Optoelectronic semiconductor body and light-emitting diode

Abstract

Optoelectronic semiconductor body (10) with - an active region (1) comprising a quantum well (1a) which is designed to generate electromagnetic radiation, - a first region (2) designed to prevent the passage of charge carriers from the active region (1), - a second region (4) which is designed to prevent the passage of charge carriers from the active region (1), wherein - the semiconductor body (10) is based on a nitride compound semiconductor material, - the first region (2) directly borders on the p-side of the active region (1), - the second region (4) is arranged on a side of the first region (2) facing away from the active region (1), - the first region (2) has an electronic band gap (E2) which is larger than an electronic band gap (E1) of the quantum well (1a) and smaller than or equal to an electronic band gap (E4) of the second region (4), - the first area (2) and the second area (4) contain aluminum, - an intermediate region (3) is arranged between the first region (2) and the second region (4), wherein the intermediate region (3) has an electronic band gap (E3a, E3b, E3c, E3d, E3e) which is larger than the electronic band gap (E1) of the quantum well (1a) and which is smaller than the electronic band gaps (E2) of the first region (2) and the second region (4), wherein the intermediate region (3) is at least partially free of aluminum, - the intermediate region (3) has at least two subregions (3a, 3b, 3c, 3d, 3e) which differ from one another in their material composition and their electronic band gap, - the first region (2) and the intermediate region (3) are n-doped, and - the second region (4) is p-doped.

Description

[0001] An optoelectronic semiconductor body is specified. Furthermore, a light-emitting diode with such an optoelectronic semiconductor body is specified.

[0002] The publications US 2008 / 0 073 658 A1, US 2012 / 0 012 815 A1, US 2012 / 0 145 993 A1, EP 2 722 897 A and US 2014 / 0 191 192 A1 describe semiconductor bodies.

[0003] One problem to be solved is to provide a semiconductor body and a light-emitting diode with such a semiconductor body which have a particularly favorable aging behavior.

[0004] This object is achieved by an optoelectronic semiconductor body according to claim 1 and a light-emitting diode according to claim 6. Advantageous embodiments are the subject of the dependent claims.

[0005] An optoelectronic semiconductor body is specified. The optoelectronic semiconductor body can, for example, be a radiation-emitting semiconductor body that can be used in a light-emitting diode or a laser diode.

[0006] The optoelectronic semiconductor body comprises an active region configured to generate electromagnetic radiation. For this purpose, the active region comprises at least one quantum well, in particular a plurality of quantum wells separated from one another by barriers.

[0007] The active region can in particular be designed to generate UV radiation or blue light during operation.

[0008] The semiconductor body comprises a first region configured to impede the passage of charge carriers, in particular electrons, from the active region. The first region is therefore a region that blocks charge carriers, in particular electrons, from the active region, so that they are more likely to remain in the active region than would be the case without the first region. The first region can therefore contribute to limiting or preventing the loss of charge carriers, in particular electrons, in the active region.

[0009] The optoelectronic semiconductor body comprises a second region configured to impede the passage of charge carriers, in particular electrons, from the active region. In other words, in addition to the first region, the optoelectronic semiconductor body comprises a further region configured to impede or prevent the escape of charge carriers, in particular electrons, from the active region. The first region and the second region thus ensure that the probability of charge carriers, in particular electrons, escaping from the active region is reduced.

[0010] The optoelectronic semiconductor body is based on a nitride compound semiconductor material. This means here and below that the semiconductor body or at least a part thereof, particularly preferably at least the active region, the first region and the second region, is based on a nitride compound semiconductor material, preferably Al n Ga m In 1-n-m N or consists of it, where 0 ≤ n ≤ 1, 0 ≤ m ≤ 1 and n+m ≤ 1. This material does not necessarily have to have a mathematically exact composition according to the above formula. Rather, it can, for example, contain one or more dopants as well as additional components. For the sake of simplicity, however, the above formula only includes the essential components of the crystal lattice (Al, Ga, In, N), even if these may be partially replaced and / or supplemented by small amounts of other substances.

[0011] The first region directly borders the active region on the p-side. This means that in a direction transverse or perpendicular to the main extension plane of the semiconductor body, for example, in a direction parallel or antiparallel to the growth direction of the semiconductor body, the first region directly adjoins the active region. The first region is arranged on a side of the active region facing the p-doped side of the semiconductor body and is therefore located on the p-side of the active region.

[0012] The second region is arranged on a side of the first region facing away from the active region. This means that the first region is arranged between the second region and the active region. Additional layers or regions can be arranged between the first region and the second region. Furthermore, it is possible for the first region and the second region to be directly adjacent to one another.

[0013] The regions of the optoelectronic semiconductor body preferably extend over the entire cross section of the semiconductor body and have a predeterminable thickness in a vertical direction, perpendicular to the main extension plane of the semiconductor body.

[0014] The first region has an electronic band gap that is larger than the electronic band gap of the quantum well and less than or equal to the electronic band gap of the second region. In particular, the electronic band gap of the first region is larger than the electronic band gap of each quantum well in the active region. Preferably, the electronic band gap of the second region is larger than the electronic band gap of the first region.

[0015] The first region and the second region contain aluminum. This means that the first region and the second region are formed, for example, with AlGaN, with the aluminum concentration being, for example, at least 2 percent, in particular at least 5 percent. The first region and the second region can, in particular, be free of indium, or the indium concentration in these regions can be very low, for example, less than 1%. By using aluminum in the first and second regions, an electronic band gap that is larger than the electronic band gap of the quantum well can be set particularly efficiently.

[0016] According to at least one embodiment, an optoelectronic semiconductor body is specified with - an active region comprising a quantum well designed to generate electromagnetic radiation, - a first region designed to prevent the passage of charge carriers from the active region, - a second region designed to prevent the passage of charge carriers from the active region, wherein - the semiconductor body is based on a nitride compound semiconductor material, - the first region directly borders the active region on the p-side, - the second region is arranged on a side of the first region facing away from the active region, - the first region has an electronic band gap that is larger than the electronic band gap of the quantum well and smaller than or equal to the electronic band gap of the second region, and - the first area and the second area contain aluminum.

[0017] An optoelectronic semiconductor body described here is based, among other things, on the consideration that a suitable doping profile for the p-dopant of the semiconductor body enables an optoelectronic semiconductor body that can generate electromagnetic radiation of high efficiency for a long time.

[0018] For this reason, it is necessary to control the diffusion of the p-dopant or defects (e.g. point defects) in the semiconductor body in a way that allows efficient injection of holes into the active region without the p-dopant or doping-induced defects or impurities being able to enter the p-side quantum wells.

[0019] The p-dopant, for example, is magnesium, which tends to diffuse in the nitride compound semiconductor material-based semiconductor body and can greatly reduce the efficiency of radiation generation when entering the active region.

[0020] To limit the diffusion of the p-dopant, it would be possible, for example, to introduce nominally undoped regions formed with aluminum-free layers between the active region and the p-doped region. The dopant profile can also be adjusted by precisely controlling the growth temperatures, which can be used to control the diffusion of the p-dopant. However, temperature fluctuations during the growth of the p-side of the semiconductor body then negatively impact efficiency and aging stability.

[0021] A semiconductor body described here is based, among other things, on the discovery that a first region comprising aluminum, which is arranged directly at the active region and has an electronic band gap that is larger than the electronic band gap of the active region, can increase the confinement of holes and electrons in the active region. The first region thus forms a charge carrier blocking layer, in particular also an electron blocking layer. Furthermore, the boundary layer defined by the junction acts as a barrier for migrating defects or diffusing foreign atoms or dopants.

[0022] The second region, which has an electronic band gap that is equal to or larger than the electronic band gap of the first region, then further enhances the capture of charge carriers and can, for example, be designed to inject holes into the active region due to appropriate doping.

[0023] The loss of charge carriers, especially electrons, can lead to a reduction in the internal quantum efficiency of the active region (so-called "droop"), especially for larger operating currents. This problem is mitigated by the first and second regions.

[0024] Because the first region is arranged between the second region and the active region and, for example, has a band gap that is smaller than the band gap of the second region but larger than the band gap of the quantum well in the active region, the first region can act as a diffusion barrier for the passage of the p-dopant or other foreign atoms or defects.

[0025] An intermediate region is arranged between the first region and the second region, the intermediate region having an electronic band gap that is larger than the electronic band gap of the quantum well and smaller than the electronic band gap of the first region and the second region.

[0026] In particular, the electronic band gap is larger than the electronic band gap of any quantum well in the active region. The intermediate region is thus designed to hinder or prevent the passage of electrons from the active region. Furthermore, the intermediate region serves to hinder the diffusion of the p-type dopant into the active region.

[0027] The intermediate region is partially or completely free of aluminum. The fact that the intermediate region is partially free of aluminum can mean, in particular, that at least one layer or layer sequence of the intermediate region is free of aluminum. This means that no aluminum is introduced into the intermediate region during the production of this layer or layer sequence.

[0028] The intermediate region comprises at least two subregions that differ from each other in their material composition and electronic band gaps. The subregions are formed, for example, as layers that fill the entire cross-section of the semiconductor body and have a predeterminable thickness in the vertical direction.

[0029] For example, the intermediate region has five or more subregions that differ in their material composition, at least in pairs. For example, two directly adjacent subregions differ in their material composition, whereas a subregion can be bordered on opposite sides by subregions that have the same material composition and the same electronic band gap, which differ from the material composition and the electronic band gap of the directly adjacent subregion. For example, subregions with higher and lower band gaps can be arranged alternately along the vertical direction, with the band gap of each subregion being larger than the band gap of the quantum well and smaller than the band gap of the first and second regions.

[0030] The fact that the intermediate region is partially free of aluminum can mean, in particular, that at least a sub-region of the intermediate region is free of aluminum. This means that no aluminum is introduced into the intermediate region during the production of this sub-region.

[0031] According to at least one embodiment of the optoelectronic semiconductor body, the intermediate region directly borders the first region and the second region. This means that, in the vertical direction, the active region is directly followed by the first region, the first region is directly followed by the intermediate region, and the intermediate region is directly followed by the second region. This sequence of regions ensures efficient confinement of charge carriers in the active region and forms an efficient barrier against the diffusion of p-dopant into the active region.

[0032] According to at least one embodiment of the optoelectronic semiconductor body, directly adjacent subregions of the intermediate region differ from one another in terms of their band gap. As a result, several interfaces are formed between subregions in the intermediate region, at which a jump in the band gap occurs. Surprisingly, it has been found that precisely these interfaces between the subregions efficiently prevent diffusion of the p-dopant, in particular the diffusion of magnesium, into the active region.

[0033] According to at least one embodiment of the optoelectronic semiconductor body, the second region has an aluminum concentration that is greater than the aluminum concentration in the first region. For example, the first region has an aluminum concentration that is greater than 5 percent. The second region then has an aluminum concentration that is greater than 5 percent, in particular an aluminum concentration that is greater than 10 percent.

[0034] The second region is p-doped. This means that the second region is, for example, the region of the semiconductor body closest to the active region, which is p-doped. For example, the second region is doped with magnesium and has a dopant concentration of at least 10 19 / cm 3 In a further embodiment, p-doping can be realized using alternative dopants or foreign atoms such as C, Be, etc.

[0035] According to at least one embodiment of the optoelectronic semiconductor body, the first region and the intermediate region are n-doped.

[0036] A p-dopant can enter the first region and the intermediate region to a small extent through diffusion processes during the fabrication of subsequent regions. For example, the concentration of the p-dopant in the two regions is then at most 10 20 / cm 3 In particular, the concentration of the p-dopant is lower than in the second region.

[0037] Furthermore, the regions are slightly n-doped. For example, doping can be achieved during silicon fabrication by adding silane (SiH4). This results in n-co-doping, which can lead to the formation of a particularly sharp boundary between the n-doped region and the p-doped region of the semiconductor body. In particular, co-doping can hinder diffusion processes of the p-dopant toward the active region.

[0038] According to at least one embodiment of the semiconductor body, the first region is covered with Al y1 Ga 1-y1 N or with Al y1 In x Ga 1-y1 N, where y1 > 0.05 and x < 0.01. The first region has, for example, a thickness between at least 1 nm and at most 5 nm. The intermediate region has a sub-region which is coated with In x Ga 1-xN, where x > 0.01 and x < 0.05, wherein the sub-region has, for example, a thickness of at least 0.05 nm and at most 5 nm. Furthermore, the intermediate region has a sub-region formed with GaN and has, for example, a thickness of at least 0.5 nm and at most 5 nm. The second region is then covered with Al y2 Ga 1-y2 N or with Al y2 In x Ga 1-y2 N, where y2 > y1 and x<0.01 and the second region has, for example, a thickness of at least 1 nm and at most 20 nm.

[0039] Such a configuration of the first region, the intermediate region and the second region proves to be particularly advantageous with regard to the confinement of charge carriers in the active region and the obstruction of diffusion of the p-dopant into the active region.

[0040] Furthermore, a light-emitting diode is specified. The light-emitting diode comprises an optoelectronic semiconductor body described here. This means that all features disclosed for the semiconductor body are also disclosed for the light-emitting diode, and vice versa. The light-emitting diode further comprises first and second connection points configured for electrically contacting the semiconductor body.

[0041] The light-emitting diode is designed to emit electromagnetic radiation with a peak wavelength of less than 480 nm, in particular less than 400 nm, during operation. In particular, the light-emitting diode is designed to emit electromagnetic radiation with a peak wavelength between 360 nm and 480 nm, in particular between 360 nm and 395 nm. It has been found that, due to the improved confinement of charge carriers in the active region for an optoelectronic semiconductor body described here, the use of the semiconductor body for generating UV radiation, in particular UVA radiation and blue light, is particularly advantageous.

[0042] In the following, the optoelectronic semiconductor body described here and the light-emitting diode described here are explained in more detail using exemplary embodiments and the associated figures.

[0043] Based on the schematic representation of the Fig. 1 an embodiment of an optoelectronic semiconductor body described here is explained in more detail.

[0044] Based on the graphical representation of the Fig. 2 the advantages of an optoelectronic semiconductor body described here are explained in more detail.

[0045] Based on the schematic sectional view of the Fig. 3 an embodiment of a light-emitting diode described here is explained in more detail.

[0046] Identical, similar, or functionally identical elements are provided with the same reference numerals in the figures. The figures and the relative sizes of the elements depicted in the figures are not to be considered to scale. Rather, individual elements may be exaggerated for clarity and / or clarity.

[0047] The Fig. 1 schematically shows a band diagram for an optoelectronic semiconductor body described here. The optoelectronic semiconductor body comprises an active region 1, which comprises at least one quantum well 1a, in particular a multiple quantum well structure with a plurality of quantum wells. The active region 1 preferably comprises five identical quantum wells 1a, between each of which a barrier is arranged. The quantum wells 1a each have a thickness of, for example, 3 nm, and the barriers each have a thickness of, for example, 4.7 nm. The quantum wells 1a are formed with InGaN, and the barriers with AlGaN.

[0048] On the P-side, the first region 2 directly borders on the active region 1. The first region 2 is in this case covered with Al y1 Ga 1-y1 N or with Al y1 In x Ga 1-y1N. Here, y1 is preferably greater than 0.05 and x<0.01. The thickness of the first region is, for example, at least 1 nm and at most 5 nm.

[0049] On the side of the first region 2 facing away from the active region 1, the intermediate region 3 follows directly. The intermediate region 3 comprises a first sub-region 3a formed with GaN, a second sub-region 3b formed with In x Ga 1-x N, a third sub-region 3c formed with GaN, a fourth sub-region 3d formed with In x Ga 1-x N, a fifth subregion 3e formed with GaN. The thickness of the subregions is each at least 0.05 nm and at most 5 nm.

[0050] Here, x is preferably greater than 0.01 and less than 0.05. The intermediate region is, in particular, free of aluminum.

[0051] Directly on the side of the intermediate region 3 facing away from the first region 2, the second region 4 is arranged, which is covered with Al y2 Ga 1-y2 N or with Al y2 In x Ga 1-y2 N is formed. Here, x<0.01. Y2 is preferably greater than y1, for example, 0.06 or greater. The thickness of the second region is at least 1 nm and at most 20 nm.

[0052] The first region 2 has an electronic band gap E2 that is larger than the electronic band gap E1 of quantum well 1a and larger than the electronic band gaps E3a, E3b, E3c, E3d, and E3e in intermediate region 3. Subregions 3b and 3d in intermediate region 3 have band gaps E3b and E3d that are smaller than the band gaps E3a, E3c, and E3e in subregions 3a, 3c, and 3e. However, all band gaps in intermediate region 3 are larger than the band gap of quantum well 1a.

[0053] In the second region 4, the semiconductor body has a band gap E4 that is larger than the band gap in all other regions and larger than the band gap E1 in the quantum well.

[0054] The schematic representation of the Fig. Figure 2 shows the intensity of the emitted light of a light-emitting diode with an optoelectronic semiconductor body described here, plotted against the operating time t and normalized to the intensity at time t=0. Curve c is a plot for a semiconductor body described here, whereas curves b and a are comparison curves for semiconductor bodies that do not have the first region 2 and the intermediate region 3. The p-side of the semiconductor body in curve b was produced at a lower growth temperature than the p-side of the semiconductor body in curve a. This leads to reduced diffusion of magnesium into the active region 1 during production. However, after approximately 500 hours of operation, this positive effect is no longer detectable (not shown).

[0055] As can be seen from the graphical representation, the intensity of the generated light for a semiconductor body described here hardly changes over time. This means that the semiconductor body exhibits particularly favorable aging behavior, which can be explained in particular by the improved doping profile with the p-dopant, the improved confinement of charge carriers in the active region, and the reduced diffusion of dopant into the active region both during production and during operation.

[0056] The Fig.Figure 3 shows a schematic representation of a light-emitting diode with a semiconductor body 10 described here. In addition to the described regions, the light-emitting diode comprises an n-conducting region, which is electrically contacted, for example, via the first connection point 11. Located on the opposite side of the semiconductor body 10 is the second connection point 12, via which the semiconductor body is connected, for example, on the p-side.

[0057] During operation, the light-emitting diode generates electromagnetic radiation with a peak wavelength of less than 480 nm, in particular less than 400 nm. It has been shown that, due to the improved confinement of charge carriers in the active region, the use of the semiconductor body described here for generating UV radiation, in particular UVA radiation, is particularly advantageous. The light-emitting diode is then a UV-radiation-emitting light-emitting diode.

[0058] The semiconductor bodies and light-emitting diodes described here are characterized in particular by the following advantages: The semiconductor body exhibits greater tolerance to temperature fluctuations during the fabrication of the p-doped side of the semiconductor body, as the described regions effectively suppress diffusion of the p-dopant into the active region. This reduces the probability of diffusion of the p-dopant into the active region.

[0059] Furthermore, hole injection is improved in a semiconductor body described here compared to a semiconductor body without the regions described here. The outflow of electrons from the active region is also significantly suppressed for an active region with a low indium concentration, such as is used in particular for generating UV radiation, due to the regions of the semiconductor body described here.

Claims

[1] Optoelectronic semiconductor body (10) with - an active region (1) comprising a quantum well (1a) which is designed to generate electromagnetic radiation, - a first region (2) designed to prevent the passage of charge carriers from the active region (1), - a second region (4) which is designed to prevent the passage of charge carriers from the active region (1), wherein - the semiconductor body (10) is based on a nitride compound semiconductor material, - the first region (2) directly borders on the p-side of the active region (1), - the second region (4) is arranged on a side of the first region (2) facing away from the active region (1), - the first region (2) has an electronic band gap (E2) which is larger than an electronic band gap (E1) of the quantum well (1a) and smaller than or equal to an electronic band gap (E4) of the second region (4), - the first area (2) and the second area (4) contain aluminum, - an intermediate region (3) is arranged between the first region (2) and the second region (4), wherein the intermediate region (3) has an electronic band gap (E3a, E3b, E3c, E3d, E3e) which is larger than the electronic band gap (E1) of the quantum well (1a) and which is smaller than the electronic band gaps (E2) of the first region (2) and the second region (4), wherein the intermediate region (3) is at least partially free of aluminum, - the intermediate region (3) has at least two subregions (3a, 3b, 3c, 3d, 3e) which differ from one another in their material composition and their electronic band gap, - the first region (2) and the intermediate region (3) are n-doped, and - the second region (4) is p-doped. [2] Optoelectronic semiconductor body (10) according to the preceding claim, wherein at least one of the subregions (3a, 3b, 3c, 3d, 3e) is free of aluminum. [3] Optoelectronic semiconductor body (10) according to one of the preceding claims, in which the intermediate region (3) directly borders on the first region (2) and directly on the second region (4). [4] Optoelectronic semiconductor body (10) according to one of the preceding claims, in which directly adjacent subregions (3a, 3b, 3c, 3d, 3e) differ from one another with regard to their band gap. [5] Optoelectronic semiconductor body (10) according to one of the preceding claims, wherein the second region (4) has an aluminum concentration which is greater than the aluminum concentration in the first region (2). [6] Light emitting diode with - an optoelectronic semiconductor body (10) according to one of the preceding claims, and - electrical connection points (11, 12) for contacting the optoelectronic semiconductor body (10), wherein - the light-emitting diode is designed to emit electromagnetic radiation with a peak wavelength of less than 480 nm, in particular less than 400 nm.

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