Abstract
An optoelectronic semiconductor component is specified, including at least one layer stack having - an active zone for generating electromagnetic radiation, - at least one aluminum-containing current constriction layer including a first region and a second region, the second region having a lower electrical conductivity than the first region, and - a side surface which laterally delimits the layer stack and at which the second region is arranged, the second region being an oxidized region. A method for producing an optoelectronic semiconductor component is furthermore specified.
Claims
1. An optoelectronic semiconductor component comprising at least one layer stack comprising: an active zone for generating electromagnetic radiation, at least two aluminum-containing current constriction layers each comprising a first region and a second region, the second region having a lower electrical conductivity than the first region, and a side surface which laterally delimits the layer stack and at which the second region is arranged in each case, the second region being an oxidized region in each case, and wherein the current constriction layers differ from each other in their vertical extent and lateral extent of the second regions, the thicker current constriction layer having a greater lateral extent of the second region than the thinner current constriction layer.
2. The optoelectronic semiconductor component according to claim 1, wherein at least one of the first regions includes AlxGayIn1-x-yAsP and wherein 0.9 ≤ x ≤ 1 and x + y ≤ 1.
3. The optoelectronic semiconductor component according to claim 1, wherein the second region has a higher oxygen content than the first region in each case.
4. The optoelectronic semiconductor component according to claim 1, wherein at least one of the second regions has a lateral extent between 0.1 .Math.m and 100 .Math.m inclusive.
5. The optoelectronic semiconductor component according to claim 1, wherein at least one of the current constriction layers has a vertical extent between 2 nm and 200 nm inclusive.
6. The optoelectronic semiconductor component according to claim 1, wherein the at least one layer stack has a first main surface and a second main surface each arranged transversely to the side surface, at least one of the current constriction layers being arranged closer to the active region than to the first and/or second main surface.
7. The optoelectronic semiconductor component according to claim 1, wherein at least two of the aluminum-containing current constriction layers differ from each other in their material composition and/or vertical extent and/or lateral extent of the second regions.
8. The optoelectronic semiconductor component according to claim 1, comprising at least two layer stacks arranged one above the other, a tunnel junction being arranged between the layer stacks.
9. The optoelectronic semiconductor component according to claim 1, wherein the optoelectronic semiconductor component is an edge-emitting laser component and the side surface is provided for coupling out the electromagnetic radiation.
10. The optoelectronic semiconductor component according to claim 1, wherein at least one of the current constriction layers is arranged in the region of at least one of the following elements of the optoelectronic semiconductor component: p-contact layer, p-cladding layer, p-waveguide, active zone, n-contact layer, n-cladding layer, n-waveguide, buffer layer, nucleation layer, tunnel junction.
11. A method for producing an optoelectronic semiconductor component according to claim 1, comprising: providing at least one layer stack comprising at least two aluminum-containing starting layers and a side surface laterally delimiting the layer stack, and forming at least two current constriction layers each comprising a first region and each comprising a second region which is arranged at the side surface and has a lower electrical conductivity than the first region by oxidizing each of the at least two aluminum-containing starting layers in the second region, wherein the current constriction layers differ from each other in their vertical extent and lateral extent of the second regions, the thicker current constriction layer having a greater lateral extent of the second region than the thinner current constriction layer.
12. The method according to claim 11, wherein the second region is generated in each case by means of lateral oxidation of the starting layer starting from the side surface.
13. The method according to claim 12, wherein a penetration depth of the oxidation is regulated in each case by a vertical extent of the starting layer.
14. The method according to claim 12, wherein a penetration depth of the oxidation is regulated in each case by the aluminum content of the starting layer.
15. The method according to claim 12, wherein a penetration depth of the oxidation is regulated in each case by a duration of the oxidation process.
16. The optoelectronic semiconductor component according to claim 1, wherein the current constriction layers are arranged on different sides of the active zone.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] In the figures:
[0038] FIGS. 1A and 1C each show a schematic cross-sectional view of a right edge region of an optoelectronic semiconductor component according to a first and a second exemplary embodiment, wherein the current constriction layer is arranged in the region of a waveguide, and FIGS. 1A and 1B show a method for producing an optoelectronic semiconductor component according to the first exemplary embodiment,
[0039] FIGS. 2A and 2B each show a schematic cross-sectional view of a right edge region of an optoelectronic semiconductor component according to a third and a fourth exemplary embodiment, wherein the current constriction layer is arranged in the region of a cladding layer,
[0040] FIGS. 3A and 3B each show a schematic cross-sectional view of a right edge region of an optoelectronic semiconductor component according to a fifth and a sixth exemplary embodiment, wherein the current constriction layer is arranged in the region of the active zone,
[0041] FIG. 4 shows a schematic cross-sectional view of a right edge region of an optoelectronic semiconductor component according to a seventh exemplary embodiment, wherein the current constriction layer is arranged in the region of a contact layer,
[0042] FIG. 5 shows a schematic cross-sectional view of a right edge region of an optoelectronic semiconductor component according to an eighth exemplary embodiment, wherein the current constriction layer is arranged in the region of a buffer layer,
[0043] FIG. 6 shows a schematic cross-sectional view of a right edge region of an optoelectronic semiconductor component according to a ninth exemplary embodiment, which has current constriction layers in the region of the waveguides,
[0044] FIG. 7 shows a schematic cross-sectional view of a right edge region of an optoelectronic semiconductor component according to a tenth exemplary embodiment, which has current constriction layers in the region of the cladding layers,
[0045] FIG. 8 shows a schematic cross-sectional view of a right edge region of an optoelectronic semiconductor component according to an eleventh exemplary embodiment, which has current constriction layers in the region of the active zone,
[0046] FIG. 9 shows a schematic cross-sectional view of a right edge region of an optoelectronic semiconductor component according to a twelfth exemplary embodiment, which has current constriction layers in the region of the contact layer and the buffer layer,
[0047] FIG. 10 shows a schematic cross-sectional view of a right edge region of an optoelectronic semiconductor component according to a thirteenth exemplary embodiment, which has current constriction layers comprising second regions of different vertical and lateral extents,
[0048] FIG. 11 shows a schematic cross-sectional view of a right edge region of an optoelectronic semiconductor component according to a fourteenth exemplary embodiment, which has current constriction layers of different material compositions and oxidation depths,
[0049] FIG. 12 shows a schematic cross-sectional view of an optoelectronic semiconductor component according to a fifteenth exemplary embodiment, which has adjacent current constriction layers comprising second regions of different lateral extents,
[0050] FIG. 13 shows a schematic cross-sectional view of an optoelectronic semiconductor component according to a sixteenth exemplary embodiment, which has current constriction layers in the region of a tunnel junction.
DETAILED DESCRIPTION
[0051] In the exemplary embodiments and figures, identical elements, elements of the same kind or elements having the same effect may each be provided with the same reference signs. The elements shown and their proportions to one another are not necessarily to be regarded as true to scale; rather, individual elements may be shown exaggeratedly large for better representability and/or better understanding.
[0052] FIG. 1A shows a first exemplary embodiment of an optoelectronic semiconductor component 1 in a cross-sectional view, wherein a cross-sectional plane is arranged perpendicular to a side surface 2A and a first main surface 2B and second main surface 2C of a layer stack 2 of the semiconductor component 1. In particular, the optoelectronic semiconductor component 1 is an edge-emitting laser component in which electromagnetic radiation is coupled out of the optoelectronic semiconductor component 1 through the side surface 2A in a lateral direction L.
[0053] The optoelectronic semiconductor component 1 includes the layer stack 2 and a substrate 3 on which the layer stack 2 is arranged. The substrate 3 may be a growth substrate on which the layer stack 2 is epitaxially grown or a replacement substrate which replaces the original growth substrate.
[0054] The layer stack 2 comprises a plurality of n-side, at least partially n-conductive layers 13, 11, 12 and a plurality of p-side, at least partially p-conductive layers 9, 8, 7, which follow each other in the vertical direction V. Furthermore, the layer stack 2 has an active zone 4 arranged between the n-side layers 11, 12, 13 and the p-side layers 7, 8, 9. In particular, layer 7 is a p-contact layer, layer 8 is a p-cladding layer, layer 9 is a p-waveguide, layer 12 is an n-waveguide, layer 11 is an n-cladding layer, and layer 13 is a buffer layer. The layer stack 2 may have further layers (not shown) between the aforementioned layers 7, 8, 9, 11, 12, 13.
[0055] Furthermore, the active zone 4 can contain a sequence of individual layers by means of which a quantum well structure, in particular a single quantum well (SQW) or multiple quantum well (MQW) structure, is formed.
[0056] Furthermore, both the p-waveguide 9 and the n-waveguide 12 may each have a sequence of individual layers preferably with alternating refractive indices.
[0057] For the layer stack 2 or the semiconductor layers 4, 7, 8, 9, 11, 12, 13 contained therein, materials based on phosphide and/or arsenide compound semiconductors, which have been described in more detail above, are preferably considered.
[0058] Further, the layer stack 2 comprises an aluminum-containing current constriction layer 5 comprising a first region 5A and a second region 5B, wherein the second region 5B has a lower electrical conductivity than the first region 5A and is an oxidized region.
[0059] The oxidized region 5B is generated by oxidation O of an originally non-oxidized aluminum-containing current constriction layer or starting layer 50 (cf. FIG. 1B). By oxidation O of the starting layer 50, i.e. by increasing the oxygen content, in the second region 5B, the electrical conductivity in the second region 5B is reduced. By means of the current constriction layer 5, a current in the semiconductor component 1 can thus be laterally constricted to the first region 5A.
[0060] The starting layer 50 is advantageously a high-aluminum AlGaInAsP layer with an aluminum content of at least 90%. Preferred values are 90%, 95%, 98%, 99% and 100%. In other words, the starting layer is formed of AlxGayIn1-x-yAsP, where 0.9 ≤ x ≤ 1 and x + y ≤ 1. Furthermore, the first region 5A is a non-oxidized region of the starting layer 50, so that its material composition corresponds in particular to that of the starting layer. Accordingly, the first region 5A preferably contains or consists of AlxGayIn1-x-yAsP, where 0.9 ≤ x ≤ 1 and x + y ≤ 1.
[0061] The second, oxidized region 5B is arranged at the side surface 2A and can thus reduce a current flow directed toward the side surface 2A. This protects the side surface 2A, which is in particular a mirror facet, from excessive heating and degradation and enables an increase of the optical output power, since this is often limited by the degradation of the mirror facet.
[0062] In the first exemplary embodiment, the current constriction layer 5 is arranged in the p-waveguide 9. The current constriction layer 5 is thus arranged so close to the active zone 4 that hardly any expansion of the laterally constricted current can occur in an intermediate region between the current constriction layer 5 and the active zone 4.
[0063] The second region 5B has a lateral extent b between 0.1 .Math.m and 100 .Math.m inclusive, with preferred values being 0.1 .Math.m, 1 .Math.m, 5 .Math.m, 10 .Math.m, 15 .Math.m, 20 .Math.m, 25 .Math.m, 50 .Math.m, and 100 .Math.m.
[0064] Furthermore, the current constriction layer 5 may have a vertical extent d between 2 nm and 200 nm inclusive, with preferred values being 2 nm, 5 nm, 10 nm, 20 nm, 35 nm, 50 nm, 100 nm, 200 nm.
[0065] Referring to FIGS. 1A and 1B, a method for producing the optoelectronic semiconductor component 1 is explained in more detail. First, a layer stack 2 is provided having an aluminum-containing starting layer 50 and a side surface 2A laterally delimiting the layer stack 2. Then, a current constriction layer 5 having a first region 5A and a second region 5B arranged at the side surface 2A and having a lower electrical conductivity than the first region 5A is formed by oxidizing the aluminum-containing starting layer 50 in the second region 5B.
[0066] In particular, the oxidized region 5B is generated by means of lateral oxidation O of the starting layer 50 starting from the side surface 2A.
[0067] FIG. 1C shows a second exemplary embodiment of an optoelectronic semiconductor component 1. While the current constriction layer 5 is arranged on the p-side in the first exemplary embodiment, it is located on the n-side of the layer stack 2 in the n-waveguide 12 in the second exemplary embodiment. Compared to previous structures in which the current to the mirror facet can only be constricted on a side of the active zone of the laser diode facing away from the substrate, in the second exemplary embodiment the current constriction takes place on the n-side facing the substrate 3.
[0068] FIG. 2A shows a third exemplary embodiment of an optoelectronic semiconductor component 1. While the current constriction layer 5 is arranged in the p-waveguide 9 in the first exemplary embodiment, it is located in the p-cladding layer 8 in the third exemplary embodiment. Thus, the current constriction layer 5 is arranged further away from the active zone 4, so that additional strains caused by the current constriction layer 5 can be reduced.
[0069] FIG. 2B shows a fourth exemplary embodiment of an optoelectronic semiconductor component 1, in which the current constriction layer 5 is arranged in the n-cladding layer 11 and thus on the side of the layer stack 2 facing the substrate.
[0070] FIGS. 3A and 3B show a fifth and a sixth exemplary embodiment of an optoelectronic semiconductor component 1, wherein the current constriction layer 5 is arranged in the region of the active zone 4 on the side of the active zone 4 facing away from the substrate (cf. FIG. 3A) or on the side facing the substrate (cf. FIG. 3B). This allows the charge carrier density in the active zone 4 to be reduced in a targeted manner on the side surface 2A.
[0071] FIG. 4 shows a seventh exemplary embodiment of an optoelectronic semiconductor component 1. Here, the current constriction layer 5 is located in the region of the p-contact layer 7. Thus, the current constriction layer 5 is arranged even further away from the active zone 4 than in the third exemplary embodiment, so that additional strains caused by the current constriction layer 5 can be further reduced. In order to nevertheless ensure sufficient current constriction in the region of the active zone 4, the second region 5B can, for example, be formed with a larger lateral extent b than in the first exemplary embodiment.
[0072] FIG. 5 shows an eighth exemplary embodiment of an optoelectronic semiconductor component 1, in which the current constriction layer 5 is arranged in the region of the buffer layer 13 and thus on the side of the layer stack 2 facing the substrate. The current constriction layer 5 is arranged further away from the active zone 4 than in the fourth exemplary embodiment, so that additional strains caused by the current constriction layer 5 can be further reduced.
[0073] In the exemplary embodiments shown in FIGS. 6 to 9, the layer stacks 2 of the semiconductor components 1 each have a plurality of current constriction layers 5 arranged on the p-side and the n-side, so that current constriction can take place on both sides.
[0074] For example, in the ninth exemplary embodiment shown in FIG. 6, the current constriction layers 5 are arranged in the region of the p-waveguide 9 and the n-waveguide 12. This exemplary embodiment also has the advantages mentioned in connection with the first and second exemplary embodiments.
[0075] Furthermore, in the tenth exemplary embodiment shown in FIG. 7, the current constriction layers 5 are arranged in the region of the p-cladding layer 8 and the n-cladding layer 11. This exemplary embodiment also has the advantages mentioned in connection with the third and fourth exemplary embodiments.
[0076] In the eleventh exemplary embodiment shown in FIG. 8, the current constriction layers 5 are arranged in the region of the active zone 4. This exemplary embodiment also has the advantages mentioned in connection with the fifth and sixth exemplary embodiments.
[0077] Furthermore, in the twelfth exemplary embodiment shown in FIG. 9, the current constriction layers 5 are arranged in the region of the contact layer 7 and the buffer layer 13. This exemplary embodiment also has the advantages mentioned in connection with the seventh and eighth exemplary embodiments.
[0078] While the current constriction layers 5 in the exemplary embodiments shown in FIGS. 6 to 9 are formed in particular identically in each case, FIGS. 10 and 11 show exemplary embodiments in which the layer stack 2 has two current constriction layers 5 which differ from each other in the lateral extent b of the second regions 5B. This can be achieved in the thirteenth exemplary embodiment shown in FIG. 10 by different vertical extents d of the associated starting layers, with faster and thus laterally deeper penetrating oxidation occurring in the thicker starting layer than in the thinner starting layer.
[0079] In the fourteenth exemplary embodiment shown in FIG. 11, the current constriction layers 5 or the starting layers used to produce the current constriction layers 5 differ in their material composition. In this case, the material compositions are selected such that a faster and thus laterally deeper penetrating oxidation occurs in one starting layer than in the other starting layer. In particular, the starting layer in which faster oxidation occurs has a higher aluminum content.
[0080] FIG. 12 shows a fifteenth exemplary embodiment of a semiconductor component 1, in which the layer stack 2 has two adjacent current constriction layers 5 whose second regions 5B have different lateral extents b. In this way, a desired current profile can be adjusted in a targeted manner. In this case, the current constriction layer 5, which is arranged further away from the active zone 4, has a second region 5B with a greater lateral extent b. Furthermore, the current constriction layer 5 located closer to the active zone 4 advantageously has a higher doping than the other current constriction layer 5. In particular, an excess current at the transition between the two second regions 5B of the current constriction layers 5 can be mitigated in this way.
[0081] FIG. 13 shows a sixteenth exemplary embodiment of a semiconductor component 1, which has two layer stacks 2 of the above-mentioned type, which are arranged one above the other and in particular are monolithically integrated, a tunnel junction 6 being arranged between the layer stacks 2. The tunnel junction 6 comprises in particular two highly doped layers of different conductivity types (n-type and p-type, respectively) and serves to electrically connect the layer stacks 2. In the region of the tunnel junction 6, the semiconductor component 1 has two current constriction layers 5, which are arranged on opposite sides of the tunnel junction 6. Furthermore, the semiconductor component 1 has a current constriction layer 5 arranged in the cladding layer 8. By means of the layer stacks 2 arranged one above the other, a higher optical output power can be obtained, and the side surface 2A is advantageously protected from excessive heating and degradation by the current constriction layers 5.
[0082] In particular, the semiconductor components 1 described in connection with FIGS. 1C to 13 have a structure of the layer stack corresponding to the first exemplary embodiment except for the aforementioned differences.
[0083] The invention is not limited by the description based on the exemplary embodiments. Rather, the invention encompasses any new feature as well as any combination of features, which in particular includes any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or embodiments.
