Semiconductor layer sequence and optoelectronic semiconductor chip

Abstract

Semiconductor layer sequence (2) based on AlInGaN for an optoelectronic semiconductor chip (1) with the following layers in the specified order from an n-side (20): - a pre-barrier layer (21) made of AlGaN, - a pre-quantum well (23) made of InGaN with a first band gap, - a multi-quantum well structure (3) with several alternating principal quantum wells (32) made of InGaN with a second band gap and principal barrier layers (31) made of AlGaN or AlInGaN, wherein the second band gap is smaller than the first band gap and the principal quantum wells (32) are configured to generate radiation with a wavelength of maximum intensity between and including 365 nm and 490 nm, - a post-quantum well (26) with a third band gap that is larger than the second band gap, - a neighboring layer (27) of AlGaN or AlInGaN, and - an electron blocking layer (29) made of AlGaN, wherein a product of an aluminium content and thickness of the pre-barrier layer (21) and also a product of an aluminium content and thickness of the adjacent barrier layer (27) is each at least a factor of 1.3 larger than a product of an aluminium content and thickness of the main barrier layers (31).

Description

[0001] A semiconductor layer sequence is specified. Furthermore, an optoelectronic semiconductor chip is specified.

[0002] From publication KR 10 2016 0 013 552 A, a semiconductor layer sequence for an LED is known which includes an active region with several quantum wells.

[0003] From publication WO 2016 / 002 419 A1, a semiconductor layer sequence with an active region comprising several quantum wells and barrier layers is known.

[0004] One task is to specify a high-quality semiconductor layer sequence for generating short-wavelength radiation. Another task is to specify an optoelectronic semiconductor chip incorporating such a semiconductor layer sequence.

[0005] This problem is solved by a semiconductor layer sequence with the features of independent claim 1 and by an optoelectronic semiconductor chip with the features of claim 13. Preferred embodiments are the subject of the respective dependent claims.

[0006] The semiconductor layer sequence is based on AlInGaN. This means that the individual layers of the semiconductor layer sequence are made of Al x In y Ga 1-x-yN, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, and 0 ≤ x + y < 1. Dopants such as silicon or magnesium may also be present. For the sake of simplicity, however, only the essential components of the crystal lattice of the semiconductor layer sequence, namely Al, In, Ga, and N, are listed, even if these may be replaced by small amounts of other elements. In particular, impurities or admixtures are not considered below if they constitute a proportion of AlInGaN of at most 0.1 wt%.

[0007] The semiconductor layer sequence includes a pre-barrier layer. The pre-barrier layer is made of AlGaN. The aluminum content of the pre-barrier layer is preferably at least 2% or 20% and / or at most 50%, 40%, or 30%. In particular, the aluminum content is between 20% and 30% inclusive. The pre-barrier layer is preferably free of indium. In this context, the percentage values ​​for the indices x and y are in Al.x In y Ga 1-x-y N. An aluminum content of, for example, 30% means that x = 0.30, the same applies to y for the indium content.

[0008] Optionally, the pre-barrier layer can contain small amounts of indium and thus consist of Al. x In y Ga 1-x-y N is. In this case, the values ​​mentioned above for aluminum apply equally to an AlGaN pre-barrier layer. The indium content is preferably at most 1%, 0.5%, or 0.2%.

[0009] According to at least one embodiment, the pre-barrier layer has a thickness of at least 1 nm or 2.5 nm and / or at most 4 nm or 10 nm. In particular, the thickness of the pre-barrier layer is between 2.5 nm and 3.5 nm inclusive.

[0010] The semiconductor layer sequence includes a prequantum well. The prequantum well is made of InGaN. The prequantum well has a first band gap to which a first emission energy can be assigned. It is possible that the prequantum well is not configured for radiation generation in the intended use of the semiconductor layer sequence. That is, in this case, no radiation or no significant radiation is generated in the prequantum well during the intended use of the semiconductor layer sequence, and the prequantum well can be referred to as a dark quantum well. Alternatively, it is possible that the prequantum well contributes to radiation generation, for example, at a different wavelength than the principal quantum wells.

[0011] According to at least one embodiment, the prequantum pot has an indium content of at least 0.2%, 1%, or 2%, or alternatively, is free of indium. Alternatively or additionally, the indium content of the prequantum pot is at most 6% or 15%. In particular, the indium content is between 4% and 5.5% inclusive. The prequantum pot is particularly preferably free of aluminum.

[0012] According to at least one embodiment, the forequantum well has a thickness of at least 1.5 nm or 2.2 nm and / or at most 5 nm or 3.4 nm. In particular, the thickness of the forequantum well is between 2.4 nm and 2.8 nm inclusive.

[0013] The semiconductor layer sequence comprises a multi-quantum well structure. This structure includes several alternating principal quantum wells and principal barrier layers. The principal quantum wells are made of InGaN, and the principal barrier layers are made of AlGaN or AlInGaN. The principal quantum wells have a second band gap corresponding to a second emission energy that is greater than or equal to the first band gap of the pre-quantum well. The principal quantum wells are configured to generate radiation with a wavelength of maximum intensity of at least 365 nm, 375 nm, or 385 nm and / or at most 490 nm, 410 nm, or 395 nm.

[0014] According to at least one embodiment, the indium content of the principal quantum wells is at least 0.2%, 2%, or 4%, or alternatively, the principal quantum wells are free of indium. Alternatively or additionally, the indium content of the principal quantum wells is at most 5% or 15%. In particular, the indium content of the principal quantum wells is between 5% and 6.5% inclusive. The principal quantum wells are particularly preferably free of aluminum.

[0015] According to at least one embodiment, the principal quantum wells have a thickness of at least 1.5 nm or 2.2 nm and / or at most 5 nm or 3.4 nm. In particular, the thickness of the principal quantum wells is between 2.4 nm and 2.8 nm inclusive.

[0016] According to at least one embodiment, the main barrier layers have an aluminum content of at least 2% or 10% and / or at most 20% or 30%. In particular, the aluminum content of the main barrier layers is between 12% and 18% inclusive. Preferably, the main barrier layers are free of indium, but may also have a small indium content of at most 1%, 0.5%, or 0.2%.

[0017] According to at least one embodiment, the main barrier layers have a thickness of at least 0.5 nm or 0.9 nm and / or at most 5 nm or 2.3 nm. In particular, the thickness of the main barrier layers is between 1.5 nm and 2 nm inclusive.

[0018] The semiconductor layer sequence includes an electron blocking layer. The electron blocking layer is formed from AlGaN and can be indium-free or contain a small amount of indium, for example, at most 0.5%, 1%, or 2%. The thickness of the electron blocking layer is preferably at least 6 nm, 8 nm, or 10 nm and / or at most 20 nm, 15 nm, or 12 nm. Furthermore, it is preferred that the aluminum content or average aluminum content of the electron blocking layer is at least 15%, 20%, or 30% and / or at most 80%, 70%, or 60%.

[0019] A product of the aluminum content and the thickness of the pre-barrier layer is at least 1.3 times greater than a product of the aluminum content and the thickness of the main barrier layers or the nearest main barrier layer. Preferably, this factor is at least 1.5, 2, 2.5, or 3. Furthermore, it is possible for this factor to be at most 7, 5, or 4.

[0020] The semiconductor layer sequence is based on AlInGaN and is intended for an optoelectronic semiconductor chip, in particular a light-emitting diode or a laser diode. The semiconductor layer sequence comprises the following layers in the specified order, viewed from an n-conducting n-side: - a pre-barrier layer made of AlGaN, - a pre-quantum well made of InGaN with a first band gap, - a multi-quantum well structure with several alternating principal quantum wells made of InGaN with a second band gap and principal barrier layers made of AlGaN or AlInGaN, wherein the second band gap is larger than or equal to the first band gap and the principal quantum wells are configured to generate radiation with a wavelength of maximum intensity between and including 365 nm and 490 nm, - an azimuthal quantum well with a third band gap that is larger than the second band gap, - a neighboring layer of AlGaN or AlInGaN, and - an electron-blocking layer made of AlGaN, wherein a product of an aluminium content and thickness of the pre-barrier layer and also a product of an aluminium content and thickness of the neighboring barrier layer is each at least a factor of 1.3 larger than a product of an aluminium content and thickness of the main barrier layers or the nearest main barrier layer.

[0021] The optoelectronic semiconductor chip comprises a semiconductor layer sequence according to one of the embodiments described herein and a substrate which is a growth substrate for the semiconductor layer sequence.

[0022] Specifically for UVA-spectral LEDs, an excessively high aluminum content combined with a reduced indium content in the optically active layers, particularly in the quantum films or quantum wells, leads to tensilely stressed layer stacks. This can, for example, cause cracking and thus quality problems, especially in substrate-free thin-film LEDs.

[0023] Furthermore, it is important to note that charge carrier transport and capture at the quantum wells must be controlled by adding aluminum to the barriers between the quantum wells. Excessively high aluminum concentrations negatively impact a homogeneous charge carrier distribution within the multi-quantum well structure. Conversely, if the aluminum content is too low, non-radiative losses increase, particularly at high current densities and temperatures, due to an insufficient charge carrier capture rate. In such cases, it is possible for both electrons and holes to escape the multi-quantum well structure and subsequently recombine non-radiatively in adjacent layers.

[0024] The semiconductor layer sequence described here comprises a combination of a pre-barrier layer and a pre-quantum well, and preferably also a neighboring rier layer and a post-quantum well. The pre-barrier layer, the neighboring rier layer, the pre-quantum well, and the post-quantum well are located in the immediate vicinity of the multi-quantum well structure. Due to the higher aluminum content and / or the greater thickness of the pre-barrier layer and / or the neighboring rier layer, the transition energies, corresponding to band gaps, of directly adjacent quantum wells would be energetically lower due to piezoelectric fields, leading to an uneven charge carrier distribution within the quantum wells.

[0025] Consequently, in the semiconductor layer sequence described here, the pre-quantum wells and post-quantum wells directly adjacent to the multi-quantum well structure and to the pre-barrier and neighboring rye layers have less indium and / or a smaller layer thickness. Alternatively, with a sufficiently large piezoelectric effect, they can also be thinner with a comparable indium content. Furthermore, the main barrier layers between the principal quantum wells have a smaller thickness and / or a lower aluminum content than the pre-barrier and neighboring rye layers.

[0026] According to at least one embodiment, the indium content and / or thickness of the prequantum well is smaller than the indium content and / or thickness of the principal quantum wells. For example, the indium content and / or thickness differ by at least 5% or 10% and / or by at most 40% or 25%, relative to the thickness and / or indium content of the principal quantum wells.

[0027] Moving away from the n-side, a post-quantum well follows the multi-quantum well structure. The post-quantum well has a third band gap that is smaller than the second band gap of the principal quantum wells. The post-quantum well can be designed identically to the pre-quantum well, such that the third band gap can be the same as the first band gap. Therefore, the above specifications regarding thickness, indium content, and aluminum content for the pre-quantum well apply equally to the post-quantum well. Alternatively, the pre-quantum well and the post-quantum well can have different designs.

[0028] In particular, the post-quantum well is free of aluminum and has an indium content of at least 0.2% or 1% and / or at most 6% or 15%, or is free of indium. Specifically, the indium content is between 4% and 5.5% inclusive. For example, the post-quantum well has a thickness of at least 1.5 nm or 2.2 nm and / or at most 5 nm or 3.4 nm. Specifically, the thickness of the pre-quantum well is between 2.4 nm and 2.8 nm inclusive.

[0029] A neighboring Rier layer follows the multi-quantum well structure in the direction away from the n-side. The neighboring Rier layer is made of AlGaN or AlInGaN. The neighboring Rier layer can be designed identically to the pre-barrier layer. The above-mentioned specifications regarding thickness, composition, and band gap for the pre-barrier layer preferably also apply to the neighboring Rier layer. Preferably, the neighboring Rier layer follows the post-quantum well such that the post-quantum well is located between the multi-quantum well structure and the neighboring Rier layer.

[0030] According to at least one embodiment, the electron-blocking layer follows the neighboring layer in the direction away from the n-side. The electron-blocking layer preferably has a thickness that is at least 1.5, 2, or 3 times greater and / or at most 10, 6, or 4 times greater than that of the neighboring layer. Preferably, the barrier height of the electron-blocking layer is also at least equal to, and particularly preferably at least 1.25, 1.5, or 2 times greater than that of the neighboring layer. In other words, the electron-blocking layer blocks electrons more effectively than the neighboring layer.

[0031] According to at least one embodiment, a spacer layer is located between the electron blocking layer and the neighboring layer. Preferably, the spacer layer is directly adjacent to the electron blocking layer and / or the neighboring layer. The spacer layer is made of GaN, InGaN, AlGaN, or AlInGaN. Preferably, the thickness of the spacer layer is at least 5 nm or 8 nm and / or at most 20 nm, 15 nm, or 12 nm. The aluminum content of the spacer layer is preferably at most 5%, 2%, or 0.5%, or the spacer layer is free of aluminum. The indium content of the spacer layer is preferably at most 5%, 2%, or 1% and / or at least 0.5% or 1%; alternatively, the spacer layer is free of indium.

[0032] According to at least one embodiment, the electron blocking layer is designed as a multi-layered structure. Alternatively, it is possible that the electron blocking layer is composed of several spaced-apart sublayers. The aluminum content or average aluminum content of the electron blocking layer is preferably at least 15%. It is possible that the aluminum content in the sublayers of the electron blocking layer, or for the electron blocking layer as a whole, decreases monotonically or strictly monotonically in the direction away from the n-side.

[0033] According to at least one embodiment, the aluminum content within the pre-barrier layer and / or the main barrier layers and / or the adjacent barrier layer is constant, particularly within the manufacturing tolerances. Alternatively or additionally, it is possible that the indium content in the pre-quantum well, the main quantum wells, and the post-quantum well is constant, again within the manufacturing tolerances.

[0034] According to at least one embodiment, a conditioning layer is located on one or both sides of the forequantum well. The thickness of the conditioning layer is preferably at least 0.1 nm or 1 nm and / or at most 5 nm or 2 nm, particularly between 1.6 nm and 2 nm inclusive. The conditioning layer is preferably based on GaN. Alternatively, the conditioning layer may contain small amounts of indium, for example, at most 2% or 1%, particularly between 0.1% and 0.3% inclusive. The conditioning layer may be free of aluminum.

[0035] Alternatively, the conditioning layer may contain aluminum. The aluminum content of the conditioning layer is preferably at most 100%, 50%, 20%, or 5% of the aluminum content of the nearest main barrier layer.

[0036] According to at least one embodiment, one or two conditioning layers are located directly at each principal quantum well. The conditioning layers at the principal quantum wells can be designed in the same way as the conditioning layers at the pre-quantum well and / or the post-quantum well. Alternatively, the conditioning layers at the pre-quantum well and / or the post-quantum well can be designed differently from the conditioning layers at the principal quantum wells.

[0037] According to at least one embodiment, the conditioning layers split each band gap jump between the main barrier layers and the adjacent prequantum well or the adjacent principal quantum well into two smaller jumps. Each of the two smaller jumps can be 50% of the larger, total band gap jump. Alternatively, one of the two jumps is at least 25%, 35%, or 40% and / or at most 45% or 40% of the total, larger band gap jump.

[0038] According to at least one embodiment, the conditioning layers, or a portion thereof, exhibit an indium gradient with an increasing indium content towards the adjacent prequantum well, principal quantum well, or postquantum well. Alternatively or additionally, an aluminum gradient is present with an increasing aluminum content away from the adjacent prequantum well, principal quantum well, or postquantum well. Such gradients enable improved crystal quality in the semiconductor layer sequence towards the quantum wells and / or improved electro-optical characteristics.

[0039] According to at least one embodiment, the semiconductor layer sequence comprises exactly one prequantum well and / or exactly one postquantum well. Alternatively, multiple prequantum wells and / or multiple postquantum wells are present. The number of prequantum wells and / or postquantum wells is preferably at most five or three, respectively.

[0040] According to at least one embodiment, the semiconductor layer sequence in the multi-quantum well structure has at least four, eight, or twelve and / or at most 50, 30, or 20 principal quantum wells. The number of principal quantum wells preferably exceeds the sum of the number of pre-quantum wells and post-quantum wells by at least a factor of 2, 4, or 8.

[0041] According to at least one embodiment, all pairs of principal barrier layers and principal quantum wells, as well as the optionally present conditioning layers, are identical in the multi-quantum well structure. Alternatively, it is possible for the principal barrier layers, the principal quantum wells, and optionally the conditioning layers to vary across the multi-quantum well structure.

[0042] According to at least one embodiment, the pre-barrier layer and optionally the adjacent barrier layer as well as the main barrier layers have the same aluminum content, in particular with a tolerance of at most 20%, 10%, or 2%, or within the manufacturing tolerances. In other words, only the thicknesses of the main barrier layers differ from the thicknesses of the pre-barrier layer and / or the adjacent barrier layer.

[0043] According to at least one embodiment, the second band gap of the principal quantum wells is at least 70%, 80%, or 85% and / or at most 95%, 90%, or 85% of the first band gap of the pre-quantum well and / or the post-quantum well. Preferably, within the manufacturing tolerances, all principal quantum wells have the same band gap.

[0044] The following section provides a more detailed explanation of a semiconductor layer sequence described here, with reference to the drawing and illustrated by exemplary embodiments. Identical reference symbols indicate identical elements in the individual figures. However, the figures are not to scale; rather, individual elements may be exaggerated for clarity.

[0045] They show: Fig. 1 A schematic representation of a semiconductor layer sequence described here, based on the course of a band gap, Fig. 2 a schematic sectional view of an embodiment of a semiconductor chip with a semiconductor layer sequence described herein, and Fig. 3 schematic representations of the dependence of brightness on a thickness ratio of the main barrier layers and the pre-barrier layer of semiconductor layer sequences described here.

[0046] In Fig. Figure 1 schematically illustrates an embodiment of a semiconductor layer sequence 2 by depicting the path of a band gap along a growth direction G. The growth direction G runs from an n-type n-side 20 to a p-type p-side 40.

[0047] Optionally, the semiconductor layer sequence 2 has a superlattice with alternating layers in front of a pre-barrier layer 21. Along the growth direction G, further layers such as buffer layers, nucleation layers, or growth layers can precede the superlattice, these layers being represented in the following for the sake of simplicity: Fig. 1 are not illustrated.

[0048] A pre-barrier layer 21 serves as a hole-blocking layer. The thickness of the pre-barrier layer 21 is, for example, 2.9 nm. The pre-barrier layer 21 is made of AlGaN with an aluminum content of 30%, i.e., Al. 0,3 Ga 0,7 N.

[0049] The pre-barrier layer 21 is followed by a conditioning layer 22. The conditioning layer 22 is a thin layer of InGaN with a low indium content of 0.2%. The thickness of the conditioning layer 22 is 1.8 nm.

[0050] The conditioning layer is followed by a prequantum well 23, which is not primarily intended for radiation generation. The prequantum well 23 is made of InGaN with an indium content of 5% and a thickness of 2.6 nm.

[0051] The prequantum well 23 is followed by a multiquantum well structure 3, which is intended for radiation generation, for example for the generation of near-ultraviolet radiation with a wavelength of maximum intensity between 390 nm and 395 nm inclusive. In the multiquantum well structure 3, principal barrier layers 31 and principal quantum wells 32 alternate.

[0052] Preferably, one of the conditioning layers 22 is located between adjacent principal barrier layers 31 and the associated principal quantum wells 32. All conditioning layers 22 can be identical to each other. The multi-quantum well structure 3, for example, comprises 20 of the principal quantum wells 32. Preferably, the multi-quantum well structure 3 begins and ends with one of the principal barrier layers 31.

[0053] The band gap or emission energy of the principal quantum wells 32 is smaller than or equal to the band gap or emission energy of the prequantum well 23.

[0054] The optionally available conditioning layers 22 can, as in Fig. As illustrated by a dashed line in Figure 1, each layer exhibits an indium gradient and / or an aluminum gradient, such that in the conditioning layers 22 the band energy profile is oriented obliquely to the growth direction G, thus enabling a more uniform transition of the band gap from the associated barrier layers 21, 31, 27 to the quantum wells 23, 32, 26. In particular, the conditioning layers 22 can be designed symmetrically with respect to the associated quantum wells 23, 32, 26.

[0055] The principal quantum wells 32 and the principal barrier layers 31 within the multiquantum well structure 3 are identical in design. For example, the principal quantum wells 32 made of InGaN have a thickness of 2.6 nm and an indium content of 6%. The AlGaN principal barrier layers 31 have a thickness of 1.7 nm and an aluminum content of 15%.

[0056] Immediately following the last main barrier layer 31 and the associated conditioning layer 22 is a post-quantum well 26. The post-quantum well 26 can be designed in the same way as the pre-quantum well 23 and, for example, have a thickness of 2.6 nm and an indium content of 5%. The conditioning layers 22 are also located on both sides of the post-quantum well 26.

[0057] The last of the conditioning layers 22 along the growth direction G, or all conditioning layers 22 following the associated quantum well 23, 32, 26, can optionally be thicker and / or have a higher indium content than the conditioning layers 22 preceding the associated quantum well 23, 32, 26 and, for example, have an indium content of at least 1% and / or at most 15% or 6%, or be free of indium and have a thickness of at least 1.5 nm or 2.2 nm and / or at most 3.4 nm or 5 nm.

[0058] A neighboring layer 27 is particularly favorably located directly after the last conditioning layer 22, which follows the post-quantum well 26 along the growth direction G. The neighboring layer 27 is a barrier layer for electrons with a relatively low barrier height compared to a subsequent electron-blocking layer 29. For example, the neighboring layer 27 is identical in design to the pre-barrier layer 21 or may also differ from the pre-barrier layer 21. Fig. 1 The AlGaN barrier layer 27 has an aluminum content of 15% and a thickness of 2.9 nm.

[0059] The neighboring layer 27 is directly followed by a spacer layer 28, which is made of InGaN and is preferably free of aluminum and has a low indium content of, for example, at most 1%. The thickness of the spacer layer 28 is 10 nm.

[0060] The two-stage electron blocking layer 29 directly follows the spacer layer 28. The total thickness of the electron blocking layer 29 is 11 nm. The average aluminum content in the electron blocking layer 29 is 25%, with the aluminum content decreasing in steps along the growth direction G.

[0061] The electron blocking layer 29 is preferably followed by a p-doped GaN layer and a contact layer, which may be made of highly doped GaN.

[0062] The in Fig. The layers shown in Figure 1 preferably follow one another directly. Preferably, all layers shown, with the exception of the conditioning layers 22 and / or the electron-blocking layer 29, have a constant material composition. All layers upstream of the multi-quantum well structure 3 along the growth direction 3 are preferably n-doped, and all downstream layers are preferably p-doped. The multi-quantum well structure 3 can be doped or undoped.

[0063] In the semiconductor layer sequence described here, the main barrier layers 31 can be made thinner, particularly due to the pre-barrier layer 21 and the optional neighboring layer 27, especially in combination with the pre-quantum well 23 and / or the post-quantum well 26. This results in higher transparency of the generated radiation in the region of the multi-quantum well structure 3. Significant advantages are also observed at higher current densities, as the charge carriers can be distributed more effectively across the main quantum wells 32. Nevertheless, the pre-barrier layer 21 and the neighboring layer 27 retain the charge carriers within the multi-quantum well structure 3 and prevent leakage currents. Since the charge carriers cannot escape significantly from the multi-quantum well structure via the pre-barrier layer 21 and / or the neighboring layer 27, even at higher ambient temperatures, improved temperature stability is achieved.This results in a highly efficient structure which can be adapted to the desired emission wavelength of the principal quantum wells 32 by the aluminium content and the thickness of the main barrier layers 31 and the pre-barrier layer 21 as well as the neighboring barrier layer 27.

[0064] In Fig. Figure 2 illustrates an embodiment of an optoelectronic semiconductor chip 1, which has such a semiconductor layer sequence 2. The semiconductor layer sequence 2 is located on a substrate 6, which can be a grow substrate. For example, the substrate 6 is a sapphire substrate with a structured grow surface. The semiconductor layer sequence 2 can be electrically contacted via electrical contacts 5. Preferably, the semiconductor layer sequence 2 extends over the entire substrate 6 with a consistent composition.

[0065] In Fig. Figure 3 illustrates a brightness L in arbitrary units as a function of a quotient Q. The quotient Q is given as a percentage and corresponds to the thickness of the main barrier layers 31 divided by the thickness of the pre-barrier layer 21. According to Fig. 3 the thickness of the pre-barrier layer 21 is fixed at 3 nm, the thickness of the main barrier layers 31 is varied.

[0066] In Fig. 3A represents a curve at a current of 1 A, in Fig. 3B with the dashed line a course at a current of 0.35 A and in the solid line in Fig. 3B for a current of 1.5 A, each with a chip area of ​​1 mm² 2 .

[0067] From the Fig. 3A and Fig. Figure 3B shows that an optimum is reached for a value of the quotient Q of 50% to 60%. That is, the pre-barrier layer 21 and preferably also the adjacent barrier layer 27 are approximately twice as thick as the main barrier layers 31. In particular, the thickness of the main barrier layers 31 is between 40% and 65% or between 45% and 60% of the thickness of the pre-barrier layer 21.

[0068] Furthermore, it is from the Fig. 3A and Fig. Figure 3B shows that the quotient Q exhibits a more pronounced decrease towards thicker main barrier layers 31 for higher currents. This means that improved efficiency can be achieved with the pre-barrier layers 21 and main barrier layers 31 described here, particularly at higher current densities. Reference symbol list 1 optoelectronic semiconductor chip 2 Semiconductor layer sequence 20 n-page 21 Pre-barrier layer 22 Conditioning layer 23 Pre-quantum pot 26 Post-quantum pot 27 Neighborhood layer 28 spacer layer 29 Electron blocking layer 3 Multi-quantum well structure 31 Main barrier layer 32 Principal quantum well 40-page 5 electrical contacts 6 Substrat G Growth direction of the semiconductor layer sequence L Brightness in arbitrary units (au) Q is the quotient of the thickness of the main barrier layers and the thickness of the upstream or neighboring barrier layer.

Claims

[1] Semiconductor layer sequence (2) based on AlInGaN for an optoelectronic semiconductor chip (1) with the following layers in the specified order from an n-side (20): - a pre-barrier layer (21) made of AlGaN, - a pre-quantum well (23) made of InGaN with a first band gap, - a multi-quantum well structure (3) with several alternating principal quantum wells (32) made of InGaN with a second band gap and principal barrier layers (31) made of AlGaN or AlInGaN, wherein the second band gap is smaller than the first band gap and the principal quantum wells (32) are configured to generate radiation with a wavelength of maximum intensity between and including 365 nm and 490 nm, - a post-quantum well (26) with a third band gap that is larger than the second band gap, - a neighboring layer (27) of AlGaN or AlInGaN, and - an electron blocking layer (29) made of AlGaN, wherein a product of an aluminium content and thickness of the pre-barrier layer (21) and also a product of an aluminium content and thickness of the adjacent barrier layer (27) is each at least a factor of 1.3 larger than a product of an aluminium content and thickness of the main barrier layers (31). [2] Semiconductor layer sequence (2) according to the preceding claim, where the wavelength of maximum intensity lies between 365 nm and 395 nm inclusive, wherein the product of the aluminium content and the thickness of the pre-barrier layer (21) is at most a factor of 5 greater than the product of the aluminium content and the thickness of the main barrier layers (31), wherein the prequantum well (23) is not configured for radiation generation, and wherein an indium content and / or thickness of the prequantum well (23) is smaller than an indium content and / or thickness of the principal quantum wells (32). [3] Semiconductor layer sequence (2) according to one of the preceding claims, wherein the aluminium content of the electron blocking layer (29) is at least 20% and the thickness of the electron blocking layer (29) is at least 8 nm and at most 15 nm. [4] Semiconductor layer sequence (2) according to one of the preceding claims, wherein the electron blocking layer (29) is multi-stage and the aluminium content of the electron blocking layer (29) decreases strictly monotonically in the direction away from the n-side (20). [5] Semiconductor layer sequence (2) according to any of the preceding claims, in which the electron blocking layer (29) follows the neighboring layer (27) in the direction away from the n-side (20) and a spacer layer (28) made of GaN or AlGaN or AlInGaN with a thickness between and including 5 nm and 15 nm and an aluminum content of at most 5% is located directly between the electron blocking layer (29) and the neighboring layer (27), wherein the electron blocking layer (29) represents a barrier to electrons that is at least 1.5 times thicker and / or higher than the neighboring layer (27). [6] Semiconductor layer sequence (2) according to one of the preceding claims, wherein the aluminium content within the pre-barrier layer (21), the main barrier layers (31) and the neighboring barrier layer (27) and the indium content in the pre-quantum well (23), the main quantum wells (32) and the post-quantum well (26) is constant. [7] Semiconductor layer sequence (2) according to any of the preceding claims, where a conditioning layer (22) is located directly on both sides of the prequantum well (23) and directly on both sides of the principal quantum wells (32), wherein the conditioning layers (22) are each between 1 nm and 2 nm thick inclusive, and wherein by the conditioning layers (22) each band gap jump between the main barrier layers (31) and the adjacent prequantum well (23) or principal quantum well (32) is divided into two smaller jumps. [8] Semiconductor layer sequence (2) according to the preceding claim, wherein the conditioning layers (22) have an indium gradient with an indium content increasing towards the adjacent prequantum well (23) or principal quantum well (32) and / or an aluminum gradient with an aluminum content increasing away from the adjacent prequantum well (23) or principal quantum well (32). [9] Semiconductor layer sequence (2) according to any of the preceding claims, where the main barrier layers (31) have a thickness between 0.9 nm and 2.3 nm inclusive and an aluminium content between 10% and 20% inclusive, wherein the exactly one pre-barrier layer (21) has a thickness between 2.5 nm and 4 nm inclusive and an aluminium content between 20% and 40% inclusive. [10] Semiconductor layer sequence (2) according to any of the preceding claims, in which exactly one prequantum pot (23) has a thickness between 2.2 nm and 3.4 nm inclusive and an indium content between 0.5% and 6% inclusive, wherein at least four and at most 30 principal quantum wells (32) are present and the principal quantum wells (32) each have a thickness between 2.2 nm and 3.4 nm inclusive and an indium content between 1% and 7% inclusive. [11] Semiconductor layer sequence (2) according to one of the preceding claims, wherein the second band gap of the principal quantum wells (32) is between 80% and 95% inclusive of the first band gap of the prequantum well (23). [12] Semiconductor layer sequence (2) according to one of the preceding claims, wherein all pairs of principal barrier layers (31) and principal quantum wells (32) in the multi-quantum well structure (3) are identical. [13] Optoelectronic semiconductor chip (1) with - a semiconductor layer sequence (2) according to one of the preceding claims, and - a substrate (6) which is a growth substrate of the semiconductor layer sequence (2). [14] Optoelectronic semiconductor chip (1) according to the preceding claim, wherein the substrate (6) is a sapphire substrate with a structured outgrowth surface, and wherein the semiconductor layer sequence (2) extends over the entire substrate (6) in a constant composition.

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