Optoelectronic device and method of manufacturing optoelectronic device

Abstract

The invention relates to a method for processing an optoelectronic device, comprising the steps of: depositing a first layer having a first dopant concentration of a first dopant type; an active region is deposited on the first layer and a second layer having a silicon dopant concentration of a silicon dopant type is deposited on the active region. The step of depositing the active region comprises the following steps: depositing a plurality of alternating barrier layers and quantum well layers, the barrier layers comprising Inx (GayAl1-y) 1-xN, the quantum well layers comprising Inx (GayAl1-y) 1-xN, the aluminum content in the barrier layers being higher than the aluminum content in the quantum well layers; and during deposition of the barrier layer material, doping the barrier layers with silicon such that a subset of the plurality of barrier layers includes a higher silicon dopant concentration than the remaining barrier layers.

Description

[0001] The present invention relates to a method for processing an optoelectronic device and an optoelectronic device. Background Art

[0002] Optoelectronic devices (and in particular, μ-LEDs with dimensions less than 50 μm) typically use a multi-quantum well structure as the active layer for generating photons through charge carrier recombination. Such a multi-quantum well structure comprises multiple alternating quantum well layers and barrier layers. The difference between quantum well layers and barrier layers lies in their band gap, which in turn depends on the material composition. More specifically, quantum well layers have a smaller band gap than barrier layers.

[0003] In ternary or quaternary semiconductors based on nitride material systems (such as InGaN or InGaAlN), such a bandgap difference between the quantum well layer and the barrier layer is achieved by varying the aluminum content between the corresponding layers. A higher aluminum content generally results in a higher bandgap in the barrier layer, thereby trapping charge carriers within the quantum well layer.

[0004] It has been discovered that by doping the barrier layer, the operating voltage, or forward voltage Vf, at a given current can be reduced. For high-efficiency InGaN optoelectronic devices, silicon or silicon is used as a dopant in the barrier layer (typically the barrier layer and quantum well layer are undoped). Silicon doping in the quantum barrier layer results in a lower operating voltage Vf and a reduced polarization field. Both aspects enhance the optical output power and efficiency of the device and are generally desirable.

[0005] However, doping the quantum barrier layer increases the parasitic capacitance in the pn junction. High capacitance leads to a longer delay in the on or off operation because the charge carriers caused by the dopant must be compensated. It has been found that the capacitance increases not only in proportion to silicon doping, but also in proportion to magnesium (Mg) doping, the latter used for p-doping. Therefore, although silicon doping in the quantum barrier layer is desirable for lower operating voltage and higher output efficiency, the switching speed is reduced due to the higher capacitance. Therefore, high switching speed while maintaining low operating voltage is a desirable goal.

[0006] Therefore, an object of the present application is to reduce the total capacitance in μ-LEDs based on III-V optoelectronic devices, thereby increasing the switching speed without significantly reducing the efficiency performance. Summary of the Invention

[0007] This and other objects are solved by the subject matter of the independent claims. Characteristics and further aspects of the proposed principle are outlined in the dependent claims.

[0008] It has been observed that silicon doping in the quantum well barrier reduces the forward voltage due to the hole transport blocking effect of the doped quantum barrier layer. While this may have a useful effect in reducing the operating voltage, it has also been observed that electroluminescence decreases with increasing silicon doping in the quantum barrier layer.

[0009] The inventors realized that in order to operate an optoelectronic device, any charge in the depletion region or active region (or part thereof) (i.e., the plurality of quantum well layers and quantum barrier layers) must be removed by pushing free charge carriers into the depletion region. When the voltage that pushes the free charge carriers disappears, these carriers leave the region and then move back to the current-voltage source. This process never results in light generation, but rather corresponds to a "turn-on delay" in LED operation. The inventors now aim to reduce this space charge caused by doping without reducing the benefits of such doping.

[0010] To this end, the inventors have proposed an improved method for processing micro-LEDs, or more generally, optoelectronic devices. Although the proposed principles are implemented for optoelectronic devices having an edge length of less than 100 μm (commonly referred to as μLEDs) and down to 5 μm or even less, the proposed method is not limited to such small devices. The method includes depositing a first layer having a first dopant concentration of a first dopant type and a second layer having a silicon dopant concentration of a silicon dopant type on an active region, as further described in more detail below.

[0011] In this regard, the first dopant type corresponds to one of an n-dopant or a p-dopant, and the silicon dopant type corresponds to one of a p-dopant and an n-dopant. Non-limiting examples of dopant materials that provide n-doping in III-V semiconductor materials such as GaN, InGaN, or InGaAlN include Te, Ge, or Si, while p-doping can be achieved by implanting Sn or Mg. For the purposes of this application, the first dopant type is expressed as corresponding to the n-doping type and the second doping type is expressed as corresponding to the p-doping type. However, the principles presented are not limited to this particular definition; rather, the dopant types described herein can be interchanged unless otherwise stated.

[0012] The first layer and the second layer can include a constant doping profile, but can also have multiple sublayers with varying dopant concentrations. In some aspects, the first layer and / or the second layer each include an undoped sublayer adjacent to the active area between the sublayers. Thus, the sublayers can act as dopant diffusion barriers to prevent dopants from the first layer and / or the second layer from undesirably diffusing into the active area. Some additional sublayers of the first layer and / or the second layer can include increased doping concentrations, thereby forming current distribution and / or current injection layers. Furthermore, in some aspects of the proposed principles, the sublayers of the first layer and / or the second layer opposite the active area are configured as contact layers.

[0013] As outlined in some aspects, the active region is deposited between the first layer and the second layer. The active layer comprises a multiple quantum well structure having a plurality of alternating barrier layers and quantum well layers. During the deposition of the alternating barrier layers and quantum well layers, the aluminum content of the deposited semiconductor material is varied. More specifically, depositing the plurality of alternating barrier layers comprises depositing In x (Ga y Al 1-y ) 1-x N layer, where x and y are parameters in the range [0:1] and x+y=1. Therefore, some gallium is replaced by aluminum, and the amount of replacement can be between 0 and 1, resulting in In x Ga 1-x N (equal to zero for aluminum content) and In x Al 1-x N (equal to 100% for aluminum and no Ga). Typically, the aluminum content in the barrier layer is higher than 0.1 and can range from 0.15 to 0.40 for blue LEDs. In UV (ultraviolet) LED applications, an Al content of 0.4 or more is more preferred. In general, the aluminum content in the barrier layer is greater than that in the adjacent quantum well layer. This can be achieved by varying the concentration of the aluminum precursor during the deposition of the active region material.

[0014] The increased concentration of aluminum in the barrier layer increases the band gap. According to the proposed principle, during the deposition of the barrier layer material for the plurality of barrier layers, the barrier layers are doped with silicon. However, the doping is not constant, but rather results in a subset of the plurality of barrier layers having a higher silicon dopant concentration than the remaining barrier layers. In other words, the silicon dopant concentration varies during the deposition of the plurality of barrier layers, resulting in some of the deposited barrier layers having a higher silicon concentration than the remaining barrier layers.

[0015] It has been found that varying the silicon concentration with increased dopant concentrations in only some of the barrier layers results in a reduced forward voltage compared to conventional devices, while also reducing the total capacitance. In other words, for a given silicon concentration in a conventional device, the same specific forward voltage can be achieved with a reduced silicon concentration according to the proposed principles, i.e., by varying the concentration in the barrier layers, thereby increasing the silicon concentration in several barrier layers. The reduced total silicon dopant concentration in the barrier layers results in a reduced turn-on delay (and, therefore, an increase in switching time) compared to conventional devices with the same or very similar forward voltage.

[0016] In fact, it has been observed that a specific configuration of the silicon concentration in the barrier layer reduces the forward voltage at a reference voltage, achieved by a uniformly distributed silicon configuration across the barrier layer but with a generally larger amount of silicon dopant deposited within the active region. Thus, it is possible to reduce the excess silicon dopant while surprisingly maintaining a reduced forward voltage and achieving higher switching speeds for the device.

[0017] In this regard, the expression "uniformly distributed concentration across the barrier layers" refers to a distribution in which each barrier layer contains approximately the same amount of silicon dopant, even though the dopant may be unevenly deposited within each respective barrier layer. Similarly, the expression "average" refers to the total amount of silicon dopant across multiple barrier layers, rather than the distribution of the silicon dopant within the barrier layers. According to the proposed principles, the distribution of the silicon dopant varies across the barrier layers, with the average silicon concentration being less than that in conventional devices and the forward voltage being the same or similar.

[0018] For example, in some cases, the average silicon dopant concentration is less than 40% (and more particularly less than 30%) of the reference silicon dopant concentration. However, the silicon dopant profile is not constant, but rather a subset of the barrier layers is deposited with a higher silicon concentration than the remaining barrier layers. Thus, the step of doping the barrier layers includes doping the plurality of barrier layers during respective depositions of the barrier layer material, wherein the dopant concentration is increased during deposition of the subset of the plurality of barrier layers.

[0019] In some aspects, it has been observed that the forward voltage and switching time depend on the location of the higher silicon dopant concentration within the active region and the location of the subset of the plurality of barrier layers within the active region. In some aspects, the subset of the plurality of barrier layers is a subsequent barrier layer. In other words, the barrier layers corresponding to the subset of barrier layers are not distributed along the plurality of barrier layers, but rather form a barrier layer group, each barrier layer in the barrier layer group having a higher silicon concentration than other barrier layers in the plurality of barrier layers.

[0020] In some aspects, the subset or group of barrier layers having a higher concentration is closer to one of the first layer and the second layer. In some aspects, the group of barrier layers is substantially located in the center of the plurality of barrier layers. It has been found that if the subset of barrier layers having a higher silicon concentration is arranged to one of the p-doped side and the n-doped side, the forward voltage is generally lower (or at least not significantly increased compared to a reference voltage given by a reference concentration of silicon dopants). In some aspects, the subset of barrier layers is adjacent to the n-doped side of the optoelectronic device.

[0021] In some other aspects, the barrier layers corresponding to a subset of the plurality of barrier layers are distributed across the active area. In some aspects, the barrier layers corresponding to the subset with a higher silicon concentration are alternated with the barrier layers with a lower concentration. For example, in some aspects, every third barrier layer in the plurality of barrier layers can correspond to a subset of the plurality of barrier layers. It has been found that a higher dopant concentration in the first barrier layer (adjacent to one of the p-doped side and the n-doped side, respectively) and an overall reduced dopant concentration in the remaining barrier layers compared to a reference concentration can result in maintaining a forward voltage. Therefore, in such a configuration, the total silicon concentration can be reduced compared to a reference concentration.

[0022] Some aspects relate to a comparison of the amount of barrier layers in a subset of the plurality of barrier layers to the total amount of barrier layers. In some aspects, the number of barrier layers in the subset of the plurality of barrier layers is approximately 15% to 45% of the total number of barrier layers, and particularly between 25% and 35% of the total number of barrier layers. In some aspects, approximately 1 / 3 of the barrier layers (e.g., 3 barrier layers out of 10 barrier layers) contain an increased silicon dopant concentration compared to the remaining barrier layers. As previously mentioned, at least one of such barrier layers can be adjacent to one of a p-doped side and an n-doped side. Typically, the number of barrier layers in the subset of the plurality of barrier layers is less than the number of the remaining barrier layers (e.g., not part of the subset).

[0023] Some aspects relate to the amount of total silicon concentration in optoelectronic devices according to the proposed principles and methods for processing such devices. In some aspects, the silicon dopant concentration in a subset of the plurality of barrier layers is greater than 50% of the total dopant concentration in the plurality of barrier layers. In some aspects, the total amount of silicon dopants in the subset of the plurality of barrier layers can be between 50% and 80% of the total amount of silicon dopants and particularly in the range of between 60% and 70%. In some aspects, the dopant concentration in the subset of the plurality of barrier layers is greater than 55% and particularly greater than 60% of the total dopant concentration in the plurality of layers. Thus, the remaining barrier layers can contain between 35% and 50% of the total amount of silicon dopants.

[0024] In some cases, the silicon dopant is thus concentrated in a small number of barrier layers, for example, one-third of the total number of barrier layers, but the amount of silicon dopant totals approximately 60% to 75% of the total amount of deposited Si. Furthermore, it should be noted that the total amount of silicon dopant in the multiple barrier layers has been reduced compared to the reference amount in conventional devices. In some cases, the total amount of silicon dopant is approximately between 25% and 40% of the reference amount. In other words, and in accordance with the proposed principles, approximately the same forward voltage can be achieved even with an amount of silicon dopant less than half of the amount previously used.

[0025] Some aspects relate to the deposition of dopants during the deposition of the barrier material. In some aspects, the step of doping the barrier layer during the deposition of the barrier layer material includes depositing the dopant material after depositing the corresponding portion of the barrier layer and / or completing the deposition of the dopant material while continuing to deposit the barrier layer material. Thus, the silicon dopant is unevenly distributed across the barrier layer. Instead, silicon can be doped into the barrier layer material after some barrier layer material has been deposited. In some cases, the amount of silicon doping can vary even during the deposition of the barrier layer material. For example, in some cases, silicon doping can occur only during a time interval that is shorter than the duration used to deposit the barrier layer material, and the time interval can begin after the deposition of the barrier layer material has begun and / or can stop before the deposition of the barrier layer material has stopped.

[0026] In some cases, the doping profiles in the plurality of barrier layers can be the same despite the increased concentration of dopants during deposition of the subset of barrier layers. In some other cases, the doping profiles in the subset of barrier layers can be different compared to other barrier layers in the plurality of barrier layers.

[0027] In this aspect, the step of doping the barrier layers with silicon includes doping alternating barrier layers, particularly every third barrier layer, with a greater amount of silicon dopant. In some aspects, only every third or fourth barrier layer is doped with a greater amount of silicon dopant than the other barrier layers.

[0028] In some aspects, the silicon dopant concentration within a subset of the plurality of barrier layers is between 2e17 1 / cm 3 to 5e18 1 / cm 3 In some aspects, the silicon concentration in a subset of the plurality of barrier layers does not exceed a concentration of about 1e19 1 / cm3.

[0029] In view of the above ratio of more than 50% of the total amount of silicon dopants while leaving only about 33% highly doped, the average amount of silicon in the active area can be 5e16 1 / cm 3 to 2e18 1 / cm 3 In some cases, the average dopant concentration within the plurality of barrier layers is between 1e17 1 / cm 3 to 1e181 / cm 3 In some cases, the silicon dopant concentration in the barrier layer that is not part of the subset is less than 1e18 1 / cm 3 and specifically less than 5e17 1 / cm 3 In some aspects, the dopant concentration within a subset of the plurality of barrier layers can be at least twice as great as the dopant concentration within the remaining barrier layers (that are not part of the subset).

[0030] In addition to silicon doping during the deposition of the barrier layer of the active region, dopants of different doping types may also be introduced during the deposition of the active region layer. In this regard, dopants of different doping types include, but are not limited to, p-type dopants such as Mg. In this case, it is assumed that silicon as a dopant is similar to an n-type dopant. Therefore, in some aspects, at least a portion of the active region is doped with a silicon dopant such as Mg having a doping type different from that of Si. In this regard, it may also be attempted to reduce the total concentration of Mg or to distribute the dopants non-uniformly to achieve a reduction in charge capacitance, thereby increasing switching speed.

[0031] Another aspect relates to optoelectronic devices, and in particular to μLEDs having a length of less than 100 μm and in particular less than 50 μm. In some aspects, the optoelectronic device includes a first layer having a first dopant concentration of a first dopant type and a second layer on the active area, the second layer having a silicon dopant concentration of a silicon dopant type. The active area is arranged between the first layer and the second layer, respectively. Similar to the method mentioned above, the first layer and the second layer may include multiple sublayers, including but not limited to current injection layers or current distribution layers. Some highly doped sublayers are part of the first layer and the second layer, respectively, and may form contact layers for depositing metal contacts thereon.

[0032] In some aspects, each of the first and second layers can include an undoped cladding layer adjacent to the active region. The cladding layer can include, for example, a different material having a different band gap than the active region and / or other sublayers of the first and second layers. The cladding layer can act as a diffusion barrier to prevent undesired diffusion of dopants from the first or second layer into the active region.

[0033] According to the proposed principle, the active region comprises a plurality of alternating barrier layers and quantum well layers, the barrier layers comprising In x (Ga y Al 1- y) 1-x N, the quantum well layer includes In x (Ga y Al 1- y) 1-x N, where x and y are parameters in the interval [0:1] and x+y=1, and wherein the aluminum content in the barrier layer is higher than the aluminum content in the quantum well layer. Typically, the aluminum content in the barrier layer is higher than 0.4 and may be in the range of 0.45 to 0.75. A subset of the plurality of barrier layers includes a higher doping concentration, particularly a higher silicon doping, than the remaining barrier layers.

[0034] Although the silicon dopant level varies within the barrier layer, the total amount of silicon dopant is reduced relative to the reference doping level that results in a specific forward voltage level. Furthermore, even at lower dopant levels, the forward voltage remains approximately the same. This is due to non-uniformity across the active region, with some barrier layers having greater dopant concentrations than others. However, the reduced total dopant level reduces the parasitic capacitance of the active region and, therefore, significantly reduces turn-on delay.

[0035] Thus, the proposed optoelectronic device achieves similar electrical and optical efficiencies with reduced doping levels in the active region and increased switching speeds. In some cases, subsets of multiple barrier layers are arranged one after another. Thus, barrier layers with increasing doping levels follow one another. Furthermore, the subset of barrier layers can be positioned adjacent to the first layer, or adjacent to a layer having the same doping type as the subset of barrier layers.

[0036] In some alternative aspects, barrier layers corresponding to a subset of the plurality of barrier layers alternate with barrier layers that do not correspond to the subset of the plurality of barrier layers. In this regard, it is possible that there is first a change between barrier layers corresponding to a subset of the plurality of barrier layers, alternating with barrier layers that do not correspond to the subset, followed by another number of barrier layers that do not correspond to the subset.

[0037] In some aspects, the number of barrier layers corresponding to the subset of barrier layers is less than the number of barrier layers that do not correspond to the subset of barrier layers. In other words, there are more barrier layers with a smaller dopant concentration than barrier layers with a larger doping concentration, and the barrier layers with the larger doping concentration correspond to the subset. In this regard, it can be noted that in some aspects, the amount of barrier layers in the subset of the plurality of barrier layers is approximately between 15% and 45% of the total amount of the plurality of barrier layers, and in particular, between 25% and 35%. In other words, there are approximately 2 to 4 times more barrier layers with a reduced doping amount than there are barrier layers with an increased doping amount.

[0038] Some aspects relate to the thickness of the barrier layer. In some aspects, the thickness of the barrier layer can be between 5 nm and 80 nm, but is typically greater than 10 nm and less than 60 nm. However, the area of the barrier layer doped with the barrier layer material can vary and, in particular, be less than the thickness of the barrier layer itself. In other words, the barrier layer may not be fully doped, but rather the dopant may follow a specific distribution across the thickness of the barrier layer. In this regard, it is possible that the dopant is slightly diffused within the barrier layer so that a clear boundary cannot be established.

[0039] Still in some aspects, the thickness of the barrier layer in a subset of the barrier layers can be greater than the thickness of the doped regions within the barrier layer. Thus, the barrier layer may not be fully doped, but rather the dopant within the barrier layer may follow a doping profile. In some aspects, the doped regions are not adjacent to the quantum well layer adjacent to the barrier layer. In another aspect, there are regions of the barrier layer adjacent to the quantum well layer doped with Si.

[0040] In this regard, it is understood by those skilled in the art that the barrier layers within a subset do not need to have the same dopant concentration, nor do the barrier layers that do not correspond to a subset need to have the same dopant concentration. Therefore, the dopant concentration of different barrier layers can be varied, and for example, three subsets of barrier layers can be implemented, each having a different dopant concentration.

[0041] In some aspects, the dopant concentration in the subset of the plurality of barrier layers is greater than 50% and particularly greater than 55% of the total dopant concentration in the plurality of barrier layers. Thus, the majority of silicon dopants within the active region are concentrated within the subset of the plurality of barrier layers. Because the number of barrier layers within the subset is less than the number of barrier layers not corresponding to the subset, the majority of silicon dopants are concentrated in a small portion of the active region.

[0042] In some other aspects, the dopant concentration in the barrier layers of a subset of the plurality of barrier layers varies along the thickness of the barrier layers, particularly increasing toward the quantum well layers adjacent to the barrier layers. Thus, the distribution of dopants within or outside the barrier layers of the subset can vary. For example, the dopant can be concentrated closer to the quantum well layers or adjacent to the quantum well layers.

[0043] In some further aspects, the dopant concentration within a subset of the plurality of barrier layers is between 2e17 1 / cm 3 to 5e18 1 / cm 3 Although the dopant concentration within the subset is typically less than 1e19 1 / cm3, the dopant concentration within the subset can be at least twice as great as the dopant concentration in the remaining barrier layers (that are not part of the subset). In alternative embodiments, the dopant concentration within the subset can be at least twice as great as the average dopant concentration within the active region. In some aspects, the average dopant concentration within the plurality of barrier layers is between 1e17 1 / cm3 and 1e17 1 / cm3. 3 to 1e18 1 / cm 3 within the range between.

[0044] In some aspects, the optoelectronic device further comprises a silicon dopant within the active region, the silicon dopant comprising a different doping type. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Further aspects and embodiments according to the proposed principles will become apparent with respect to the various embodiments and examples described in detail with reference to the accompanying drawings, in which:

[0046] Figure 1 Implementations of optoelectronic devices implementing some aspects of the proposed principles are shown;

[0047] Figure 2 A first embodiment of an active region implementing some aspects of the proposed principles is shown;

[0048] Figure 3 shows a second embodiment of an active region according to some aspects of the proposed principles;

[0049] Figure 4 shows a third embodiment of an active region according to some aspects of the proposed principles;

[0050] Figure 5 A fourth embodiment of an active region implementing some aspects of the proposed principles is shown;

[0051] Figure 6 shows a fifth embodiment of an active region implementing some further aspects of the proposed principles;

[0052] Figure 7 Another embodiment of an active region is shown to illustrate some aspects of the proposed principles;

[0053] Figure 8 A graph showing dopant concentration across an active region according to some aspects of the proposed principles;

[0054] Figure 9 A graph showing the deviation of the forward voltage of an optoelectronic device versus the relative doping concentration within the active region is shown. DETAILED DESCRIPTION

[0055] The following embodiments and examples disclose various aspects and combinations thereof according to the proposed principles. The embodiments and examples are not always drawn to scale. In particular, although the expression optoelectronic devices is used in this application, it is not limited to large devices. In particular, the expression should cover so-called μ-LEDs, which typically include devices with a wavelength of less than 3000 μm. 2 And even less than 1000μm 2Small dimensions or lengths down to a few μm. Similarly, different elements may be shown exaggerated or reduced in size to emphasize various aspects. It goes without saying that various aspects of the embodiments and examples shown in the drawings can be easily combined with one another without conflicting with the principles of the present invention. Some aspects show regular structures or forms. It should be noted that in practice, slight differences and deviations from the ideal form may occur, but this does not conflict with the inventive concept.

[0056] Furthermore, the various figures and aspects are not necessarily shown to exact scale, nor are the proportions between the various elements necessarily substantially correct. Some aspects are highlighted by enlarging them. However, terms such as "above," "above," "below," "below," "larger," "smaller," and the like are intended to represent accurate representations of the elements in the figures. Therefore, such relationships between the elements can be inferred based on the figures.

[0057] Figure 1 A cross-section of an optoelectronic device, configured to achieve an improved active area for a single μLED according to the proposed principles, is shown. The optoelectronic device 1 comprises a layer stack 2, in particular a semiconductor layer stack based on a nitride material system, deposited on a temporary carrier substrate 11. More specifically, the layer stack 2 deposited on the carrier substrate comprises a first charge carrier transport layer 3 of a first doping type, a second charge carrier transport layer 4 of a second doping type, and an active area 5 arranged between the first and second charge carrier transport layers.

[0058] In this embodiment, the layer stack includes a top surface 2a and an inclined side surface 2b adjacent to the top surface, wherein the side surface is inclined at an angle α relative to the normal N of the top surface 2a. The angle α can be based on the etching process discussed below, but also depends on the crystal orientation of the material used. The angle can also vary along the sidewall, with various angles possible.

[0059] Referring now in more detail to the layer stack 2, the stack comprises a first charge carrier transport layer corresponding to a first layer of a first doping type. Figure 1 As shown in FIG, the first layer 3 comprises one or several n-doped sublayers 3b to 3d deposited on a buffer layer 3a. The buffer layer 3a is adjacent to a carrier layer 11. The carrier layer 11 may comprise, for example, Al2O3, on which the buffer layer 3a, which is an n-doped GaN or AlGaN layer, and the subsequent layers 3b, 3c, and 3d are deposited. The buffer layer 3a may be removed later.

[0060] Several doped and / or undoped sublayers 3b, 3c, and 3d are arranged on top of layer 3a, acting as charge distribution layers, charge transport layers, or providing other and different functions. Sublayer 3d comprises, for example, InGaAlN and is positioned directly adjacent to the active region 5. Layer 3d is undoped and may comprise a thickness of only a few tens of nm. Layer 3d acts as a cladding layer for the active region and prevents undesired diffusion of dopants from sublayers 3b and 3c into the active region 5.

[0061] The active region 5 comprises a multi-quantum well structure, which will be described in more detail later. A similar cladding layer 4c is then arranged on top of the active region 5, wherein the cladding layer 4c forms a sublayer of the second charge carrier transport layer 4. Similar to the first layer 3, the second charge carrier transport layer 4 comprises several p-doped layers 4a, 4b and one or several undoped barrier layers 4c adjacent to the active region 5. As far as the active layer 5 is concerned, both layers 3d and 4c can comprise materials of the same or very similar composition. In the given example, both comprise undoped InGaAlN material.

[0062] The optoelectronic device 1 further comprises a sloping sidewall extending from the first charge transport layer 3 (more specifically, sublayer 3d) to the vicinity of sublayer 4b, which is part of the (p-doped) second charge carrier transport layer. The top sublayer 4b has a smaller area than the other sublayers 4c, the active region 5, and / or the first charge carrier transport layer. In other words, the sloping surface, which forms an angle α with respect to the normal N, is less than 90°.

[0063] The sidewalls 2b of the layer stack are covered by layer 6a, which is overgrown during device processing and exposes at least part of the top surface 2a. The material of layer 6a is selected to provide a larger bandgap than the active area 5, but optionally also to provide a larger bandgap than the adjacent layers 4c, 4b and 3d of the first and second charge transport layers. In some aspects, layer 6a can be an insulating layer. The larger bandgap of layer 6a creates an electrical barrier, thereby preventing charge carriers injected into the active area from diffusing to the sidewalls and recombining in a non-radiative manner. Although this aspect may not be highly relevant here due to the material system and its short diffusion length, layer 6a still protects the underlying layer stack from oxygen, dust or possible damage.

[0064] The material of the highly p-doped contact sublayer 4a is deposited on top of the overgrown insulating layer 6a and the sublayer 4b, the contact sublayer 4a forming part of the second charge carrier transport layer 4. Finally, a metal contact 7 is applied to the sublayer 4a. This structure can be varied, in particular by removing the material of the insulating layer 2b on the sidewalls or by protecting the insulating material from overgrowth by the sublayer 4a.

[0065] The present structure can be processed by providing a carrier substrate 11 and then depositing the corresponding layer stack. First, a buffer layer 3a is deposited so that a smooth and preferably defect-free or defect-reduced surface is created. This surface is used to deposit the further sublayers of the first layer 3, which, with the exception of the cladding sublayer 3d, are n-doped. The semiconductor materials used for the sublayers can vary depending on the desired functionality, but typically include one or more layers of InGaN or InGaAlN material with varying Al contents. A typical material for doping is silicon, which acts as an n-dopant for InGaN / InGaAlN-based material systems.

[0066] Then, a multi-quantum well structure is deposited in the active area 5, as will be further described in more detail below. A further undoped cladding sublayer 4c is deposited on the finished active area, followed by a p-doped charge carrier transport layer. In a next step, a structured hard mask is applied, in which surface areas of layer 4b are exposed. These exposed surface areas are etched to form a Figure 1 The exposed side edges of the mesa structures are covered by the material of layer 6a and the rest of the hard mask is removed. The remaining sub-layers of the second layer 4 are then deposited.

[0067] A number of various embodiments can be realized for the processing method according to the proposed principle, the presently indicated embodiments being non-limiting examples.

[0068] Reference is now made to the deposition of the active region, its structure and its characteristics. Figure 1 In the optoelectronic device or μLED shown in , the charge in the active area must be removed by pushing the free carriers into the depletion region, and more specifically, the charge in the depletion part of the active area. This process occurs when the device is turned on and when the device is turned off. Therefore, part of the charge carriers is used to deplete (de-populate) or refill (re-populate) the active area and will therefore not participate in any light generation. The resulting capacitance in the pn junction (i.e. the active area) depends on the amount of such carriers, which can be changed by doping the active area with, for example, silicon or magnesium. In order to reduce the total capacitance of the pn junction, the amount of dopant within the active area can be reduced, resulting in higher switching speeds.

[0069] The proposed principle aims to minimize the capacitance within the region without sacrificing the reduced threshold voltage U caused by doping in the active region. f The total capacitance within the active region corresponds to C = Q / V, where Q is the available charge carriers within the region and is given by:

[0070]

[0071] And n A and nD are the donor concentration and the acceptor concentration, respectively. For this material system, magnesium Mg acts as an acceptor (p-dopant) and silicon acts as a donor (n-dopant). Reducing the charge ΔQ can be achieved by reducing the donor concentration and / or the acceptor concentration.

[0072] Figure 9 The variation of the space charge with Si doping at 0 V is shown, showing the square root dependence on the cumulative Si doping. The cumulative Si doping corresponds to the average Si doping concentration. As can be seen, in the case of higher Si dopant concentrations (e.g. close to 100% as a reference level), an increased charging voltage up to 1.8 V can be observed. The curve itself follows a square root dependence. On the other hand, a smaller average Si doping leads to an increase in the operating voltage. The table below shows the forward voltage ΔU f and the change in quantum efficiency Ie relative to the 80% average doping level reference.

[0073] Average Si ΔUf Ie% 1 80.0％ refer to 100.0％ 2 40.0％ +20mV 100.7％ 3 30.4％ +35mV 101.3％ 4 25.0％ +45mV 101.0％ 5 20.0％ +85mV 99.2％

[0074] When the amount of Si doping is reduced (eg, to about half of the reference level), the forward voltage U f has increased by 20 mV and increases further with decreasing silicon doping concentration across the active region. Although the quantum efficiency may increase slightly (possibly due to a reduction in the number of non-radiative recombination centers), the forward voltage U f The increase leads to some disadvantages.

[0075] Therefore, an improved doping scheme within the active region and more specifically within the barrier layers of the multiple quantum well structure of the active region is proposed.

[0076] Figures 2 to 5 Various embodiments of a multi-quantum well structure according to the proposed principle are shown, each having a plurality of alternating quantum well layers and quantum barrier layers and a tuned doping profile within the quantum barrier layers.

[0077] The doping profile is considered from a reference doping level used in conventional devices, which corresponds to a reference level of 100% silicon dopant concentration as shown above in Table 1. Such a dopant level results in a certain quantum efficiency, but also in a certain forward voltage, which is lower compared to an undoped active region.

[0078] exist Figures 2 to 5 In the corresponding embodiment of FIG, various principles and options for different doping levels are shown, which lead to reduced capacitance in the active area and similar forward voltage U f , although the exact amount and exact reduction in total silicon doping concentration within the active region may vary and depend on the actual implementation.

[0079] Specifically, as further outlined below, the total silicon concentration is about 30% of the reference level given in Table 1. When considering conventional devices, the reduction results in an average silicon level being reduced to about 30%, but its distribution is substantially equal across the active region. As shown in Table 1, such a method results in a significant increase in the forward voltage U f .

[0080] However, in the proposed embodiment, the voltage level can be substantially maintained at a reference level comparable to an 80% average doped silicon as outlined in Table 1, while increasing the quantum efficiency and reducing the total capacitance.

[0081] As a result of the reduction in the average silicon dopant concentration, the capacitance is reduced, leading to an increase in the switching speed while maintaining the same forward voltage U f as in a conventional device with 100% reference level silicon doping. In addition to the increased switching speed, the quantum efficiency may increase slightly due to the reduced concentration of non-radiative recombination centers.

[0082] The right side of each embodiment ( Figures 2 to 5 ) shows an active region having a plurality of quantum barrier layers QB and quantum well layers QW, the plurality of quantum barrier layers QB and quantum well layers QW being stacked on top of each other between a cladding layer CL1 and a cladding layer CL2 respectively. The cladding layer CL1 and the cladding layer CL2 are undoped and comprise a material system based on ternary or quaternary nitrides. Such a system includes InGaAlN, but is not limited to such an example.

[0083] In this regard, the cladding layers Cl1 and Cl2 of the embodiment have a thickness of a few nanometers and act as diffusion barriers to prevent dopants from entering the active region and the quantum barrier layers respectively from adjacent carrier transport layers (not shown herein), or to prevent dopants from entering the adjacent carrier transport layers from the active region and the quantum barrier layers respectively. Each quantum barrier layer QB includes an aluminum content that is greater than the aluminum content of the adjacent quantum well layer and the cladding layers CL1 and CL2 respectively. Specifically, for blue or other color LEDs, the aluminum content of the quantum barrier layer QB in the active region can be in the range from 0% to 40%, even in the layer for electron blocking on the p side of the LED. For LEDs in the UV range, the Al content can be higher and can be in the range between, for example, 40% to 80% respectively. Thus, the semiconductor material for the quantum barrier layer QB can be In x (Ga y Al l-y ) 1-x N, where 0.5 < y < 1, although even lower values of y are possible.

[0084] The quantum barrier layers QB comprise a thickness of tens of nanometers, for example, in the range of 5 nm to 50 nm, respectively. The quantum well layers QW have similar thicknesses, but include lower levels of aluminum, and in some cases, no aluminum at all (e.g., only In x Ga 1-x By adjusting the indium content of the quantum well layer, the color of the corresponding optoelectronic device can be changed. However, changing the indium content may cause some strain in the crystal structure and should therefore be avoided or at least kept below a certain threshold.

[0085] exist Figures 2 to 5 The silicon doping level relative to the reference doping level of the quantum barrier layer is shown on the left side of the corresponding embodiment presented in FIG. Although there is no silicon doping in the corresponding quantum well layer QW in this embodiment, it should be noted that silicon atoms can diffuse into the quantum well layer QW by diffusion or other means. However, for the purpose of the proposed principles, no intentional silicon doping is performed in the quantum well layer QW.

[0086] Figure 2 A first embodiment is shown in which the first two quantum barrier layers, viewed from the n-doped side, are doped with silicon doping levels comparable to a reference doping level. The remaining three quantum barrier layers QB in this embodiment are doped with significantly lower doping levels compared to the reference doping level, such that the overall average silicon dopant concentration across the active region is approximately 30% of the reference level.

[0087] In this embodiment, a subset of the quantum barrier layers QB includes a significantly higher Si dopant concentration than the remaining quantum barrier layers. The distribution of the silicon doping in the active region is biased towards the n-doped side (with the cladding layer CL1) in the corresponding quantum barrier layer. It has been found that such a bias of the silicon dopant concentration towards the n-doped side maintains the forward voltage level U compared to the aforementioned silicon doping reference level across all quantum barrier layers. f However, according to the proposed principle, the total silicon dopant concentration (or the amount of Si in the active region) is about 30% of the reference level, thereby significantly reducing the capacitance in the active region. The quantum well layers remain essentially undoped, that is, they are not intentionally doped with silicon.

[0088] Figure 3Another embodiment of the active region and the corresponding level of silicon dopant in the quantum barrier layer QB is shown. In this embodiment, only each second quantum barrier layer includes a larger silicon dopant concentration. More specifically, the quantum barrier layer QB adjacent to the cladding layer CL1 and the cladding layer CL2 includes a higher silicon dopant concentration than the quantum barrier layer adjacent thereto. More specifically, in some aspects, the silicon doping of each second quantum barrier layer QB can be set to a low value or even zero, while almost no silicon doping occurs during the deposition of the material of the quantum barrier layer QB. Similar to the previous embodiment, the total level of silicon dopant is approximately 30% compared to the reference level.

[0089] In this particular embodiment, the alternating quantum barrier layers are doped with a relatively large amount of silicon, although even for these more highly doped barrier layers the dopant concentration is slightly below the reference level. Due to the overall low amount of silicon in the quantum barrier layers, a low forward voltage U is still maintained. f And the total active area capacitance is reduced.

[0090] In some other alternative embodiments, the distribution of dopant concentrations is reversed, i.e., Figure 3 In contrast to the embodiment of the present invention, the quantum barrier layer adjacent to the cladding layer can be doped with a smaller concentration of silicon to avoid diffusion of silicon material into the cladding layer. In addition, the dopant concentration within the higher doped quantum barrier layer can be additionally adjusted to different levels.

[0091] exist Figure 4 In another embodiment shown in , the distribution of silicon atoms deposited during the deposition of the corresponding quantum barrier layer is not constant. In this embodiment, the active region again includes a plurality of alternating quantum barrier layers QB and quantum well layers QW. In an embodiment, the concentration of silicon dopants in the quantum barrier layer QB is not constant, but is biased and offset toward the adjacent quantum well layer when viewed from the n-side. More particularly, during the deposition of the quantum barrier layer, a small portion of the quantum barrier layer material is deposited without additional silicon doping. After depositing a few nanometers of the quantum barrier layer material, silicon dopants are added, resulting in doped deposition of the quantum barrier layer material. Silicon doping continues until the deposition of the barrier layer material is completed and the deposition of the quantum well layer material is initiated.

[0092] As Figure 4 In the result shown on the left side of the embodiment, the concentration of the silicon dopant at each initial starting position of the quantum barrier layer is essentially zero or at least very low, but jumps to a level slightly above the reference level after a short distance within the quantum barrier layer.

[0093] Furthermore, the overall deposition of silicon is not equal, but rather similar to Figure 2In an embodiment, only the first few quantum barrier layers are heavily doped with silicon dopants. In this embodiment, when viewed from the n-doped side of the device, the first three quantum barrier layers are heavily doped in corresponding sub-portions of the quantum barrier layers. The remaining two quantum barrier layers closer to the p-side are also doped with silicon, but with a smaller concentration during their respective deposition. More particularly, the heavily doped quantum barrier layers include a silicon concentration that may even be higher than an average reference level, such as Figure 4 However, the total silicon dopant concentration in the quantum barrier layer is about 30% compared to the reference level.

[0094] In this embodiment, about two-thirds of the thickness of each quantum barrier layer is doped with silicon, while the remaining one-third of its thickness adjacent to the quantum well layer or cladding layer CL1 remains undoped. On the other hand, the higher silicon doping side continues to the adjacent quantum well layer or continues to the second cladding layer CL2. In other words, some of the quantum well layers are positioned adjacent to the directly adjacent quantum barrier layer with a high doping concentration and the second quantum barrier layer with a lower doping concentration, respectively. Depending on the diffusion characteristics of silicon within the quantum barrier layer, the resulting structure may be slightly disrupted, resulting in Figure 4 The illustrations in Figure 3 compare different dopant distributions.

[0095] In some further cases, the dopant concentration may vary continuously during the deposition of the quantum barrier layer material, starting from a low level and increasing to a high level above or below a corresponding reference level. Figure 5 Shown in.

[0096] In this embodiment, the first quantum barrier layer, the third quantum barrier layer, and the fifth quantum barrier layer QB are doped with a silicon concentration that starts at a relatively low level and continuously increases to a higher level at about half the thickness of the corresponding quantum barrier layer. During the deposition of the corresponding quantum barrier layer material, the silicon dopant concentration is continuously increased until its upper limit is reached to remain constant during the remaining deposition of the barrier layer. Thus, the silicon doping concentration starts at a low level and continuously increases to above the reference level, remaining constant across a specific thickness of the first quantum barrier layer, the third quantum barrier layer, and the fifth quantum barrier layer. The second quantum barrier layer and the fourth quantum barrier layer are either substantially undoped or at least doped at a concentration of 20% or less compared to the reference level. Similar to the previous embodiment, the total dopant concentration of silicon in the active region is approximately one-third of the reference level.

[0097] Figure 6Yet another embodiment is shown in which one or more quantum barrier layers centrally arranged within the active region remain undoped, while the quantum barrier layers adjacent to the cladding layers Cl1 and Cl2 are doped with a higher concentration of silicon. Thus, in this embodiment, the quantum barrier layer QB having a higher doping scheme is front-biased and back-biased, while the centrally arranged quantum barrier layer is undoped. Of course, the structure can be reversed, in which the quantum barrier layers adjacent to or near the two cladding layers are undoped and the centrally arranged quantum barrier layer is doped with a higher level of silicon concentration. This may be useful for preventing dopants from diffusing into the quantum well layer through the cladding layers and adjacent barrier layers.

[0098] Despite Figures 2 to 6 In the present embodiment, only five quantum barrier layers and quantum well layers are shown for the active region, but it is apparent to technicians that multiple such barrier layers and quantum well layers can be implemented without being limited to the specific number shown in this article.

[0099] However, according to the present invention, a subset of the quantum barrier layers includes a higher silicon dopant concentration than the remaining quantum barrier layers, even though the number of barrier layers corresponding to the subset is less than the number of barrier layers not corresponding to the subset.

[0100] Figure 7 An embodiment is shown in which a subset of the interleaved quantum barrier layers QB on the n-doped side of the active region includes a higher dopant concentration. In this embodiment, the thickness of the quantum well layer QW is slightly less than that of the corresponding quantum barrier layer, although these thicknesses can be adjusted according to the needs of the respective device. Only approximately one-third of the quantum barrier layers QB are actually doped with a significant amount of silicon, while the remaining quantum barrier layers include a significantly lower silicon concentration. The total silicon concentration is between 20% and 30% of the previously mentioned reference level.

[0101] Figure 7 The two figures below the structure illustrate this aspect in more detail. Specifically, when viewed from the n-doped side of the device, the highly doped silicon layer is front-biased, and only the first 30% of the quantum barrier layer includes a higher silicon doping, while the remaining 70% of the quantum barrier layer includes a significantly lower silicon dopant concentration. On the other hand, approximately 60%, 70%, or even 80% of the total silicon dopant concentration is concentrated within that 30% of the quantum barrier layer. In other words, more than 60% of all silicon is typically located within the first 30% of the total thickness of the active region.

[0102] like Figure 7 As shown in , the remaining 20% to 40% of the silicon dopant is distributed across the remaining quantum barrier QB. However, the total amount of silicon dopant is reduced relative to the reference level while maintaining the forward voltage and reducing the total capacitance. Compared to the higher reference level of silicon dopant in conventional devices, the forward voltage U fThe maintenance of is achieved by the non-uniform distribution of silicon dopant concentration in the corresponding barrier layer.

[0103] In this respect, it has been found that doping the first few quantum barrier layers with a higher dopant concentration can lead to not only maintaining the reference voltage U f , and actually slightly lowers the reference voltage while also reducing the active region capacitance. Implementations where the quantum barrier layer adjacent to the p-doped side includes an active region with a higher silicon dopant concentration can result in a forward voltage U close to the reference voltage. f , although the total silicon dopant concentration is about 1 / 3 to 1 / 2 of the reference concentration.

[0104] Figure 8 A SIMS plot of such dopant concentrations for silicon across the active region is shown. From the indicated point P1 (corresponding to the start of the active region at the p-doped side of the optoelectronic device) to the left, the silicon concentration is below 1e17 1 / cm 3 Such a value is close to the measurement limit for silicon as a dopant. Between point P1 and point P2 (i.e., in the active region), the dopant concentration in the corresponding barrier layer is essentially the same and is approximately 1.5e17 1 / cm 3 to 2e17 1 / cm 3 .

[0105] In the last section between points P2 and P3, where the quantum barrier layer with increased dopant concentration is realized, it can be observed that the average dopant concentration increases to about 3e17 1 / cm 3 to 4e171 / cm 3 At approximately point P4 corresponding to the n-doped side of the carrier transport layer, the dopant concentration will further increase from point P3 to approximately 1e18 1 / cm 3 dopant concentration.

[0106] As described in the previous embodiments, silicon doping in the active region of the optoelectronic device can lead to a significant reduction in forward voltage and current. However, due to the biasing of the dopant within the active region, the total amount of silicon doping can be reduced while simultaneously reducing the forward voltage U f The reduction in silicon also reduces capacitance and thus increases switching speed. Thus, reduced capacitance and voltage can be achieved by adjusting different doping ratios across the active region.

[0107] Reference Signs List

[0108] 1 Optoelectronic devices

[0109] 2a Top surface

[0110] 2b Sloping sidewalls

[0111] 3 First floor

[0112] 3a, 3b sublayers

[0113] 3c, 3d sublayers

[0114] 4 Second floor

[0115] Sublayers 4a and 4b

[0116] 4c sublayer

[0117] 5 Active region

[0118] 6a Insulation layer

[0119] 7 Contact layer

[0120] 11 Carrier substrate

[0121] CL1, CL2 coating

[0122] QB quantum barrier layer

[0123] QW quantum well layer.

Claims

1. A method for manufacturing an optoelectronic device, comprising: - depositing a first layer having a first dopant concentration of a first doping type; - depositing an active region on said first layer; - depositing a second layer on the active area, the second layer having a second dopant concentration of a second doping type; The step of depositing the active area includes: - depositing a plurality of alternating barrier layers and quantum well layers, the barrier layers comprising In x (Ga y Al 1-y ) 1-x N, the quantum well layer includes In x (Ga y Al 1-y ) 1-x N, wherein x and y are parameters in the interval [0:1] and x+y=1, and wherein the aluminum content in the barrier layer is higher than the aluminum content in the quantum well layer; - during deposition of the barrier layer material, doping the barrier layers with silicon such that a subset of the plurality of barrier layers comprises a higher silicon dopant concentration than the remaining barrier layers, wherein the barrier layers in the subset are arranged alternatingly with the remaining barrier layers.

2. The method according to claim 1, wherein The step of doping the barrier layers comprises doping the plurality of barrier layers during respective depositions of the barrier layer material, wherein the dopant concentration is increased during deposition of the subset of the plurality of barrier layers.

3. The method according to claim 1 or 2, wherein: The amount of barrier layers in the subset of the plurality of barrier layers is approximately 15% to 45% of the total amount of the plurality of barrier layers, and in particular between 25% and 35% of the total amount of the plurality of barrier layers.

4. A method according to any one of the preceding claims, wherein The dopant concentration in the subset of the plurality of barrier layers is greater than 50% and specifically greater than 55% of the total dopant concentration in the plurality of barrier layers.

5. A method according to any one of the preceding claims, wherein Doping the barrier layer during the deposition of the barrier layer material includes depositing a dopant material after depositing a corresponding portion of the barrier layer and / or completing the deposition of the dopant material while continuing to deposit the barrier layer material.

6. A method according to any one of the preceding claims, wherein The dopant concentration within the subset of the plurality of barrier layers is between 2e17 1 / cm 3 to 5e18 1 / cm 3 and / or The average dopant concentration in the plurality of barrier layers is 1e17 1 / cm 3 to 1e18 1 / cm 3 and / or Wherein the dopant concentration within the subset of the plurality of barrier layers is at least twice an average dopant concentration across the active region.

7. The method according to any one of the preceding claims, further comprising: - doping at least part of the active region with a dopant different from silicon.

8. A photoelectric device comprising: a first layer having a first dopant concentration of a first doping type; - an active region on said first layer; - a second layer on the active area, the second layer having a second dopant concentration of a second doping type; - wherein the active region comprises a plurality of alternating barrier layers and quantum well layers, wherein the barrier layers comprise In x (Ga y Al 1- y) 1-x N, the quantum well layer includes In x (Ga y Al 1- y) 1-x N, wherein x and y are parameters in the interval [0:1] and x+y=1, and wherein the aluminum content in the barrier layer is higher than the aluminum content in the quantum well layer; wherein a subset of the plurality of barrier layers comprises a higher doping concentration, in particular a higher silicon doping concentration, than the remaining barrier layers, wherein the barrier layers of the subset are arranged alternatingly with the remaining barrier layers.

9. The optoelectronic device according to claim 8, wherein the number of barrier layers corresponding to the subset of barrier layers is less than the number of barrier layers not corresponding to the subset of barrier layers; and / or The amount of the barrier layers in the subset of the plurality of barrier layers is approximately 15% to 45% of the total amount of the plurality of barrier layers, and particularly between 25% and 35% of the total amount of the plurality of barrier layers.

10. The optoelectronic device according to claim 8 or 9, wherein: The thickness of the barrier layers in the subset of barrier layers is greater than the thickness of the doped region within the barrier layers; optionally, the doped region is not adjacent to the quantum well layer adjacent to the barrier layer.

11. The optoelectronic device according to claims 8 to 10, wherein The dopant concentration in the subset of the plurality of barrier layers is greater than 50% and specifically greater than 55% of the total dopant concentration in the plurality of barrier layers.

12. The optoelectronic device according to any one of claims 8 to 11, wherein The dopant concentration in the barrier layers of the subset of the plurality of barrier layers varies along the thickness of the barrier layers, and in particular increases towards a quantum well layer adjacent to the barrier layers.

13. The optoelectronic device according to any one of claims 8 to 12, wherein The dopant concentration within the subset of the plurality of barrier layers is between 2e17 1 / cm 3 to 5e18 1 / cm 3 and / or The average dopant concentration in the plurality of barrier layers is 1e17 1 / cm 3 to 1e18 1 / cm 3 and / or Wherein the dopant concentration within the subset of the plurality of barrier layers is at least twice an average dopant concentration across the active region.

14. The optoelectronic device of any one of claims 8 to 13, further comprising a dopant within the active region, the dopant being different from silicon.

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