Optoelectronic component and method for producing an optoelectronic component

Abstract

An optoelectronic component according to the invention comprises an epitaxial layer sequence (6) on the basis of a nitride compound semiconductor, said sequence having an active layer (4), wherein the epitaxial growth substrate (1) comprises A11-xGaxN, where 0 < x < 0.95. In a method for producing an optoelectronic component according to the invention, an epitaxial growth substrate (1) made of A11-x(InyGa1-y)xN or In1-xGaxN, where 0 < x < 0.99 and 0 ≤ y ≤1, is provided, and an epitaxial layer sequence (6) on the basis of a nitride compound semiconductor and comprising an active layer (4) is grown thereon by epitaxy.

Description

[0001] Description

[0002] Optoelectronic component and method for manufacturing an optoelectronic component

[0003] The invention relates to an optoelectronic component according to the preamble of claim 1 and a method for its manufacture.

[0004] This patent application claims priority over German patent applications 10 2008 011 864.8 and 10 2008 019 268.6, the disclosure content of which is hereby incorporated by reference.

[0005] In optoelectronic semiconductor devices, such as semiconductor lasers or LEDs, the device lifetime correlates, among other things, with the number of defects in the epitaxially grown semiconductor layers. A high number of defects also reduces the internal quantum efficiency, thereby decreasing the light output. A high-quality growth substrate is required for the epitaxial growth of semiconductor layers with low defect density.

[0006] For the fabrication of optoelectronic components based on nitride compound semiconductors, it is difficult to provide suitable growth substrates that have a lattice constant suitable for growing nitride compound semiconductors and at the same time are characterized by a low defect density on their surface.

[0007] It is known to create epitaxial semiconductor layers from nitride compound semiconductors on SiC or sapphire substrates. to grow up. Growing up in such environments

[0008] However, a comparatively large number of defects arise at the interface between the growth substrate and the epitaxial semiconductor layers. These defects extend from the growth substrate through the device and are therefore also referred to as "threading dislocations." The defects typically exhibit a threading dislocation density (TDD) of more than 10⁻⁶. 8 cm "2 on.

[0009] Meanwhile, GaN substrates are available for the epitaxial growth of nitride compound semiconductors, which have a comparatively low defect density of typically more than 10 5 cm "2 exhibiting these properties. However, the high price of such GaN substrates makes their commercial use in the mass production of optoelectronic components based on nitride compound semiconductors difficult.

[0010] Another disadvantage of using GaN substrates is that the epitaxial layers of the optoelectronic device cannot be easily detached from the growth substrate to produce so-called thin-film devices. Such thin-film devices can be fabricated after the epitaxial layer sequence has been grown on a sapphire substrate, for example, using a laser lift-off process. In the laser lift-off process, laser radiation is shone through the transparent growth substrate and absorbed at the interface between the growth substrate and the epitaxial layer sequence. This absorption of the laser radiation causes material degradation at the interface, leading to the detachment of the growth substrate. Such a The laser lift-off method is known, for example, from publication WO 98 / 14986. However, unlike with sapphire substrates, this method cannot usually be readily applied to GaN substrates because the GaN growth substrate is not transparent.

[0011] The invention is based on the objective of providing an optoelectronic component characterized by a low defect density and comparatively low manufacturing costs. Furthermore, the invention aims to provide a method for manufacturing an optoelectronic component that achieves a low defect density at low manufacturing costs. In particular, it should be possible to detach the growth substrate from the epitaxial layer sequence using a laser lift-off process.

[0012] This problem is solved by an optoelectronic component having the features of claim 1 and a method for its fabrication according to claim 10. Advantageous embodiments and further developments of the invention are the subject of the dependent claims.

[0013] An optoelectronic device according to the invention, comprising an epitaxial layer sequence based on a nitride compound semiconductor with an active layer, has a growth substrate made of Al1- X (In7Ga1^) X N or Ini_ x Ga x N with 0 < x < 0.99 and 0 ≤ y ≤ 1. x < 0.95 is preferred.

[0014] The epitaxial layer sequence is grown epitaxially on the growth substrate, such that its lattice constant is preferentially determined in a direction parallel to the layer plane (in-plane lattice constant) essentially by the in- The plane lattice constant of the growth substrate is determined.

[0015] Such a growth substrate made of Ali- x (In y Gai-y) x N or Irii- x Ga x N with 0 < x < 0.99 and 0 ≤ y ≤ 1 can be produced relatively easily as a bulk material by crystal wax processes and is therefore comparatively inexpensive. This is primarily due to the fact that the bonding forces of the atoms on the surface of these ternary and quaternary nitride compound semiconductors are stronger than the bonding forces on the surface of pure GaN. The comparatively stable crystal surface promotes crystal growth, especially the production of single crystals. Furthermore, such a growth substrate is advantageously characterized by the intrinsic properties of the bulk material. The threading dislocation density (TDD) of the growth substrate is advantageously less than 10 7 cm "2 , especially preferred less than 10 6 cm "2 .

[0016] The low defect density of the growth substrate has a positive effect on the crystal quality of the epitaxial layer sequence. This advantageously increases the lifetime of the optoelectronic component, especially in high-power devices such as semiconductor lasers, and the quantum efficiency of radiation generation.

[0017] The growth substrate can be a free-standing substrate. Alternatively, the growth substrate can also be a so-called quasi-substrate. In the context of this application, a "quasi-substrate" is understood to be a thin layer that has previously been detached from a semiconductor substrate made of the respective semiconductor material and transferred to another support. Such a method for transferring a thin layer of a semiconductor substrate onto another support is known per se from US patent 5,374,564. In this process, ions are implanted through a surface of the semiconductor substrate, thereby creating an ion implantation zone within the substrate. The substrate is then attached to this surface, for example, by means of an intermediate layer such as a solder layer. Subsequently, the semiconductor substrate is annealed along the ion implantation zone, leaving a thin layer of the original semiconductor substrate on the support. This layer can then be used as a growth substrate, for example, for the epitaxial growth of an epitaxial layer sequence of an optoelectronic device.

[0018] The thin layer on the support, acting as a growth substrate, is characterized in particular by the fact that its in-plane lattice constant is essentially determined by the composition of the semiconductor material and is therefore not, or only minimally, influenced by the support. This distinguishes it from a thin epitaxially grown layer, whose in-plane lattice constant is essentially determined by the growth substrate. In contrast to a layer deposited onto the support, the lattice constant of an epitaxially grown layer would only adapt to a lattice constant corresponding to the material composition at large layer thicknesses due to the formation of defects. The epitaxial layer sequence of the optoelectronic device is based on a nitride compound semiconductor. "Based on a nitride compound semiconductor" in this context means that the epitaxial layer sequence, or at least the active layer, is a nitride IIl / V compound semiconductor material, preferably A^Ga^nx- n ^N comprises, where O ≤ n ≤ l, 0 < m < 1 and n+m ≤ 1. This material does not necessarily have to have a mathematically exact composition according to the formula above. Rather, it can contain one or more dopants as well as additional components that exhibit the characteristic physical properties of Al. n Ga m lnx- n - m The N-materials do not change substantially. For the sake of simplicity, however, the formula above only includes the essential components of the crystal lattice (Al, Ga, In, N), even though these may be partially replaced by small amounts of other substances.

[0019] The active layer can be, in particular, a radiation-emitting active layer. The active layer can be configured, for example, as a pn junction, a double heterostructure, a single quantum well structure, or a multiple quantum well structure. The term quantum well structure encompasses any structure in which charge carriers undergo quantization of their energy states through confinement. Specifically, the term quantum well structure does not specify the dimensionality of the quantization. It therefore includes, among other things, quantum wells, quantum wires, and quantum dots, and any combination of these structures.

[0020] In an advantageous embodiment, at least one buffer layer is arranged on the growth substrate. The buffer layer arranged between the growth substrate and the epitaxial layer sequence of the optoelectronic device advantageously achieves a step-like or gradient-like transition of the lattice constant from the growth substrate to the epitaxial layer sequence, thereby advantageously reducing mechanical stresses. Preferably, several buffer layers are applied to the growth substrate so that the lattice constant varies stepwise or in the form of a gradient within the buffer layer sequence.

[0021] Multiple buffer layers made of In are particularly preferred. y Al x Gai- x-yN with x < 0.9 and y < 0.1 are arranged between the growth substrate and the epitaxial layer sequence. The difference in lattice constants between the adjacent buffer layers is preferably kept so small that no additional defects arise due to mechanical stress. The epitaxial layer sequence of the optoelectronic device can thus be advantageously grown onto the uppermost of the buffer layers, which is advantageously characterized by good lattice matching to the epitaxial layers and a low defect density.

[0022] In one embodiment, the epitaxial layer sequence comprises a DBR (Distributed Bragg Reflection) mirror, wherein the DBR mirror has several layer pairs, each comprising a first layer of In y iAl x iGa α _ xl - y iN and a second layer of IR y2 AI x2 Ga1. x2 - y2N is included, where the aluminium content is xl > 0.01 and x2 > 0.05.

[0023] A growth substrate made from Ali. x (In y Gai- y ) x N with 0 < x < 0.99 and 0 ≤ y < 1 has the advantage that the layer pairs of the DBR- Compared to a pure GaN growth substrate, mirrors with the same grating mismatch can exhibit a higher aluminum concentration. By varying the aluminum content (xl ≠ x2) of the alternating layers of the DBR mirror, particularly with xl > 0.01 and x2 > 0.05, the refractive index contrast in the DBR mirror is increased, thus advantageously improving the reflectivity. This has the particular benefit that, compared to a DBR mirror with a lower aluminum content in the layers, the same or even higher reflectivity can be achieved with fewer layer pairs. A smaller number of layer pairs in the DBR mirror offers the advantage of reduced manufacturing effort and improved heat dissipation from the epitaxial layer system due to the reduced overall thickness.

[0024] The DBR mirror is advantageously positioned between the growth substrate and the active layer. This is beneficial for an optoelectronic device where the radiation emitted by the active layer is reflected through the surface opposite the growth substrate. In this case, the DBR mirror reflects the radiation emitted towards the growth substrate to the surface opposite the growth substrate.

[0025] Radiation emission surface. Furthermore, the DBR mirror can form a resonator mirror for a surface-emitting semiconductor laser.

[0026] The optoelectronic component can be a surface-emitting optoelectronic component, in particular a vertical cavity surface-emitting semiconductor laser (VCSEL), a surface-emitting Semiconductor laser with external vertical resonator (VECSEL, Vertical External Cavity Surface Emitting Laser) or an LED, in particular an LED with resonator cavity (RCLED, Resonant Cavity LED) .

[0027] Furthermore, the optoelectronic component can be an edge-emitting semiconductor laser. In an edge-emitting semiconductor laser, the active layer is preferably arranged between two waveguide layers, which form a waveguide in which the radiation emitted by the active layer can propagate in the main emission direction. In a conventional edge-emitting semiconductor laser, cladding layers with a lower refractive index than the waveguide layers border the active layer on both sides, so that the change in refractive index optically guides the wave in the waveguide.

[0028] Since the growth substrate and / or buffer layers in the optoelectronic component have a comparatively low refractive index due to their aluminum content, the cladding layer facing the growth substrate (as viewed from the active layer) can be advantageously omitted. Preferably, therefore, a cladding layer follows only the waveguide layer opposite the growth substrate (as viewed from the active layer), and no cladding layer is arranged between the growth substrate and the waveguide layer facing the growth substrate. This advantageously reduces manufacturing effort and improves heat dissipation towards the growth substrate due to the small overall thickness of the epitaxial layer sequence. To dissipate the heat generated during the operation of the optoelectronic component, the growth substrate is preferably mounted on a heat sink on the side facing away from the active layer. The heat sink can be a passive heat sink, such as a copper block, or an active heat sink, such as a microchannel cooler. It is advantageous that the growth substrate consists of or Ini- x Ga x N, with 0 < x < 0.99 and 0 ≤ y ≤ 1, exhibits improved thermal conductivity compared to conventionally used sapphire or GaN substrates. This allows the heat generated in the active layer to be effectively dissipated to the heat sink via the growth substrate.

[0029] In a method for manufacturing an optoelectronic component according to the invention, a growth substrate made of Ali- x (In y Gai- y ) x N or In1-x Ga x N with 0 < x < 0.99 and 0 ≤ y ≤ 1 provided, and subsequently a nitride compound semiconductor based

[0030] Epitaxial layer sequence, which has an active layer, grown on the growth substrate.

[0031] Preferably, before the

[0032] The epitaxial layer sequence includes at least one buffer layer grown onto the growth substrate. Advantageously, several buffer layers are used. y Al x Gai_ x _ y N with x < 0.9 and y < 0.1 applied to the growth substrate.

[0033] In a further advantageous embodiment, the growth substrate undergoes a temperature treatment before the epitaxial layer sequence or, optionally, one or more buffer layers are grown. By means of the Heat treatment can advantageously remove oxides and carbon compounds from the surface of the growth substrate. Heat treatment is advantageously performed at a temperature above 1000°C. 0 C, preferably at a temperature between 1000 0 The process is carried out at temperatures between 1100°C and 1100°C. The temperature treatment is preferably performed in situ, that is, in the high-vacuum chamber provided for growing the epitaxial layer sequence. Preferably, the temperature treatment is carried out with the supply of H₂ gas or NH₃ gas.

[0034] In a preferred embodiment of the method according to the invention, the growth substrate is removed after the epitaxial layer sequence has been grown.

[0035] The detachment of the growth substrate from the epitaxial layer sequence is advantageously achieved using a laser lift-off method. The laser lift-off method is particularly suitable when the growth substrate is transparent to radiation absorbed by the epitaxial layer sequence, allowing the laser radiation to penetrate the substrate and penetrate the epitaxial layers. This method is therefore especially applicable to an aluminum growth substrate. 1-X (In y Gai- y ) x N with x < 0.99 can be used in contrast to GaN substrates, since the growth substrate has a larger electronic bandgap than GaN due to its aluminum content. The aluminum content of the growth substrate is advantageously chosen such that the growth substrate is transparent to radiation absorbed by the epitaxial layer sequence. An alternative method for separating the growth substrate from the epitaxial layer sequence is to apply a sacrificial layer to the growth substrate before growing the epitaxial layer sequence, with the growth substrate subsequently being removed by selective etching of the sacrificial layer.

[0036] Preferably, the epitaxial layer sequence is bonded to a support at the surface opposite the growth substrate before the growth substrate is detached. Detaching the growth substrate from the epitaxial layer sequence and bonding the epitaxial layer sequence to another support has the advantage that the support does not need to be suitable for the epitaxial growth of a nitride compound semiconductor. Therefore, there is a wide selection of suitable materials for the support. In particular, the support can be made of a material that exhibits good electrical and / or thermal conductivity and / or low cost. For example, the support can be made of Ge, GaAs, Si, SiC, a metal such as Mo or Au, a metal alloy, or a ceramic such as AlN.

[0037] It is advantageous if, before bonding the epitaxial layer sequence to the substrate, a reflection-enhancing layer or layer sequence is applied to the surface of the epitaxial layer sequence facing away from the growth substrate. This is advantageous if the optoelectronic device is an LED, in which radiation emission occurs through the surface opposite the substrate, from which the growth substrate has been detached. The substrate with the reflection-enhancing layer reflects radiation that is in The radiation is radiated in the direction of the carrier, advantageously towards the radiation exit side, so that absorption in the carrier is reduced.

[0038] The epitaxial layer sequence is preferably grown onto the substrate such that first an area of ​​n-doped semiconductor layers is grown, followed by an area of ​​p-doped semiconductor layers, with the active layer positioned between the n-doped and p-doped semiconductor layer regions. Thus, when the substrate is removed after the epitaxial layer sequence has been grown, the n-doped semiconductor layer region is accessible for structuring, unlike in conventional optoelectronic devices.

[0039] Preferably, a structuring process is carried out in the region of the n-doped semiconductor layers after the deposition of the growth substrate. For example, the optoelectronic device can be an LED in which radiation is emitted through the surface where the growth substrate was originally located. Advantageously, a structure is created on this surface, now free of the growth substrate, which improves the extraction of radiation from the semiconductor material. This structure can, in particular, be a roughening or a prism structure.

[0040] The accessibility of the region of the n-doped semiconductor layers of the epitaxial layer sequence for structuring is particularly advantageous when the optoelectronic device is a semiconductor laser. For example, the region of n-doped semiconductor layers are structured to form a finned waveguide, wherein the finned waveguide laser is preferably mounted over the entire surface of a substrate on the side of the p-doped semiconductor layers.

[0041] Structuring n-doped semiconductor layers offers an advantage over conventional optoelectronic devices, where typically the p-doped semiconductor layer is structured, in that a larger number of suitable plasma processes are available for performing the structuring. It has been found that when structuring p-doped semiconductor layers, some plasma processes pose a risk of degrading the electrical properties of the layers during the process. In contrast, the n-doped semiconductor layer is less sensitive, thus reducing the risk of degradation of its electrical properties.

[0042] Detaching the growth substrate from the epitaxial layer sequence is also advantageous when the optoelectronic device is an edge-emitting semiconductor laser. In this case, after detaching the growth substrate, side facets in the epitaxial layer sequence, which form the resonator mirrors of the edge-emitting semiconductor laser, can be generated relatively easily by scribing and splitting the epitaxial layer sequence. The manufacturing effort for generating the reflective side facets is therefore advantageously low. The invention is described below with reference to

[0043] Examples of embodiments are explained in more detail in connection with Figures 1 to 12.

[0044] They show:

[0045] Figure 1 shows a schematic representation of a cross-section through an optoelectronic component according to a first embodiment according to the invention.

[0046] Figure 2 shows a schematic representation of a cross-section through an optoelectronic component according to a second embodiment of the invention.

[0047] Figure 3 shows a schematic representation of a cross-section through an optoelectronic component according to a third embodiment of the invention.

[0048] Figure 4 shows a schematic representation of a cross-section through an optoelectronic component according to a fourth embodiment of the invention.

[0049] Figure 5 shows a schematic representation of a cross-section through an optoelectronic component according to a fifth embodiment of the invention.

[0050] Figure 6 shows a schematic representation of a cross-section through an optoelectronic component according to a sixth embodiment of the invention.

[0051] Figure 7 shows a schematic representation of a cross-section through an optoelectronic component according to a seventh embodiment of the invention. Figure 8 shows a schematic representation of a cross-section through an optoelectronic component according to an eighth embodiment of the invention.

[0052] Figure 9 shows a schematic representation of an embodiment of a method according to the invention, including intermediate steps.

[0053] Figure 10 shows an embodiment of an optoelectronic component produced using the method according to the invention.

[0054] Figure 11 shows a further embodiment of an optoelectronic component produced using the method according to the invention, and

[0055] Figure 12 shows a further embodiment of an optoelectronic component produced using the method according to the invention.

[0056] Identical or similarly functioning components are each marked with the same reference symbols. The components shown, as well as their relative sizes, are not to scale.

[0057] The embodiment of an optoelectronic component shown in Figure 1 is an LED 100. The LED 100 has a growth substrate 1 made of Ali_χ (In7Ga). 1-7 ) X N or Ini- x Ga x N with 0 < x < 0.99 and 0 ≤ y ≤ 1 on . Advantageously, several buffer layers 2 are applied to the growth substrate 1, which y Al x Ga α . x - y exhibit N. Preferably, x < 0.9 and y < 0.1.

[0058] An epitaxial layer sequence 6 is applied to the buffer layers 2. The epitaxial layer sequence 6 comprises an n-doped region 3, which contains one or more

[0059] The n-doped region 3 contains semiconductor layers, and a p-doped region 5 containing one or more semiconductor layers. An active layer 4 is arranged between the n-doped region 3 and the p-doped region 5.

[0060] The layers of the epitaxial layer sequence 6, in particular the active layer 4 contained therein, are based on a nitride compound semiconductor.

[0061] The active layer 4 is a radiation-emitting layer 13, wherein the emitted radiation 13 is preferably radiation from the ultraviolet or from the blue or green visible spectral range. The active layer 4 can be not only a single layer, but can also comprise several sublayers, in particular a single or multiple quantum well structure.

[0062] For electrical contacting of the LED 100, a p-contact layer 11 is applied to the epitaxial layer sequence 6. An n-contact layer 12 can, for example, be applied to the back of the growth substrate 1.

[0063] The growth substrate 1 contained in the LED 100 consists of

[0064] Al1-X (In y Gai_ y ) x N or Ini- x Ga x N with 0 < x < 0.99 and 0 < y ≤ 1 is advantageously characterized by a low defect density of preferably less than 1 x 10 7 cm "2 , especially preferred by less than 1 x 10 6 cm "2A good lattice fit to the epitaxial layer sequence 6 can be achieved by the buffer layer sequence inserted between the growth substrate 1 and the epitaxial layer sequence 6. The compositions of the buffer layers 2 preferably vary stepwise or in the form of a gradient, so that the growth of the buffer layer sequence 2 results in minimal mechanical stress and associated defects. Furthermore, the growth substrate 1 has the advantage of being comparatively inexpensive to produce compared to GaN substrates.

[0065] In the production of the LED 100, a heat treatment of the growth substrate is preferably carried out before the epitaxial growth of the buffer layer sequence 2 onto the growth substrate 1. The heat treatment can advantageously be carried out in situ, i.e., in the coating chamber provided for the epitaxial growth of the subsequent layers. The heat treatment is preferably carried out at a temperature of more than 1000 °C. 0 C, particularly preferably at a temperature between 1000 0 C and 1100 0 C. By means of heat treatment, preferably carried out with the supply of H2-GaS or NH3-GaS, impurities such as oxides or carbon compounds can be advantageously removed from the substrate surface.

[0066] The embodiment of an LED 100 shown in Figure 2 differs from the embodiment shown in Figure 1 in that the n-contact layer 12 is not arranged on the back side of the growth substrate 1. is, but rather how the p-contact layer 11 is arranged on the side of the LED 100 opposite the growth substrate 1. To produce the n-contact, the epitaxial layer sequence 6 is preferably etched down into the n-doped region 3 in an edge region of the LED 100 in order to provide the n-doped region 3 with the n-contact layer 12. The active layer 4 and the p-doped region 5 are thereby isolated from the n-contact layer 12 by an electrically insulating passivation layer 14, which is applied in particular to the exposed side face of the epitaxial layer sequence 6. This type of electrical contact is particularly advantageous when the growth substrate 1 is not electrically conductive.An alternative possibility for electrically contacting the LED 100 in the case of an electrically non-conductive growing substrate is that vias are led from the back of the growing substrate 1 through the growing substrate 1 to the at least one n-doped region 3 (not shown).

[0067] The embodiment of an optoelectronic component shown in Figure 3 is an edge-emitting semiconductor laser 101. Like the LEDs of the previous embodiments, the edge-emitting semiconductor laser 101 is mounted on a growth substrate 1 made of Al1- X (In y Gai- y ) x N or Ini- x Ga x N with 0 < x < 0.99 and 0 ≤ y < 1. Between the growth substrate 1 and the epitaxial layer sequence 6 of the edge-emitting semiconductor laser 101 are several buffer layers 2, which preferably consist of several layers of In y Alx Gai_ x - y N with x < 0.9 and y < 0.1, arranged. The electrical contacting of the edge-emitting semiconductor laser is achieved, for example, by means of a Epitaxial layer sequence 6 applied p-contact layer 11 and an n-contact layer 12 arranged on the back of the growth substrate 1.

[0068] The epitaxial layer sequence 6 of the edge-emitting semiconductor laser contains an active layer 4, which is arranged between a first waveguide layer 9 and a second waveguide layer 10. On the sides facing away from the active layer 4, a first cladding layer 7 borders the first waveguide layer 9 and a second cladding layer 8 borders the second waveguide layer 10.

[0069] Preferably, the first cladding layer 7 and the first waveguide layer 9 facing the growth substrate 1 are n-doped, and the first waveguide layer 10 and second cladding layer 8 arranged above the active layer 4 from the perspective of the growth substrate 1 are p-doped. The cladding layers 7, 8 have a lower refractive index than the waveguide layers 9, 10, thus ensuring that the laser radiation 13, which propagates laterally, is guided in the waveguide layers 9, 10.

[0070] The growth substrate 1 has the advantage of a low defect density, which particularly improves the long-term stability of the edge-emitting semiconductor laser 101. Furthermore, the manufacturing costs are comparatively low compared to the use of a GaN growth substrate.

[0071] Figure 4 shows another embodiment of an edge-emitting semiconductor laser 101. This embodiment differs from the embodiment shown in Figure 3 in that the The epitaxial layer sequence 6 does not contain a first cladding layer facing the growth substrate 1. In this embodiment, the first waveguide layer 9 is therefore applied directly to the buffer layer sequence 2, and only the second waveguide layer 10, located above the active layer 4 as viewed from the growth substrate, borders a second cladding layer 8. The first cladding layer can advantageously be omitted if the growth substrate 1 consists of Al1- X (In y Gax. y J x N or In1- Jc Ga x N with 0 < x < 0.99 and 0 ≤ y < 1 and / or the buffer layer sequence 2, which advantageously comprises several layers of In y Ali_ x Ga xN with x < 0.9 and y < 0.1, has a comparatively low refractive index due to its aluminum content, which is already sufficient for the optical guidance of the laser radiation in the waveguide formed by the active layer 4, the first waveguide layer 9 and the second waveguide layer 10. By omitting the cladding layer facing the growth substrate 1, the

[0072] Manufacturing costs are advantageous. Furthermore, the layer thickness of the epitaxial layer sequence 6 is reduced, which also improves the heat dissipation of the heat generated by the active layer 4 to the growth substrate 1.

[0073] The embodiment of an optoelectronic component shown in Figure 5 is a finned waveguide laser 102. The layer sequence of the finned waveguide laser 102 essentially corresponds to the embodiment of an edge-emitting semiconductor laser shown in Figure 3. The finned waveguide laser 102 differs from the edge-emitting semiconductor laser shown in Figure 3 in that a ridge is generated in the upper cladding layer 8 and the p-contact layer 11 to form a finned waveguide. The bridge can be fabricated, for example, by an etching process in which parts of the p-contact layer 11 and the cladding layer 8 are removed, leaving only a strip-shaped area. The exposed areas of the cladding layer 8 and the p-contact layer 11 are each provided with passivation layers 14. A contact metallization 15 can be applied to the p-contact layer 11, with the areas of the cladding layer 8 located outside the central bridge being insulated from the contact metallization 15 by the passivation layers 14. This type of structuring and contacting restricts the laser emission in the active layer 4 to a central strip-shaped area.

[0074] The n-side contacting of the finned waveguide laser 102 is achieved, for example, by an n-contact layer 12, which can be arranged on the back side of the growth substrate 1 facing away from the active layer 4. In the case of a non-conductive growth substrate 1, the contact layer 12 can also be a through-hole via extending through the growth substrate to the n-doped layers, for example, the buffer layers 2.

[0075] Figure 6 shows another embodiment of a finned waveguide laser 102, which differs from the embodiment shown in Figure 5 in the method of fabricating the n-contact. In the finned waveguide laser 102 shown in Figure 6, the contacting is carried out similarly to the LED shown in Figure 2. The epitaxial layer sequence 6 is etched down in an edge region of the finned waveguide laser 102 to the region of the n-doped semiconductor layers 7, 9, so that these are contacted with an n-contact layer 12. The active layer 4 and the p-doped semiconductor layers 10, 8 are electrically isolated from the n-contact layer 12 by means of a passivation layer 14. This type of electrical contacting is particularly advantageous when the growth substrate 1 is electrically non-conductive.

[0076] The embodiment of an optoelectronic component shown in Figure 7 is a resonant cavity LED (RCLED) 103. Like the previously described embodiments, the RCLED 103 has a growth substrate made of Ali_ x (In y Gai- y ) x N or In1- X Ga x N with 0 < x < 0.99 and 0 ≤ y ≤ 1. Several buffer layers 2 made of In7Al are placed on the growth substrate 1. x Ga1- x _ y N with x < 0.9 and y < 0.1 is applied. An epitaxial layer sequence 6, containing a DBR mirror 16, is applied to the buffer layers 2. The DBR mirror 16 contains a plurality of layer pairs of first and second layers that differ in their material composition and thus in their refractive index.

[0077] Preferably, the layer pairs contain first layers made of In y iAl xiGai.χi-yi and second layers from In y2 Al x2 Gai- x2 - y2 , where the aluminum content advantageously xl > 0.01 and x2 > 0.05 with xl ≠ x2. Because the layer pairs of the DBR mirror 16 can be grown with a comparatively high aluminum content on the growth substrate 1 and the buffer layer sequence 2 applied thereto, it is possible to achieve a higher refractive index contrast between the first and second layers of the DBR mirror 16, so that the number of layer pairs can be reduced compared to a conventional DBR mirror with the same reflectivity. In this way, The thickness of the epitaxial layer sequence 6 is advantageous, which has a positive effect on the heat dissipation of the heat generated by the active layer 4.

[0078] A further advantage for the heat dissipation of the heat generated by the active layer 4 is that the growth substrate consists of Ali_ x (In y Gai- y ) X N or In1- X Ga x N with 0 < x < 0.99 and 0 ≤ y ≤ 1 exhibits a comparatively good thermal conductivity compared to substrates conventionally used for growing nitride compound semiconductors such as sapphire or GaN.

[0079] The semiconductor layers of the DBR mirror 16 are preferably n-doped. The DBR mirror 16 is followed by at least one region of n-doped semiconductor layers 3, the active layer 4, and at least one region of p-doped semiconductor layers 5. A p-contact layer 11 is applied to the p-doped region 5, which reflects back a portion of the radiation 13 emitted by the active layer 4, thus forming a cavity with the DBR mirror 16. In this way, the RCLED 103 emits radiation 13 with high intensity in a preferred direction perpendicular to the active layer 4. To achieve a small beam cross-section, the partially reflective p-contact layer 12 is applied only to a central subregion of the p-doped region 5, with the laterally adjacent regions preferably being provided with a passivation layer 14.

[0080] The advantages of the growth substrate 1 and the DBR mirror 16 applied thereto, described with reference to the embodiment shown in Figure 7, also apply to the optoelectronic component shown in Figure 8, which is This is a surface-emitting semiconductor laser with a vertical resonator (VCSEL) 104. In the surface-emitting semiconductor laser 104, the DBR mirror 16 forms the first resonator mirror for the laser radiation 13. The second resonator mirror 'The surface-emitting semiconductor laser is formed by a second DBR mirror 18, located opposite the first DBR mirror 16 as viewed from the active layer 4. In contrast to the first DBR mirror 16, which is preferably formed from alternating n-doped semiconductor layers, the second DBR mirror 18 is formed from alternating dielectric layers. The second DBR mirror 18 is applied to a transparent contact layer 17, which serves for the electrical contacting of the surface-emitting semiconductor laser 104. The transparent contact layer 17 borders the p-doped region 5 in a central area of ​​the surface-emitting semiconductor laser 104.To restrict the current flow and thus also the generation of laser radiation 13 to a central region of the surface-emitting semiconductor laser 104, the transparent contact layer 17 is isolated from the epitaxial layer sequence in the peripheral regions of the surface-emitting semiconductor laser by passivation layers 14. Laterally to the DBR mirror 18, the transparent contact layer can be provided with contact metallizations 15. The radiation 13 generated by the surface-emitting semiconductor laser 104 is coupled out by the second DBR mirror 18. The electrical contact of the surface-emitting semiconductor laser 104 is achieved firstly by the transparent contact layer 17 in conjunction with the contact metallizations 15 and secondly, for example, by an n-contact layer 12 applied to the back side of the growth substrate. Alternatively, the electrical contact .The activation of the n-doped side of the surface-emitting semiconductor laser 104 can also be carried out as in the finned waveguide laser shown in Figure 6. Alternatively, in the case of a non-conductive growth substrate 1, the n-contact layer 12 can also be electrically connected to the n-doped semiconductor layers of the surface-emitting semiconductor laser 104 by means of vias through the growth substrate 1.

[0081] Figures 9a to 9e illustrate an embodiment of the method according to the invention by means of intermediate steps.

[0082] In the intermediate step shown in Figure 9a, a growth substrate made of Al1- X (In7Ga I - Y ) x N or Ini_ x Ga xN with 0 < x < 0.99 and 0 ≤ y ≤ 1 is provided, onto which the epitaxial layer sequence of an optoelectronic device is to be grown. The growth substrate 1 is advantageously subjected in situ, i.e., in the coating chamber provided for growing the epitaxial layer sequence, to a temperature treatment at a temperature T of preferably more than 1000 0 C, for example between 1000 0 C and 1100 0 C, subjected to. The temperature treatment preferably takes place with the supply of H2 or NH3-GaS and serves to remove carbon and / or oxygen-containing impurities from the surface of the growth substrate 1.

[0083] In the intermediate step shown in Figure 9b, a sequence of semiconductor layers was grown onto the pretreated growth substrate 1. A buffer layer sequence 2, consisting of several layers of In7Al, was then deposited directly onto the growth substrate 1. 3^x Ga xN with x < 0.9 and y < 0.1 The epitaxial layer sequence 6 of the optoelectronic device has been grown onto the buffer layers 2. This sequence contains at least one n-doped semiconductor layer 3, the active layer 4, and at least one p-doped semiconductor layer 5. A p-contact layer 11 is deposited onto the at least one p-doped semiconductor layer 5. The epitaxial layer sequence 6 thus corresponds to the embodiment of an LED shown in Figure 1.

[0084] In the intermediate step of the process shown in Figure 9c, a carrier 19 has been applied to the p-contact layer 11. The carrier 19 is preferably electrically conductive, so that an electrical contact for the optoelectronic component produced by the process can advantageously be realized via the carrier 19.

[0085] Subsequently, the growth substrate 1 is removed using a laser lift-off process. Laser radiation 20 is directed through the growth substrate 1 into the previously deposited semiconductor layers. This process takes advantage of the fact that the growth substrate 1 consists of Al1- X (In7Ga I - Y ) x N or Ini- x Ga xN with 0 < x < 0.99 and 0 ≤ y ≤ 1 is advantageously transparent to laser radiation, which is absorbed by the semiconductor layers. The laser radiation 20 is preferably absorbed in the region of the buffer layer sequence 2, the absorption of the laser radiation 20 causing the semiconductor material to decompose in such a way that the semiconductor body is cut through in this region, as schematically illustrated in Figure 9d. After cutting through the semiconductor body by means of the laser lift-off process, the growth substrate 1, optionally with remnants of the buffer layer sequence 2a, and the epitaxial layer sequence 6 are thus separated from each other on the support 19. The remaining buffer layer sequences 2a and 2b on the separated halves of the semiconductor body can be removed from the growth substrate 1 or the epitaxial layer sequence 6, for example, by means of an etching process. This has the particular advantage that the growth substrate 1 can be reused for growing further semiconductor layer sequences.

[0086] The optoelectronic device is completed in the following process steps using the portion of the separated semiconductor body containing the support 19 and the epitaxial layer sequence 6. Preferably, as shown in Figure 9e, the n-doped region 3 of the epitaxial layer sequence 6, freed from the remnants of the buffer layer sequence, is provided with a structure 21 that improves the radiation extraction from the optoelectronic device. For example, the surface of the n-doped region 3 opposite the support 19, through which the radiation is extracted from the optoelectronic device, can be roughened in such a way that the proportion of the radiation emitted by the active layer 4 that is totally reflected at the interface between the n-doped region 3 and the surrounding medium is reduced.

[0087] Furthermore, at least a partial area of ​​the surface of the n-doped region 3 is provided with an n-contact layer 12 to complete the optoelectronic component, which is an LED 100.

[0088] Figures 10, 11 and 12 show three further embodiments of optoelectronic components. The illustrated examples are manufactured using the method according to the invention. These embodiments have in common that the epitaxial layer sequence contained in these optoelectronic components is each grown on a substrate made of Al1- X (In y Gai- y ) x N or Ini- x Ga xN with 0 < x < 0.99 and 0 ≤ y ≤ 1 was grown, which, after connecting the epitaxial layer sequence on the side opposite the growth substrate with a support, was detached from the epitaxial layer sequence. These procedural steps correspond to the procedural steps explained in connection with Figures 9a to 9d and are therefore not explained in further detail below.

[0089] The optoelectronic components shown in Figures 10, 11, and 12 differ from the embodiment shown in Figure 9e in the type of epitaxial layer sequence 6 and in the structuring of the n-doped semiconductor layers exposed by removing the growth substrate. These differences from the LED 100 shown in Figure 9e are explained in more detail below.

[0090] The optoelectronic device shown in Figure 10 is a finned waveguide laser 102. The epitaxial layer sequence 6 of the finned waveguide laser 102 essentially corresponds to the embodiment shown in Figure 5, that is, it contains an n-doped first cladding layer 7, an n-doped first waveguide layer 9, the active layer 4, a second p-doped waveguide layer 10, and a second p-doped cladding layer 8. In contrast to the embodiment shown in Figure 5, the finned waveguide of the finned waveguide laser 102 is not in the p-doped The cladding layer 8 is not produced in the n-doped cladding layer 7, which is accessible to structuring after detachment of the growth substrate. The n-doped cladding layer 7 is, for example, structured into a finned waveguide by an etching process, with the areas laterally adjacent to the finned waveguide each being provided with passivation layers 14. On the areas provided with the passivation layers 14

[0091] An n-contact layer 12 is applied to the ribbed waveguide. The p-side contact of the strip laser 102 is made via a p-contact layer 11, which is applied to the p-doped cladding layer 8. The electrically conductive carrier 19 is arranged on the p-contact layer 11.

[0092] The creation of the finned waveguide in the n-doped cladding layer 7 has the advantage that the risk of degradation of the electrical properties is reduced, since it has been found that n-doped layers are less sensitive to etching processes, especially plasma etching processes, with regard to their electrical properties compared to p-doped layers.

[0093] Figure 11 shows an embodiment of an optoelectronic device in the form of a vertical surface-emitting semiconductor laser 104 (VCSEL), in which the epitaxial layer sequence 6 is grown on a substrate made of Al1-* (In y Gai -y ) X N or Ini_ x Ga x N with 0 < x < 0.99 and 0 ≤ y ≤ 1 was grown up, which was replaced by the epitaxial layer sequence 6, so that the area of ​​the n-doped semiconductor layers is accessible to structuring. The epitaxial layer sequence 6 of the surface-emitting semiconductor laser 104 comprises at least one p-doped region 5, the active layer 4, an n-doped region 3, and an n-doped DBR mirror 16. The n-doped semiconductor layers 3, 16, and the active layer 4 are structured to form a mesa. A DBR mirror 18, preferably formed of dielectric layers, is deposited on the unstructured p-doped region 5 on the side facing away from the active layer 4. The n-doped DBR mirror 16 and the dielectric DBR mirror 18 form the laser resonator of the surface-emitting semiconductor laser 104.

[0094] The DBR mirror 18 is preferably structured to have the same dimensions as the mesa formed by the active layer 4, the n-doped region 3, and the DBR mirror 16. The dielectric DBR mirror 18 is structured, for example, before the growth substrate is removed and the semiconductor body is bonded to the support 19. The electrical contact of the surface-emitting semiconductor laser 104 is made via p-contact layers 11, which are arranged laterally to the DBR mirror 18 and adjacent to the p-doped region 5. An n-contact layer 12 is deposited on the DBR mirror 16. The n-contact layer 12 is preferably a transparent contact layer, in particular made of an electrically conductive transparent oxide such as ITO or ZnO, or it has a preferably circular opening for coupling out the radiation emitted by the surface-emitting semiconductor laser 104.The carrier 19 is arranged on the DBR mirror 18 and the p-contact layers 11 arranged laterally therefrom. The optoelectronic device shown in Figure 12, which was fabricated using a method according to the invention, is a resonant cavity LED (RCLED) 103. Like the VCSEL shown in Figure 11, the RCLED 103 has a mesa structure comprising the active layer 4, an n-doped region 3, and an n-doped DBR mirror 16. The RCLED 103 also has at least one p-doped region 5. In contrast to the VCSEL described in the previous embodiment, the RCLED 103 does not have a further DBR mirror on the p-doped region 5, but only a partially reflective p-contact layer 11. The RCLED 103 is connected to a conductive substrate 19 at the reflective p-contact layer 11. A second electrical contact of the RCLED 103 is realized by applying an n-contact layer 12 to the n-doped DBR mirror 16.

[0095] The invention is not limited by the description based on the exemplary embodiments. Rather, the invention encompasses every new feature as well as every combination of features, which in particular includes every combination of features in the patent claims, even if this feature or combination itself is not explicitly specified in the patent claims or exemplary embodiments.

Claims

Patent claims 1. Optoelectronic component that uses a nitride compound semiconductor epitaxial layer sequence (6) with an active layer (4), characterized by the fact that it is a growth substrate (1) of Al1.* (ϊnyGai-y)xN or Ini-xGaxN with 0 < x < 0.99 and 0 ≤ y ≤ 1.

2. Optoelectronic component according to claim 1, characterized in that the growth substrate (1) has a defect density of less than 107 cm"2.

3. Optoelectronic component according to claim 1 or 2, characterized in that at least one buffer layer (2) is arranged on the growth substrate (1).

4. Optoelectronic component according to claim 3, characterized in that several buffer layers (2) made of In7AlxGa1-X-7N with x < 0.9 and y < 0.1 are applied to the growth substrate (1).

5. Optoelectronic component according to one of the preceding claims, characterized in that the epitaxial layer sequence (6) comprises a DBR mirror (16), wherein the DBR mirror (16) has several layer pairs, each containing a first layer of InyiAlxxGai-xi-yiN and a second layer of Iny2Alx2Gai-x2-y2N, wherein the aluminium content is xl > 0.01 and x2 > 0.

05.

6. Optoelectronic component according to one of claims 1 to 4, characterized in that the optoelectronic component is an edge-emitting Semiconductor laser (101) is.

7. Optoelectronic component according to claim 6, characterized in that the active layer (4) of the edge-emitting semiconductor laser (101) is located between two waveguide layers (9, 10) are arranged, wherein the waveguide layer (10) opposite the growth substrate (1) as seen from the active layer (4) is followed by a cladding layer (8) and no cladding layer is arranged between the growth substrate (1) and the waveguide layer (9) facing the growth substrate (1).

8. Method for producing an optoelectronic Components, encompassing the process steps: - Providing a growth substrate (1) of Al1-X(InYGa1-Y)xN or In1-XGaxN with 0 < x < 0.99 and 0 ≤ Y ≤ 1, and - Growth of an epitaxial layer sequence (6) based on a nitride compound semiconductor, which includes an active layer (4).

9. Method according to claim 8, characterized in that several buffer layers (2) of InyAlxGax-x-yN with x < 0.9 and y < 0.1 are grown onto the growth substrate (1) before the growth of the epitaxial layer sequence (6).

10. Method according to one of claims 8 or 9, characterized in that the growth substrate (1) is removed after the growth of the epitaxial layer sequence (6).

11. Method according to claim 10, characterized in that the epitaxial layer sequence (6) is connected to a support (19) on the surface opposite the growth substrate (1) before the growth substrate (1) is detached.

12. Method according to one of claims 10 or 11, characterized in that, during the growth of the epitaxial layer sequence (6), first an area of ​​n-doped semiconductor layers (3) and subsequently an area of ​​p-doped semiconductor layers (5) is grown, and in the area of ​​the n-doped semiconductor layers (3) a structuring is carried out after the removal of the growth substrate (1).

13. Method according to claim 12, characterized in that the structuring comprises the fabrication of a structure (21) to improve the radiation extraction from the epitaxial layer sequence (6).

14. Method according to claim 12, characterized in that a strip structure for the production of a finned waveguide laser (102) is generated in the area of ​​the n-doped semiconductor layers (3).

15. Method according to one of claims 8 to 14, characterized in that side facets for an edge-emitting semiconductor laser (101) are generated in the epitaxial layer sequence (6) by scribing and splitting the epitaxial layer sequence (6).