshold wavelength separates the fifth and sixth wavelength regions. The first threshold wavelength of the filter 23 can at least approximately correspond to the third threshold wavelength, and the fifth wavelength region can correspond to the first wavelength region, while the sixth wavelength region can correspond to the second wavelength region.

[0071] The fourth material layer 41 can be made from a resist material, and it can include absorber material particles that can be configured to provide the described properties of a higher absorbance in the fifth wavelength region than in the adjacent sixth wavelength region.

[0072] Each of the exemplary apparatuses as shown in FIGS. 1 to 4 comprises the filter 23 and the first material layer 27 that serve to detect light in the second wavelength region. The detection is in substance independent from the angle of incidence. Furthermore, the filter 23 and the first material layer 27 serve to avoid the detection of light in the first wavelength region. In addition, the darkened or blackened outer wall 29 as well as the absorbing second material layer 33 (for the embodiments of FIGS. 1, 2 and 4) serve to avoid detecting unwanted light, crosstalk and leakage of light into the apparatus.

[0073] FIG. 5 shows for the embodiment of FIGS. 1 and 2 calculated combined transmittance curves as a function of normalized relative power over wavelength for incidence angles of 0, 10°, 20°, 30°, 40°, 50°, and 60° using a linear scale on the y-axis. FIG. 6 shows the transmittance curves of FIG. 5 using a logarithmic scale on the y-axis. The incidence angles are measured with respect to a surface normal on the top surface 43 of the filter 23. The combined transmittance curves take the filtering properties of the filter 23 and the first material layer 27 into account.

[0074] FIGS. 5 and 6 show that the transmittance is low for wavelengths lower than the first threshold wavelength, here corresponding to the cut-on wavelength λ.sub.C≈750 nm, but in substance independent of the angle of incidence. The wavelength region with wavelengths lower than λ.sub.C correspond to the first and third wavelength regions. Furthermore, FIGS. 5 and 6 show that the transmittance is high for wavelengths higher than λ.sub.C. The small dependency on the angle of incidence is acceptable.

[0075] FIG. 7 shows for the embodiment of FIGS. 1 and 2 a calculated detection signal 51 as a function of signal power in artificial units over wavelength. The signal 51 takes account of all incident angles. FIG. 7 additionally shows a reference signal 53 of a stand-alone photodiode on which a corresponding filter 23 is deposited. FIG. 7 indicates that the detection signal 51 is up to a few orders of magnitude lower than the reference signal 53 for wavelengths below the cut-on wavelength λ.sub.C. Furthermore, the detection signal 51 is at least approximately equal to the reference signal 53 for wavelengths above the cut-on wavelength λ.sub.C.