Radiation-emitting semiconductor body and semiconductor chip

Abstract

Radiation-emitting semiconductor body (1) with a semiconductor layer sequence (2) comprising an active region (20) intended for generating radiation, an n-conducting region (21), a p-conducting region (22) and a mirror layer (5), wherein - the active region (20) is arranged between the n-conducting region (21) and the p-conducting region (22); - the p-conducting region (22) has a current expansion layer (3) based on a phosphide compound semiconductor material; - the current expansion layer (3) is doped with a first dopant which is incorporated at phosphorus lattice sites, - the first dopant is carbon, - the current expansion layer (3) is lattice mismatched and partially or completely relaxed with respect to a semiconductor material adjacent on a side facing the active region (20), - the p-conducting region (22) between the current expansion layer (3) and the active region (20) has a sub-region (221), wherein the sub-region (221) is p-conducting doped with a second dopant different from the first dopant, - the flow expansion layer (3) is structured in the lateral direction such that it has at least one recess (35) which is completely surrounded in the lateral direction by material of the flow expansion layer (3), - a dielectric layer (55) is arranged locally between the mirror layer (5) and the current-expansion layer (3), which has one or a plurality of openings (550) in which the mirror layer (5) is electrically connected to the current-expansion layer (3), and - which at least one recess (35) and the openings (550) of the dielectric layer (55) are laterally spaced apart from each other.

Description

[0001] The present application relates to a radiation-emitting semiconductor body and a semiconductor chip with such a semiconductor body.

[0002] Radiation-emitting semiconductor bodies and semiconductor chips with such a semiconductor body are known from documents EP 2 950 355 A1, EP 2 009 706 A1, JP 2000 - 312 028 A, DE 102 53 160 A1 and US 2002 / 0 104 997 A1.

[0003] In radiation-emitting semiconductor chips based on phosphide compound semiconductor material, AlGaAs layers are often used for current expansion on the p-side. However, these layers can corrode, which can lead to chip failure. Furthermore, such layers exhibit comparatively high absorption of the light generated within the semiconductor chip. Alternatively, magnesium-doped GaP can be used. While this avoids susceptibility to moisture, it results in a significantly lower resistivity than AlGaAs. Additionally, magnesium can diffuse into the active region and create defects, leading to light loss.

[0004] One challenge is to achieve good flow expansion while simultaneously minimizing absorption losses and maintaining high moisture stability.

[0005] This problem is solved, among other things, by a semiconductor body according to claim 1 and a semiconductor chip with such a semiconductor body. Further embodiments and advantages are the subject of the dependent claims.

[0006] A radiation-emitting semiconductor body with a sequence of semiconductor layers is described. In the vertical direction, i.e., perpendicular to a principal plane of the semiconductor layers in the sequence, the semiconductor body extends between a first principal surface and a second principal surface. The semiconductor layer sequence is epitaxially deposited, for example, by MOCVD or MBE. The semiconductor layer sequence forms the semiconductor body, such that all layers of the semiconductor body consist of epitaxial material. In other words, the entire semiconductor body is composed of crystalline material.

[0007] According to at least one embodiment of the radiation-emitting semiconductor body, the semiconductor layer sequence comprises an active region intended for generating radiation, an n-type region, and a p-type region, wherein the active region is arranged between the n-type region and the p-type region. The active region is thus located in a pn junction.

[0008] The active area is specifically intended for generating radiation in the green, yellow, red or infrared spectral range.

[0009] According to at least one embodiment of the radiation-emitting semiconductor body, the active area is based on a phosphide compound semiconductor material or on an arsenide compound semiconductor material.

[0010] In this context, "based on phosphide compound semiconductor material" means that the material is a phosphide compound semiconductor material, preferably Al x In y Ga 1-x-y The material contains or consists of P, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, and x+y ≤ 1. This material does not necessarily have to have a mathematically exact composition according to the formula above. Rather, it may, for example, contain one or more dopants as well as additional components. For the sake of simplicity, however, the formula above only includes the essential components of the crystal lattice (Al, Ga, In, P), even though these may be partially replaced and / or supplemented by small amounts of other substances.

[0011] In this context, "based on arsenide compound semiconductor material" means that the material is an arsenide compound semiconductor material, preferably Al x In y Ga l-x-yThe material contains or consists of As, where 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, and x+y ≤ 1. This material does not necessarily have to have a mathematically exact composition according to the formula above. Rather, it may, for example, contain one or more dopants as well as additional components. For the sake of simplicity, however, the formula above only includes the essential components of the crystal lattice (Al, Ga, In, As), even though these may be partially replaced and / or supplemented by small amounts of other substances.

[0012] According to at least one embodiment of the radiation-emitting semiconductor body, the p-type region has a current-expansion layer. The current-expansion layer is thus part of the semiconductor body. In particular, the current-expansion layer is formed on the side of the p-type region facing away from the active region. For example, the current-expansion layer forms the second main surface of the semiconductor body. According to at least one embodiment of the radiation-emitting semiconductor body, the current-expansion layer is doped with a first dopant. The first dopant, in particular, causes p-type doping. In other words, the first dopant acts as an acceptor. For example, the first dopant is incorporated at group V lattice sites, in particular at phosphorus lattice sites.

[0013] In at least one embodiment of the radiation-emitting semiconductor body, the radiation-emitting semiconductor body comprises a sequence of semiconductor layers including an active region for generating radiation, an n-type region, and a p-type region, wherein the active region is located between the n-type region and the p-type region. The p-type region includes a current-expansion layer based on a phosphide compound semiconductor material. The current-expansion layer is doped with a first dopant material incorporated at phosphorus lattice sites.

[0014] It has been shown that such a current expansion layer enables the realization of a semiconductor body which, compared to a semiconductor body with an AlGaAs current expansion layer, is characterized by improved moisture stability and lower absorption losses. Furthermore, high conductivity and thus efficient current expansion can be achieved.

[0015] According to at least one embodiment of the radiation-emitting semiconductor body, the first dopant is a group IV element. Such an element acts as an acceptor when incorporated at a group V lattice site, such as a phosphorus lattice site.

[0016] For example, the first dopant is carbon. Carbon is characterized by particularly low diffusion within the semiconductor body. This effectively prevents damage to the semiconductor body, especially the active region, caused by diffusion of the first dopant into the active region and the associated loss of light transmission.

[0017] The current expansion layer, for example, has a doping concentration of between 1 × 10 17 cm -3 and 1 × 10 21 cm -3 , for example between 5 × 10 19 cm -3 and 5 × 10 20 cm -3 on.

[0018] According to at least one embodiment of the radiation-emitting semiconductor body, the current-expansion layer is lattice-mismatched and partially or completely relaxed with respect to a semiconductor material adjacent to the active region on the side of the semiconductor body. This means that the current-expansion layer is deposited with its intrinsic lattice constant, even though the intrinsic lattice constant differs from the lattice constant of the underlying semiconductor material. Thus, the material of the current-expansion layer has a different lattice constant within the semiconductor body than the underlying material of the semiconductor body.

[0019] Contrary to the usual approach of avoiding relaxation, a current-expansion layer is deliberately used that does not have the same lattice constant as the underlying semiconductor material and grows under neither compression nor tension. It has been shown that, despite the relaxation of the current-expansion layer, the semiconductor body exhibits overall improved properties.

[0020] According to at least one embodiment of the radiation-emitting semiconductor body, the current-expansion layer Al x In y Ga 1-x-y The current-expansion layer exhibits properties P with 0 ≤ × ≤ 0.05 and 0 ≤ y ≤ 0.05. Therefore, the current-expansion layer contains no aluminum or at least only a low aluminum content y. This simplifies the efficient incorporation of a group IV element such as carbon onto phosphorus lattice sites. Furthermore, the current-expansion layer contains no or only a comparatively small amount of indium.

[0021] According to at least one embodiment of the radiation-emitting semiconductor body, x = 0 and y = 0. The current-expansion layer is therefore formed by GaP and contains, at least nominally, neither aluminum nor indium.

[0022] According to at least one embodiment of the radiation-emitting semiconductor body, the p-type region between the current-expansion layer and the active region has a sub-region. This sub-region is, in particular, p-doped with a second dopant that differs from the first dopant.

[0023] The p-type region therefore has two regions doped with different dopants. For example, the first dopant is not present in the subregion. Furthermore, for example, the second dopant is not present in the current-expansion layer. For example, both the current-expansion layer and the subregion contain only exactly one dopant.

[0024] According to at least one embodiment of the radiation-emitting semiconductor body, the second dopant is incorporated at group III lattice sites. For example, the second dopant is a group II element, such as magnesium. The second dopant thus acts as an acceptor.

[0025] According to at least one embodiment of the radiation-emitting semiconductor body, a superlattice structure is arranged between the current-expansion layer and the active region. For example, the superlattice structure is arranged between the current-expansion layer and the subregion. By means of the superlattice structure, the risk of crystal defects propagating from the current-expansion layer towards the active region can be further suppressed.

[0026] For example, the superlattice structure has a plurality of first sublayers and a plurality of second sublayers, where the first and second sublayers differ from each other with respect to material. The layer thicknesses of the first and second sublayers are expediently so small that the layer thickness is below their respective critical thicknesses, thus preventing relaxations. The critical thickness is the layer thickness above which relaxations occur in lattice-mismatched material, such that the lattice-mismatched material no longer adopts the lattice constant of the underlying material.

[0027] According to at least one embodiment of the radiation-emitting semiconductor body, all layers of the semiconductor layer sequence, except for the current-expansion layer, are lattice-matched. In this context, "lattice-matched" means, in particular, that the relative deviation between the lattice constants is at most 2%. In other words, the current-expansion layer is the only relaxed semiconductor layer within the semiconductor layer sequence. The remaining layers are either lattice-matched with respect to the growth substrate, for example, gallium arsenide, or are grown under tension or compression.

[0028] According to at least one embodiment of the radiation-emitting semiconductor body, the current-expansion layer is structured in the lateral direction, i.e., in a direction extending along a principal plane of the semiconductor layers of the semiconductor layer sequence. For example, the current-expansion layer has at least one recess. The recess is, for example, completely surrounded in the lateral direction by material of the current-expansion layer.

[0029] Furthermore, a radiation-emitting semiconductor chip with such a semiconductor body is specified.

[0030] According to at least one embodiment of the radiation-emitting semiconductor chip, the semiconductor chip has a support on which the semiconductor body is arranged.

[0031] According to at least one embodiment of the radiation-emitting semiconductor chip, the support is different from a growth substrate for the semiconductor body. The support also serves, in particular, to mechanically stabilize the semiconductor body, so that the growth substrate is no longer required for this purpose and can be removed. Unlike the growth substrate, the support does not have to meet the high crystalline requirements of a growth substrate and can be selected with regard to other criteria, for example, with regard to its transmittance for radiation to be generated in the active region, its electrical or thermal conductivity, or its cost-effective availability.

[0032] According to at least one embodiment of the radiation-emitting semiconductor chip, a reflective layer is arranged between the substrate and the semiconductor body. The reflective layer is, in particular, designed as a metallic reflective layer. For example, gold is characterized by high reflectivity in the visible and infrared spectral ranges. Radiation emitted towards the substrate is reflected back by the reflective layer. Therefore, a material that would absorb the radiation generated in the active region during operation can also be used for the substrate.

[0033] According to at least one embodiment of the radiation-emitting semiconductor chip, the substrate is transparent to the radiation generated in the active area, and during operation of the semiconductor chip, at least part of the radiation escapes through the substrate, in particular also from at least one side surface of the substrate.

[0034] Further designs and advantages will become apparent from the following description of the exemplary embodiments in conjunction with the figures.

[0035] They show: Fig. 1A an embodiment of a semiconductor body in schematic sectional view; Fig. 1B an embodiment of a semiconductor chip with a semiconductor body in schematic sectional view; Fig. 1C an embodiment of a semiconductor chip with a semiconductor body in a schematic sectional view; and Fig. 2 another embodiment of a semiconductor body.

[0036] Identical, similar, or similarly effective elements in the figures are provided with the same reference symbols.

[0037] The figures are schematic representations and therefore not necessarily to scale. Rather, comparatively small elements and especially layer thicknesses may be exaggerated for clarity.

[0038] An embodiment of a radiation-emitting semiconductor body 1 is shown in Fig. Figure 1A is shown in a schematic sectional view. The semiconductor body 1 is formed by a sequence of semiconductor layers 2. For example, the sequence of semiconductor layers 2 is epitaxially deposited on a growth substrate, such as gallium arsenide. The growth substrate is in Fig. 1A not explicitly shown.

[0039] In a vertical direction, i.e. perpendicular to a principal extension plane of the semiconductor layers of the semiconductor layer sequence 2, the semiconductor body 1 extends between a first principal surface 11 and a second principal surface 12.

[0040] The semiconductor layer sequence 2 has an active region 20 intended for generating radiation, which is located between an n-conducting region 21 and a p-conducting region 22.

[0041] The active region 20 is based on a phosphide compound semiconductor material or an arsenide compound semiconductor material. For example, the active region 20 is formed as a quantum structure with a plurality of quantum layers 201 and barrier layers 202 arranged between them. By selecting the material composition of the phosphide compound semiconductor material or the arsenide compound semiconductor material and / or the layer thickness of the quantum layers 201, the emission wavelength of the radiation to be generated in the active region can be varied from the green, through the yellow and red, to the infrared spectral range.

[0042] The p-type region 22 has a current expansion layer 3.

[0043] The current expansion layer 3 forms the second main surface 12. The current expansion layer closes off the semiconductor body 1 on the p-side of the active region 20.

[0044] Current-expansion layer 3 is doped with a first dopant incorporated at phosphorus lattice sites, for example, a group IV element. Carbon is particularly suitable as a first dopant because high dopant concentrations and thus high electrical conductivities can be achieved with carbon. Furthermore, the diffusion of carbon is lower than that of other p-type dopants incorporated at group III lattice sites, such as magnesium. Carbon therefore does not cause defects in the active region. High, stable efficiency can thus be achieved more easily. The current-expansion layer, for example, has a dopant concentration of between 1 × 10⁻⁶ 17 cm -3 and 1 × 10 21 cm -3 , for example between 1 × 1019 cm -3 and 5 × 10 20 cm -3 on.

[0045] In particular, carbon-doped GaP material is suitable for the current expansion layer 3. However, the current expansion layer 3 can also contain small amounts of aluminum and / or indium, for example with an aluminum content x ≤ 0.05 and an indium content y ≤ 0.05.

[0046] Such a current expansion layer 3 is characterized by high transmission in the aforementioned spectral ranges for the radiation to be generated in the active region 20. Furthermore, such a current expansion layer is more moisture-stable compared to an AlGaAs current expansion layer. The current expansion layer 3 forms the second main surface 12 of the semiconductor body 1. Between the active region 20 and the current expansion layer 3, the p-type region 22 has a subregion 221. For subregion 221, for example, a phosphide compound semiconductor material with an aluminum content between 0.4 and 0.5 (inclusive) is suitable.

[0047] Unlike the other layers of the semiconductor layer sequence 2, the current expansion layer 3 is fully or partially relaxed and therefore does not have the lattice constant of the growth substrate, i.e., gallium arsenide. All semiconductor layers of the semiconductor layer sequence arranged on the side of the current expansion layer 3 facing the active region 20 thus have the same lattice constant.

[0048] The p-type region 22 further exhibits a subregion 221 on the side of the current-expansion layer 3 facing the active region 20. Subregion 221 is p-type doped by a second dopant. In particular, the second dopant is different from the first. For example, a group II element, such as magnesium, which is incorporated at group III lattice sites and acts as an acceptor, is suitable.

[0049] In Fig. Figure 1B shows a semiconductor chip 10 with such a semiconductor body 1. The semiconductor chip 10 has a substrate 7 on which the semiconductor body 1 with the semiconductor layer sequence 2 is arranged. The substrate 7 is attached to the semiconductor layer sequence 2 by means of a bonding layer 6, such as a solder layer or an electrically conductive adhesive layer.

[0050] In the illustrated embodiment, a mirror layer 5 is arranged between the support 7 and the semiconductor layer sequence 2. The mirror layer 5 also serves as the electrical contact for the current-expansion layer 3. A dielectric layer 55 is arranged locally between the mirror layer 5 and the current-expansion layer 3. The dielectric layer has one or more openings 550 in which the mirror layer is electrically connected to the current-expansion layer. The mirror layer therefore does not fully abut the second main surface 12. Radiation emitted in the active region 20 at relatively large angles to the vertical direction can be totally reflected by the dielectric layer 55, so that these radiation components are reflected with virtually no loss and can subsequently exit the semiconductor chip 10. Silicon oxide, for example, is suitable for the dielectric layer 55.

[0051] It has been shown that the current expansion layer 3 described above also exhibits improved adhesion to such a dielectric layer 55. This further increases the reliability of the semiconductor chip 10.

[0052] For external electrical contacting of the semiconductor chip 10, the semiconductor chip has a first contact 81 and a second contact 82. In the illustrated embodiment, the second contact is arranged on the side of the substrate 7 opposite the semiconductor layer sequence 2. The first contact 81 is arranged on the first main surface 11 of the semiconductor body 1 and is connected to the n-conducting region 21.

[0053] However, the arrangement of the first and second contacts can be varied within wide limits, as long as, by applying an external electrical voltage between the first contact 81 and the second contact 82, charge carriers from opposite sides can enter the active region 20 and recombine there by emitting radiation.

[0054] The reflective layer 6 reflects radiation emitted towards the substrate 7 back into the semiconductor body 1. The substrate 7 itself therefore does not need to be transparent to the radiation generated in the active region 20. For example, a semiconductor material such as silicon or germanium is suitable for the substrate. During operation of the semiconductor chip, the radiation is emitted predominantly from the first main surface 11 facing away from the substrate. Such a semiconductor chip is, to a good approximation, a surface emitter with a Lambertian radiation pattern.

[0055] In contrast to the described embodiment, the reflective layer 5 can also be omitted. In this case, a radiation-transparent material is particularly suitable for the substrate 7, such as GaP, so that the radiation generated in the active region 20 can pass through the substrate 7 and exit the semiconductor chip 10. In particular, the radiation can also exit, at least partially, through at least one side surface of the substrate. A semiconductor chip in which a significant portion of the radiation, for example at least 30% of the radiation, also exits laterally from the semiconductor chip is also referred to as a volume emitter.

[0056] In Fig. Figure 1C shows another embodiment of a semiconductor chip. This embodiment essentially corresponds to the one described in connection with Fig. The embodiment described in Figure 1B differs in that the current expansion layer 3 has a lateral structure. This structure is formed by a plurality of recesses 35 in the current expansion layer. The recesses are intended, for example, to disrupt waveguide effects in the semiconductor body 2. This increases the coupling efficiency. In the illustrated embodiment, the recesses 35 of the current expansion layer 3 and the openings 550 of the dielectric layer 55 are laterally spaced apart. However, in a top view, the recesses 35 and the openings 550 can also be arranged completely or at least partially overlapping next to each other. A contact layer 51 for electrical contacting of the current expansion layer 3 is arranged in the openings 550.Viewed vertically, the contact layer is positioned in certain locations between the current expansion layer 3 and the mirror layer 5. Such a contact layer can also be used in the other embodiments, but is not strictly necessary.

[0057] In Fig. Figure 2 shows a further embodiment of a semiconductor body in a schematic sectional view. This further embodiment essentially corresponds to the one described in connection with Fig. 1A described embodiment.

[0058] In contrast, the p-type region 22 has a superlattice structure 45. The superlattice structure 45 is arranged between the current-expansion layer 3 and the active region 20. In particular, the superlattice structure 45 is arranged between the current-expansion layer 3 and the subregion 221. The superlattice structure 45 has, for example, a plurality of first sublayers 451 and a plurality of second sublayers 452. For simplified representation, in Fig. Figure 2 shows only a first sublayer and a second sublayer. For example, GaP is suitable for the first sublayer and AlInP for the second sublayer.

[0059] The superlattice structure further reduces the risk of lattice defects propagating from the current-expansion layer 3 towards the active region 20. This prevents the resulting light loss.

[0060] Overall, the described semiconductor body and the semiconductor chip formed from it are characterized by high moisture stability, low light loss, and good current expansion due to high electrical conductivity combined with low absorption losses. Furthermore, the reliability of the semiconductor chip is improved due to the enhanced adhesion of a dielectric layer to this current expansion layer. Reference symbol list 1 Semiconductor body 10 Semiconductor chips 11 first main area 12 second main area 2 Semiconductor layer sequence 20 active area 201 quantum layer 202 Barrier layer 21 n-conducting area 22 p-conducting area 221 Sub-area 3 Current expansion layer 35 Exclusion 45 grids 451 first sub-shift 452 second sub-shift 5 Mirror layer 51 Contact layer 55 dielectric layer 550 opening 6. Compound layer 7 carriers 81 first contact 82 second contact

Claims

[1] Radiation-emitting semiconductor body (1) with a sequence of semiconductor layers (2) comprising an active region (20) for generating radiation, an n-type region (21), a p-type region (22) and a mirror layer (5), wherein - the active region (20) is arranged between the n-conducting region (21) and the p-conducting region (22); - the p-conducting region (22) has a current expansion layer (3) based on a phosphide compound semiconductor material; - the current expansion layer (3) is doped with a first dopant which is incorporated at phosphorus lattice sites, - the first dopant is carbon, - the current expansion layer (3) is lattice mismatched and partially or completely relaxed with respect to a semiconductor material adjacent on a side facing the active region (20), - the p-conducting region (22) between the current expansion layer (3) and the active region (20) has a sub-region (221), wherein the sub-region (221) is p-conducting doped with a second dopant different from the first dopant, - the flow expansion layer (3) is structured in the lateral direction such that it has at least one recess (35) which is completely surrounded in the lateral direction by material of the flow expansion layer (3), - a dielectric layer (55) is arranged locally between the mirror layer (5) and the current-expansion layer (3), which has one or a plurality of openings (550) in which the mirror layer (5) is electrically connected to the current-expansion layer (3), and - which at least one recess (35) and the openings (550) of the dielectric layer (55) are laterally spaced apart from each other. [2] Radiation-emitting semiconductor body according to claim 1, wherein the current expansion layer (3) has a doping concentration of at least 1 × 10 19 cm -3 exhibits. [3] Radiation-emitting semiconductor body according to one of the preceding claims, wherein the current-expansion layer (3) Al x In y Ga 1-x-y P with 0 ≤ x ≤ 0.05 and 0 ≤ y ≤ 0.

05. [4] Radiation-emitting semiconductor body according to claim 3, wherein x = 0 and y = 0. [5] Radiation-emitting semiconductor body according to one of the preceding claims, wherein the second dopant is incorporated on group III lattice sites. [6] Radiation-emitting semiconductor body according to one of the preceding claims, wherein a superlattice structure (45) is arranged between the current expansion layer (3) and the active region (20). [7] Radiation-emitting semiconductor body according to one of the preceding claims, wherein all layers of the semiconductor layer sequence (2) except the current expansion layer (3) are lattice-matched. [8] Radiation-emitting semiconductor chip (10) with a semiconductor body (1) according to one of the preceding claims, wherein the semiconductor chip (10) has a support (7) on which the semiconductor body (1) is arranged. [9] Radiation-emitting semiconductor chip according to claim 8, wherein the support (7) is different from a growth substrate for the semiconductor body (1). [10] Radiation-emitting semiconductor chip according to claim 9, wherein the mirror layer (5) is arranged between the support (7) and the semiconductor body (1). [11] Radiation-emitting semiconductor chip according to claim 9 or 10, wherein the carrier (7) is transparent to the radiation generated in the active area (20) and during operation of the semiconductor chip (10) at least some of the radiation passes through the carrier (7).

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