Optoelectronic component and method for its manufacture

Abstract

Optoelectronic component (10) with a semiconductor layer structure (100) based on the InGaN compound semiconductor system and having a quantum film structure (140) and a p-doped layer (160) arranged above the quantum film structure (140), where - the p-doped layer (160) comprises at least a first sublayer (161) and a second sublayer (162), - the second sublayer (162) has a higher degree of doping (323) than the first sublayer (161), - a spacer layer (150) is arranged between the quantum film structure (140) and the p-doped layer (160), which is directly adjacent to the quantum film structure (140) on one side and directly adjacent to the p-doped layer (160) on the opposite side, and - the degree of doping in the growth direction of the semiconductor layer structure (100) in the spacer layer (150) between the doping level of the quantum film structure (140) and the doping level of the p-doped layer (160) increases.

Description

[0001] The present invention relates to an optoelectronic component according to claim 1 and a method for manufacturing an optoelectronic component according to claim 12.

[0002] It is known that nitride semiconductor chips, such as optoelectronic nitride semiconductor chips, can be permanently damaged or destroyed by even very small electrostatic discharges (ESD). If a sapphire-containing substrate is used in the fabrication of such semiconductor chips, the epitaxial growth of a nitride semiconductor layer sequence results in a crystal with a high dislocation density. These dislocations act as leakage current paths, through which leakage currents can flow in the event of ESD exposure, potentially leading to damage or destruction of the nitride semiconductor chip.

[0003] To prevent damage from electrostatic discharges, protective measures are necessary. It is known to connect nitride semiconductor chips with separate protective diodes and arrange them in a common package. In the event of an ESD load, the charge pulse can dissipate via the protective diode without damaging the nitride semiconductor chip. However, the separate protective diode increases the required size of the common package.

[0004] The publications US 2012 / 0 313 109 A1, CA 2 322 490 A1, JP H09 - 293 937 A and EP 1 883 140 A1 are directed at optoelectronic semiconductor chips.

[0005] Publication JP 2013 - 58 622 A concerns an optoelectronic semiconductor chip.

[0006] One object of the present invention is to provide an optoelectronic component. This object is achieved by an optoelectronic component having the features of claim 1. A further object of the present invention is to provide a method for manufacturing an optoelectronic component. This object is achieved by a method having the features of claim 12. Various embodiments are specified in the dependent claims.

[0007] An optoelectronic device comprises a semiconductor layer structure with a quantum film structure and a p-doped layer positioned above the quantum film structure. The p-doped layer includes at least a first sublayer and a second sublayer. The second sublayer has a higher doping concentration than the first sublayer. Advantageously, the more heavily doped second sublayer exhibits higher electrical conductivity. In the event of ESD exposure of the optoelectronic device, a leakage current flowing through the semiconductor layer structure is thus spread out and distributed laterally in the second sublayer of the p-doped layer. This counteracts a narrow spatial confinement of the leakage current and prevents excessively high local current densities. Advantageously, this reduces the risk of damage to the optoelectronic device in the event of ESD exposure.This advantageously results in integrated ESD protection for the optoelectronic component, eliminating the need for measures that compromise the crystal quality of the semiconductor layer structure. Furthermore, the integrated ESD protection also eliminates the need for an external protection diode, leading to more cost-effective manufacturing and smaller component dimensions.

[0008] In one embodiment of the optoelectronic device, the first sublayer has a doping level of less than 5 × 10^18 per cubic centimeter and preferably 0. Advantageously, the first sublayer then exhibits a significantly reduced conductivity.

[0009] In one embodiment of the optoelectronic device, the second sublayer has a doping level between 1 × 10^18 per cubic centimeter and 1.5 × 10^20 per cubic centimeter, preferably between 2 × 10^19 per cubic centimeter and 8 × 10^19 per cubic centimeter. For example, the second sublayer can have a doping level of 4 × 10^19 per cubic centimeter. Advantageously, the second sublayer then exhibits a significantly higher conductivity than the first sublayer. This allows leakage currents flowing parallel to the growth direction through the semiconductor layer structure of the optoelectronic device to be spread out laterally in the second sublayer.

[0010] In one embodiment of the optoelectronic component, the first sublayer and the second sublayer each have a thickness between 1 nm and 50 nm, preferably a thickness between 5 nm and 20 nm, and particularly preferably a thickness between 8 nm and 12 nm. For example, the first sublayer and the second sublayer can each have a thickness of 10 nm. Sublayers of this thickness have proven to be particularly advantageous in tests.

[0011] In one embodiment of the optoelectronic device, the p-doped layer comprises several first sublayers and second sublayers, which alternate with one another. Advantageously, the multiple second sublayers each distribute a leakage current flowing in the growth direction through the semiconductor layer structure of the optoelectronic device in the event of an ESD load, thereby reducing the risk of damage to the optoelectronic device from such a leakage current.

[0012] In one embodiment of the optoelectronic device, the p-doped layer comprises between 1 and 50 first sublayers, preferably three. Advantageously, experiments have shown that a number of three first sublayers of the p-doped layer can produce a particularly beneficial effect.

[0013] A spacer layer is arranged between the quantum film structure and the p-doped layer. Advantageously, this prevents the doping of the p-doped layer from adversely affecting the quantum film structure.

[0014] In one embodiment of the optoelectronic device, the spacer layer has a thickness between 2 nm and 120 nm. Preferably, the spacer layer has a thickness between 10 nm and 50 nm. Particularly preferably, the spacer layer has a thickness between 20 nm and 30 nm. For example, the spacer layer can have a thickness of approximately 25 nm. A spacer layer of this thickness advantageously prevents a negative influence on the quantum film structure by the doping of the p-doped layer, without excessively spacing the quantum film structure and the p-doped layer apart.

[0015] The spacer layer comprises a first sublayer with a lower doping level and a second sublayer with a higher doping level. The first sublayer is positioned closer to the quantum film structure than the second sublayer. This results in an increase in the doping level in the growth direction of the semiconductor layer structure within the spacer layer, between the doping level of the quantum film structure and the doping level of the p-doped layer. This increase in doping level within the spacer layer can be, for example, stepwise or continuous.

[0016] In one embodiment of the optoelectronic component, the p-doped layer is doped with magnesium, carbon, or boron. These dopants have proven advantageously suitable. Doping the p-doped layer with magnesium is particularly preferred.

[0017] In one embodiment of the optoelectronic component, the p-doped layer has an indium content of less than 30%, preferably 0%. Furthermore, the p-doped layer has an aluminum content of less than 30%, preferably 0%. Advantageously, the band gap in the p-doped layer can be adjusted by varying the proportions of indium and / or aluminum.

[0018] A method for fabricating an optoelectronic device comprises steps for providing a substrate, growing a quantum film structure, and growing a p-doped layer, wherein the growth of the p-doped layer includes the growth of at least a first sublayer and a second sublayer, the second sublayer having a higher degree of doping than the first sublayer. Advantageously, this method can fabricate an optoelectronic device with a semiconductor layer structure that incorporates integrated ESD protection. The ESD protection is achieved by the more highly doped second sublayer of the p-doped layer, which can dissipate a leakage current flowing through the semiconductor layer structure in the lateral direction in the event of an ESD load.This advantageously reduces the risk of a critically high current density in the event of ESD exposure of the optoelectronic component, and thus also the risk of damage to the semiconductor layer structure of the optoelectronic component. Advantageously, the optoelectronic component does not require an external protection diode, allowing for a space-saving package. Other measures to reduce the risk of damage from ESD exposure, which could potentially lead to a deterioration of the crystal quality in the semiconductor layer structure and thus a reduction in the efficiency of the optoelectronic component, are also advantageously unnecessary.

[0019] In one embodiment of the method, several first sublayers and second sublayers are grown alternately. Advantageously, the several second sublayers can then each cause a distribution of a leakage current in a lateral direction, thereby achieving particularly effective protection against damage from ESD exposure.

[0020] A spacer layer is grown between the quantum film structure and the p-doped layer. Advantageously, this spacer layer prevents the doping of the p-doped layer from adversely affecting the quantum film structure.

[0021] The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more readily understandable in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawings. Fig. 1 a schematic cross-sectional view of a semiconductor layer structure of an optoelectronic device; Fig. 2. A first growth diagram to illustrate a process for producing the semiconductor layer structure; and Fig. 3. A second growth diagram to explain the manufacturing process.

[0022] Fig. Figure 1 shows a highly schematic cross-section through a semiconductor layer structure 100 of an optoelectronic device 10. The optoelectronic device 10 can, for example, be a light-emitting diode (LED) device. The semiconductor layer structure 100 comprises layers of nitride compound semiconductor materials. The semiconductor layer structure 100 has layers of an InGaN compound semiconductor system.

[0023] The semiconductor layer structure 100 of the optoelectronic device 10 can be produced by epitaxial growth. Fig. Figure 2 shows a schematic first growth diagram 200 to illustrate such a manufacturing process. Fig. Figure 3 shows a schematic second growth diagram 300 for further explanation of the manufacturing process. A progressive time 210 is plotted on the horizontal axes of both growth diagrams 200 and 300. A vertical axis of the first growth diagram 200 shows a band gap energy 220 of a material grown epitaxially at a specific time. A vertical axis of the second growth diagram 300 shows a p-doping level 320 of a layer grown epitaxially at a specific time.

[0024] The fabrication of the semiconductor layer structure 100 of the optoelectronic device 10 begins with the provision of a substrate 110. The substrate 110 can, for example, be sapphire. To compensate for a lattice mismatch between a lattice constant of the substrate 110 material and the lattice constant of the nitride compound semiconductor system of the semiconductor layer structure 100, a buffer layer 120 can first be grown. The buffer layer 120 can, for example, be GaN. Further layers can also be grown before or after the buffer layer 120. Fig. One layer, not shown, is built up. The buffer layer 120 can also be omitted.

[0025] After the epitaxial growth of the buffer layer 120 and any further layers, epitaxial growth of an n-doped layer 130 begins at a first time point 211. The n-doped layer 130 is grown from a material with a second band gap energy 222. The material with the second band gap energy 222 can be, for example, GaN. The n-doped layer 130 is deposited with n-doping. P-doping is preferably not applied. Thus, the epitaxially grown n-doped layer 130 has a first p-doping level 321, which preferably has the value 0, as shown in the second growth diagram 300. Fig. 3 can be seen. The growth of the n-doped layer 130 continues until a second time point 212.

[0026] At the second time point 212, an epitaxial growth of a quantum film structure 140 begins. The epitaxial growth of the quantum film structure 140 lasts until a third time point 213.

[0027] The quantum film structure 140 comprises a plurality of quantum films spaced apart in the growth direction, which are created by the alternating growth of a material with a first band gap energy 221 and a material with a second band gap energy 222. The first band gap energy 221 is lower than the second band gap energy 222. The material with the first band gap energy 221 is InGaN. The material with the second band gap energy 222 can, for example, be GaN. The sections of the quantum film structure 140 produced from the material with the first band gap energy 221 form quantum films, while the regions of the quantum film structure 140 produced from the material with the second band gap energy 222 form barriers arranged between the quantum films.Overall, the quantum film structure 140 can be constructed with, for example, three to fifteen quantum films, preferably with three to eight quantum films, and most preferably with five quantum films.

[0028] The quantum film structure 140 is also created with p-doping with the first doping level 321, preferably without any p-doping at all.

[0029] From the third time point 213, a spacer layer 150 of the semiconductor layer structure 100 is grown. The spacer layer 150 is grown from a material with the second bandgap energy 222, which, for example, has GaN. The growth of the spacer layer 150 continues until a fifth time point 215.

[0030] The spacer layer 150 is deposited in the growth direction of the semiconductor layer structure 100 with a first layer thickness 153. The first layer thickness 153 can be between 2 nm and 120 nm. Preferably, the first layer thickness 153 is between 10 nm and 50 nm. Particularly preferably, the first layer thickness 153 is between 20 nm and 30 nm. For example, the first layer thickness 153 can be 25 nm.

[0031] The spacer layer 150 serves to separate the quantum film structure 140 with the low first doping level 321 from a subsequent p-doped layer 160 with a higher doping level in the semiconductor layer structure 100, in order to avoid an adverse influence on the quantum film structure 140 by the doping of the p-doped layer 160.

[0032] Within the spacer layer 150, the p-doping level 320 of the spacer layer 150 is increased from the first doping level 321 to a higher third doping level 323. The increase in the p-doping level within the spacer layer 150 can, for example, occur continuously over the entire thickness 153 of the spacer layer 150 in the growth direction of the semiconductor layer structure 100, or over a portion of the thickness 153 of the spacer layer 150 in the growth direction of the semiconductor layer structure 100. In this case, the spacer layer 150 is gradient-doped.

[0033] However, the increase in the p-doping level 320 of the spacer layer 150 in the growth direction of the semiconductor layer structure 100 can also occur in several stages or, as in Fig. 1 and Fig. Figure 3 schematically depicts the process occurring in a single step. In this case, the spacer layer 150 is subdivided in the growth direction of the semiconductor layer structure 100 into a first spacer sublayer 151 and a second spacer sublayer 152. The first spacer sublayer 151 borders the quantum film structure 140. The second spacer sublayer 152 borders the first spacer sublayer 151 and the p-doped layer 160 following the spacer layer 150. The first spacer sublayer 151 is grown between time point 213 and time point 214. Subsequently, the second spacer sublayer 152 is grown between time point 214 and time point 215. The first spacer sublayer 151 is grown with the first doping level 321. The second spacer sublayer 152 is grown with the third doping level 323.

[0034] At time 215, the epitaxial growth of the p-doped layer 160 of the semiconductor layer structure 100 begins. The p-doped layer 160 is formed from successive sublayers in the growth direction of the semiconductor layer structure 100. At a minimum, the p-doped layer 160 comprises a first sublayer 161, which is epitaxially grown during a first sub-period 311, and a second sublayer 162, which is grown during a second sub-period 312 that follows the first sub-period 311. Preferably, however, the p-doped layer 160 comprises a plurality of first sublayers 161 and second sublayers 162, which alternate with one another. For example, the p-doped layer 160 can comprise between 1 and 50 first sublayers 161 and a corresponding number of second sublayers 162. Preferably, the p-doped layer 160 comprises three first sublayers 161 and three second sublayers 162.

[0035] All first sublayers 161 of the p-doped layer 160 have a second layer thickness 163 in the growth direction of the semiconductor layer structure 100. All second sublayers 162 of the p-doped layer 160 each have a third layer thickness 164 in the growth direction of the semiconductor layer structure 100. The second layer thickness 163 and the third layer thickness 164 can be the same or different. For example, the second layer thickness 163 and the third layer thickness 164 can be between 1 nm and 50 nm. Preferably, the second layer thickness 163 and the third layer thickness 164 are between 5 nm and 20 nm. Particularly preferably, the second layer thickness 163 and the third layer thickness 164 have values ​​between 8 nm and 12 nm. For example, the second layer thickness 163 and the third layer thickness 164 can each be 10 nm.

[0036] The layer thicknesses of the first sublayers 161 and the second sublayers 162 of the p-doped layer 160 can also vary in the growth direction of the semiconductor layer structure 100. In this case, different first sublayers 161 have different layer thicknesses and / or different second sublayers 162 have different layer thicknesses.

[0037] The first sublayers 161 of the p-doped layer 160 are grown with p-doping of a second doping level 322. The second doping level 322 is greater than or equal to the first doping level 321 and less than the third doping level 323. The second doping level 322 is less than 5 × 10^18 per cubic centimeter. Preferably, the second doping level 322 has the value 0.

[0038] The second sublayers 162 of the p-doped layer 160 are grown with p-doping of the third doping level 323. The third doping level 323 lies between 1 × 10^18 per cubic centimeter and 1.5 × 10^20 per cubic centimeter. Preferably, the third doping level 323 lies between 2 × 10^19 per cubic centimeter and 8 × 10^19 per cubic centimeter. For example, the third doping level 323 can have a value of 4 × 10^19 per cubic centimeter.

[0039] It is also possible that the doping levels of two or more first sublayers 161 of the p-doped layer 160 and / or the doping levels of two or more second sublayers 162 of the p-doped layer 160 differ from each other. For example, two consecutive second sublayers 162 of the p-doped layer 160 can have p-dopings with different doping levels.

[0040] The p-doped layer 160 is preferably doped with magnesium. However, it is also possible, for example, to dope the p-doped layer 160 with other dopants such as carbon or boron.

[0041] The epitaxial growth of the p-doped layer 160 of the semiconductor layer structure 100 proceeds up to a sixth time point 216. Subsequently, further layers of the semiconductor layer structure 100 can be grown, which are in Fig. 1 are not shown. Reference symbol list 10 optoelectronic component 100 semiconductor layer structure 110 substrate 120 buffer layer 130 n-doped layer 140 Quantum film structure 150 spacer layer 151 first spacer sublayer 152 second spacer sublayer 153 first layer thickness (d1) 160 p-doped layer 161 first sub-shift 162 second sub-shift 163 second layer thickness (d2) 164 third layer thickness (d3) 200 first growth chart 210 Time 211 first point in time 212 second point in time 213 third point in time 214 fourth point in time 215 fifth point in time 216 sixth point in time 220 band gap energy 221 first band gap energy (InGaN) 222 second band gap energy (GaN) 300 second growth chart 311 first partial period 312 second partial period 320 p-doping level 321 first degree of doping (x1 = 0) 322 second degree of doping (x2) 323 third degree of doping (x3)

Claims

Optoelectronic device (10) with a semiconductor layer structure (100) based on the InGaN compound semiconductor system, comprising a quantum film structure (140) and a p-doped layer (160) arranged above the quantum film structure (140), wherein: - the p-doped layer (160) comprises at least a first sublayer (161) and a second sublayer (162), - the second sublayer (162) has a higher degree of doping (323) than the first sublayer (161), - a spacer layer (150) is arranged between the quantum film structure (140) and the p-doped layer (160), which is directly adjacent to the quantum film structure (140) on one side and directly adjacent to the p-doped layer (160) on the opposite side, and - a degree of doping in the growth direction of the semiconductor layer structure (100) is present in the The distance layer (150) between the doping level of the quantum film structure (140) and the doping level of the p-doped layer (160) is increased. Optoelectronic component (10) according to claim 1, wherein the first sublayer (161) has a doping level (322) that is less than 5 × 10^18 per cubic centimeter and preferably 0. Optoelectronic component (10) according to one of the preceding claims, wherein the second sublayer (162) has a doping level (323) that is between 1 × 10^18 per cubic centimeter and 1.5 × 10^20 per cubic centimeter, preferably between 2 × 10^19 per cubic centimeter and 8 × 10^19 per cubic centimeter. Optoelectronic component (10) according to one of the preceding claims, wherein the first sublayer (161) and the second sublayer (162) each have a thickness (163, 164) between 1 nm and 50 nm, preferably a thickness (163, 164) between 5 nm and 20 nm, particularly preferably a thickness (163, 164) between 8 nm and 12 nm. Optoelectronic device (10) according to one of the preceding claims, wherein the p-doped layer (160) comprises several first sublayers (161) and second sublayers (162) that alternate one another. Optoelectronic component (10) according to claim 5, wherein the p-doped layer (160) comprises between 1 and 50 first sublayers (161), preferably 3 first sublayers (161). Optoelectronic component (10) according to one of claims 5 and 6, wherein two second sublayers (162) have different doping levels (323). Optoelectronic component (10) according to one of the preceding claims, wherein the spacer layer (150) has a thickness (153) between 2 nm and 120 nm, preferably a thickness (153) between 10 nm and 50 nm, particularly preferably a thickness (153) between 20 nm and 30 nm. Optoelectronic device (10) according to one of the preceding claims, wherein the spacer layer (150) comprises a first spacer sublayer (151) with a lower degree of doping (321) and a second spacer sublayer (152) with a higher degree of doping (323), wherein the first spacer sublayer (151) is arranged closer to the quantum film structure (140) than the second spacer sublayer (152). Optoelectronic device (10) according to one of the preceding claims, wherein the p-doped layer (160) is doped with magnesium, carbon or boron. Optoelectronic component (10) according to one of the preceding claims, wherein the p-doped layer (160) has an indium content of less than 30%, preferably an indium content of 0%, wherein the p-doped layer (160) has an aluminum content of less than 30%, preferably an aluminum content of 0%. Method for fabricating an optoelectronic device (10) comprising the following steps: - providing a substrate (110); - growing a quantum film structure (140) of a semiconductor layer structure (100) based on the InGaN compound semiconductor system; - growing a spacer layer (150) of the semiconductor layer structure (100);- Growth of a p-doped layer (160) of the semiconductor layer structure (100), wherein - the growth of the p-doped layer (160) comprises the growth of at least a first sublayer (161) and a second sublayer (162), the second sublayer (162) having a higher degree of doping (323) than the first sublayer (161), - the spacer layer (150) is arranged between the quantum film structure (140) and the p-doped layer (160) such that the spacer layer (150) is directly adjacent to the quantum film structure (140) on one side and directly adjacent to the p-doped layer (160) on the opposite side, and - the degree of doping in the growth direction of the semiconductor layer structure (100) in the spacer layer (150) is increased between the doping level of the quantum film structure (140) and the doping level of the p-doped layer (160). becomes.; Method according to claim 12, wherein several first sublayers (161) and second sublayers (162) are grown alternately.

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