Double-side etching light generation structure and photoelectric device
By etching and setting a reflective grid on the semiconductor layer stack of µLEDs from both sides of the structured mesa, the problem of low light coupling efficiency of µLEDs is solved, achieving high-efficiency light coupling and directionality, which is suitable for AR/VR projection applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-26
- Publication Date
- 2026-03-27
AI Technical Summary
Existing µLEDs have low optical coupling efficiency, leading to problems such as optical crosstalk and insufficient optical coupling, especially in small light-emitting components where it is difficult to achieve efficient optical directionality and focusing.
Structured mesa sections are etched from both sides of the semiconductor layer stack of µLEDs to form inclined sidewall portions, and combined with reflective meshes and light-transmitting top contact elements to form a parabolic mirror structure to improve light coupling efficiency and directionality.
By combining side-mounted etching and reflective structures, the internal quantum efficiency of µLEDs is improved, non-radiative recombination is reduced, and light coupling efficiency and directionality are enhanced, making them suitable for AR/VR projection applications.
Smart Images
Figure CN121753513A_ABST
Abstract
Description
[0001] This application claims priority to German patent application DE 10 2023 123 372.6, filed on August 30, 2023, the disclosure of which is incorporated herein by reference in its entirety.
[0002] The present invention relates to a light-generating structure, an optoelectronic device including the light-generating structure, and a method for manufacturing the optoelectronic device. Background Technology
[0003] Small light-emitting components, particularly red-emitting µLEDs fabricated from InGaAlP, require specific surface passivation techniques, such as regrowth, to ensure high efficiency. In this case, both regrowth and mesa structuring have historically been performed from the same side of the µLED's semiconductor layer stack before transferring it to a carrier substrate. After reattaching the µLED from its growth substrate to its target substrate, the mesa etched structure is embedded in isolation and metallization layers. Additionally, electrical contacts are established around the mesa etched structure to inject current into the µLED's semiconductor layer stack. However, this requires a large remaining area of semiconductor layers in the stack to adequately diffuse the current. On the other hand, insufficient light coupling in the actual emission direction of the µLED can lead to optical crosstalk from the remaining large area of semiconductor layers to adjacent µLEDs.
[0004] Therefore, the purpose of this application is to provide an enhanced light-emitting component that overcomes at least one of the aforementioned disadvantages. Summary of the Invention
[0005] This and other objectives are addressed by the subject matter of the independent claim. Features and other aspects of the proposed principle are outlined in the dependent claims.
[0006] The concept of this invention is to structure the semiconductor layer stack of the light-generating structure, specifically the µLED, after transferring a pre-structured light-generating structure array onto a target substrate, such that the reflective grid for subsequent applications is located deeper within the entire structure, forming a parabolic mirror-like forward coupling structure together with the bottom contact element of the light-emitting component. This results in an increase in overall coupling efficiency and a smaller solid angle for light focusing. The latter is an important requirement for projection applications such as AR / VR. Furthermore, the steps of structuring the semiconductor layer stack of the light-emitting component from two different side mesas of the semiconductor layer stack, isolating it, and depositing the top contact onto the semiconductor layer stack can improve the internal quantum efficiency (IQE) and reduce non-radiative recombination, as current converges from both sides towards the center of the semiconductor layer stack.
[0007] According to a first aspect, a light generating structure is provided. The light generating structure can be particularly part of an optoelectronic device and can particularly be in the form of a small LED or µLED. The light generating structure can be particularly configured to emit light of a desired wavelength or wavelength range when powered. The light generating structure includes a first layer of at least a first conductivity type, a second layer of a second conductivity type, and a semiconductor layer stack of an active region between the first and second layers. The semiconductor layer stack includes a light-emitting surface, a bottom surface opposite to the light-emitting surface, and a first sidewall portion extending from the bottom surface toward the light-emitting surface. The first sidewall portion includes portions of the first layer, the second layer, and the active region.
[0008] The light-generating structure also includes a regenerated layer covering at least the bottom surface and the first sidewall portion, and a bottom contact element disposed on the regenerated layer opposite to the first layer.
[0009] On the other hand, the light-generating structure includes a second sidewall portion that is different from the first sidewall portion, the second sidewall portion extending from the light-emitting surface toward the bottom surface, wherein the second sidewall portion includes at least a portion of the regenerated layer.
[0010] According to some sources, in addition to the portion of the regenerated layer, the second sidewall portion also includes a portion of the second layer.
[0011] The first and second sidewall portions can each be produced by a mesa etching step, specifically a mesa etching step. The first sidewall portion can be produced specifically by a first mesa etching step of the semiconductor layer stack from a first side of the semiconductor layer stack, while the second sidewall portion can be produced specifically by a second mesa etching step of at least a regrown layer from a second side of the semiconductor layer stack, different from the first side, and optionally a second layer of the semiconductor layer stack. By combining these two mesa etching steps with a corresponding arrangement of contact elements, a particularly advantageous structure can be achieved, by which the IQE of the light-generating structure can be increased, for example, by reducing nonradiative recombination due to current concentration from both sides towards the center of the semiconductor layer stack.
[0012] In this regard, the term "sidewall portion" should be understood as at least a portion of the sidewall of the corresponding structure that has been etched. The corresponding structure of the first sidewall portion, etched to the point that it is a first sidewall portion, may specifically be only a stack of semiconductor layers, while the corresponding structure of the second sidewall portion, etched to the point that it is a second sidewall portion, may specifically be not only a stack of semiconductor layers, but also a combination of a stack of semiconductor layers, a regrown layer, and a bottom contact element. Therefore, even though both are referred to as sidewall portions, the first sidewall portion and the second sidewall portion are not limited to sidewall portions of the same body, but may involve different bodies, and thus may at least partially overlap or be located within each other.
[0013] According to some aspects, adjacent first and second sidewall portions are laterally displaced from each other. Specifically, adjacent first and second sidewall portions are laterally shifted towards each other and are not adjacent. This can be particularly achieved by the first sidewall portion being a sidewall portion of a semiconductor layer stack, while the second sidewall portion is not only a sidewall portion of a semiconductor layer stack but also a sidewall portion of a combination of a semiconductor layer stack and a regrown layer. Furthermore, the lateral shift can be achieved by two different etching steps from two different sides of the semiconductor layer stack, the two different etching steps having etched surfaces and cross-sections of different sizes produced by the etching.
[0014] According to some aspects, the first sidewall portion and / or the second sidewall portion is inclined. Specifically, the first sidewall portion can be produced by a first mesa etching step of the semiconductor layer stack from a first side of the semiconductor layer stack, while the second sidewall portion can be produced by a second mesa etching step of at least a regrown layer from a second side of the semiconductor layer stack different from the first side, and optionally a second layer of the semiconductor layer stack. Due to the mesa etching, the resulting sidewall portion can be inclined relative to the perpendicular of the light-emitting surface or the bottom surface. The mesa etching can, in particular, leave a truncated pyramid or truncated cone in each case, whose outer surface forms the first and second sidewall portions at least in certain locations. Specifically, the mesa etching can leave truncated pyramids or truncated cones of different sizes stacked on top of each other, whose outer surfaces form inclined first and second sidewall portions that are laterally separated from each other at least in certain locations.
[0015] Depending on several aspects, the first and second sidewall portions are inclined in different directions. Specifically, adjacent sidewall portions may be inclined in different directions such that they are substantially mirror images or extend in substantially mirror directions. The resulting structure's cross-section may be particularly rhomboid or kite-shaped, with its upper and lower ends being particularly flat. In other words, the resulting structure may be specifically shaped in cross-section as two trapezoids arranged on top of each other, with their longer bases adjacent to each other, and the waists of the trapezoids forming the first and second sidewall portions respectively in at least some places. This may specifically cause the first sidewall portion to be inclined at an angle greater than 90° relative to the luminescent surface, while the second sidewall portion is inclined at an angle less than 90° relative to the luminescent surface, or vice versa, depending on how it is observed.
[0016] According to some aspects, the lateral distance between opposing first sidewall portions increases from the bottom surface toward the light-emitting surface, and the lateral distance between opposing second sidewall portions increases from the light-emitting surface toward the bottom surface. In other words, the structure may include a cross-section in which the lateral distance between opposing first sidewall portions increases from the bottom surface toward the light-emitting surface, and the lateral distance between opposing second sidewall portions increases from the light-emitting surface toward the bottom surface. Such a structure can be generated by stacked trapezoids, triangles, flat or non-flat hemispheres, flat or non-flat semi-ellipses, or other shapes that gradually taper away from the bottom surface.
[0017] Depending on several factors, the luminescent surface is larger than the base surface. This can also be achieved through different etching steps and different structures being etched, resulting in luminescent and base surfaces of varying sizes.
[0018] According to some aspects, semiconductor layer stacks include semiconductor materials such as, for example, indium gallium aluminum phosphide (InGaAlP). However, semiconductor layer stacks may also include semiconductor materials such as, for example, indium gallium arsenide (InGaAs), indium gallium nitride (InGaN), and to name just a few examples. A semiconductor layer stack includes at least a first layer of a first conductivity type, a second layer of a second conductivity type, and an active region between the first and second layers. The first layer may, for example, be a p-doped semiconductor layer, and the second layer may, for example, be an n-doped semiconductor layer. Thus, these two layers can form a pn junction, with the active region disposed therebetween. The active region may, for example, include a quantum well or a multiple quantum well structure, or may, for example, include a quantum dot.
[0019] The light-generating structure can be, in particular, a small light-emitting component / element, such as a miniature LED or µLED. µLEDs can be, in particular, very small LEDs with edge lengths as small as 20 µm, 10 µm, 5 µm, or even smaller. Such small LEDs require special processing and fabrication to improve their IQE and light coupling efficiency. One way to improve the IQE of a µLED is to cover the first sidewall portion with a regenerated layer. Possible methods to improve the coupling efficiency and light directionality of the light emitted by the µLED are to incorporate coupling structures and / or reflective structures on / in the µLED.
[0020] Depending on some aspects, the regenerated layer comprises, for example, a highly Al-containing InGaAlP material and at least one doped or undoped layer with optional additives. However, the regenerated layer may also comprise a highly doped GaP or GaAs contact layer.
[0021] In some respects, the bottom contact element is reflective. By means of a reflective bottom contact element, for example, the coupling efficiency and light directionality of the light emitted by the µLED can be improved, because the light generated in the active region is reflected in the desired direction.
[0022] According to another aspect, an optoelectronic device is provided. The optoelectronic device may be, for example, a light-emitting device comprising one or more light-emitting components, such as a small LED or µLED configured to emit light when powered. The optoelectronic device includes a carrier substrate, a contact layer disposed on the carrier substrate, and at least one light-generating structure according to one or more of the foregoing aspects. A bottom contact element of at least one light-generating structure thereby electrically contacts the contact layer, such that a first potential can be supplied to at least one light-generating structure via the contact layer.
[0023] The optoelectronic device also includes a reflective structure surrounding at least one light-generating structure in the circumferential direction, wherein the reflective structure exposes at least the light-emitting surface and extends from a horizontal level below the active region to a horizontal level above the light-emitting surface. Specifically, the reflective structure provides a reflector surrounding at least one light-generating structure in the circumferential direction, exposing at least the light-emitting surface and extending from a horizontal level below the active region to a horizontal level above the light-emitting surface, to reflect light generated within at least one light-generating structure, and particularly within the active region of at least one light-generating structure, to a desired direction. Due to the fact that the reflective structure extends from a horizontal level below the active region to a horizontal level above the light-emitting surface, the amount of generated light reflected by this reflective structure is higher compared to a reflective structure extending from the light-emitting surface away from the active region away from the at least one light-generating structure. Therefore, the coupling efficiency and directionality of the emitted light from the optoelectronic device can be improved.
[0024] The optoelectronic device further includes: an isolation layer encapsulating at least one light-generating structure in the circumferential direction; and a substantially transparent top contact element electrically contacting a second layer of the at least one light-generating structure, and particularly extending onto a reflective structure. The isolation layer may specifically provide encapsulation to protect the at least one light-generating structure from external influences, and simultaneously provide isolation between certain regions of the optoelectronic device to reduce the risk of short circuits within the optoelectronic device. On the other hand, the top contact element electrically contacting the second layer of the at least one light-generating structure may specifically provide contact such that a second potential can be supplied to the at least one light-generating structure via the top contact element, by means of which, together with a first potential, the at least one light-generating structure can be powered. Therefore, the top contact element may be, for example, a transparent conductive oxide (TCO), such as indium tin oxide (ITO), to be both transmissive to light generated in the at least one light-generating structure and conductive to provide the second potential to the at least one light-generating structure. The top contact element may be limited to covering the light-emitting surface, but may also extend at least partially onto the reflective structure to provide a contact path from the light-emitting surface to an external region of the optoelectronic device.
[0025] According to some aspects, the contact layer conforms to the shape of at least one light-generating structure and is reflective. The contact layer may, for example, form a cavity in which at least one light-generating structure is disposed. The contact layer can thus form a reflector for light generated within the at least one light-generating structure, reflecting light emitted toward the contact layer back toward the light-emitting surface. An isolation layer may be disposed between the contact layer and the at least one light-generating structure, through which the contact layer and the bottom contact element are electrically connected, except for contact vias.
[0026] According to some aspects, the reflective structure, together with the contact layer and / or the bottom contact element of at least one light-generating structure, forms a mirror for light generated in at least one light-generating structure, particularly a parabolic or parabolic mirror. By means of the combined mirror, light generated within at least one light-generating structure can be coupled out of the optoelectronic device in an enhanced manner, and it is possible to focus the light to a smaller solid angle.
[0027] According to some aspects, the reflective structure is a metal mesh surrounding at least one light-generating structure in the circumferential direction. The reflective structure may particularly be in the form of a metal mesh comprising elements surrounding at least one light-generating structure in the circumferential direction, and including strips or the remainder of strips connecting the elements surrounding at least one light-generating structure in the circumferential direction. Due to its conductivity, the metal mesh, together with top contact elements and contact layers, can be particularly used to electrically connect at least one light-generating structure to a current source.
[0028] According to some aspects, an isolation layer is disposed between the regeneration layer of at least one light-generating structure and / or the bottom contact element and a portion of the contact layer. This can be specifically created by: the contact layer having a cavity in which at least one light-generating structure is disposed; and the isolation layer being disposed between at least one light-generating structure and the contact layer.
[0029] According to some aspects, an isolation layer is disposed between a second sidewall portion of at least one light-generating structure and a reflective structure. This can be specifically achieved by the isolation layer surrounding at least one light-generating structure in the circumferential direction and preventing direct contact between the reflective structure and the second sidewall portion.
[0030] According to some aspects, an isolation layer is disposed between a portion of the light-emitting surface of at least one light-generating structure and a top contact element. The isolation layer may, for example, extend partially to the light-emitting surface of at least one light-generating structure to confine the electrical contact between the second layer of the at least one light-generating structure and the top contact element to the center of the light-emitting surface. By means of this, current confinement can be achieved to limit the injected current to the center of at least one light-generating structure. In particular, in this case, the isolation layer comprises a light-transmitting material or a light-transmitting material that does not negatively affect light extraction from the light-emitting surface and therefore from the optoelectronic device, respectively.
[0031] Depending on some aspects, the insulating layer is a reflective material or includes a reflective material. By means of this, the encapsulation of at least one light-generating structure, rather than the light-emitting surface, results in the maximum possible light emission through the light-emitting surface. With the aid of the reflective structure, the light emitted from the light-emitting surface can then be formed and guided in a desired manner.
[0032] According to another aspect, a method for manufacturing an optoelectronic device is provided. The optoelectronic device may be, for example, a light-emitting device comprising one or more light-emitting components, such as small LEDs or µLEDs configured to emit light when powered, and may particularly be an optoelectronic device according to one or more of the foregoing aspects.
[0033] The method includes the following steps:
[0034] A semiconductor layer stack consisting of at least a first layer of a first conductivity type, a second layer of a second conductivity type, and an active region between the first and second layers is disposed on a growth substrate.
[0035] The structured semiconductor layer stack includes a bottom surface and a first sidewall portion extending from the bottom surface in a direction away from the bottom surface. The first sidewall portion includes a first layer, a second layer, and a portion of an active region.
[0036] A regenerated layer is regrowth on the bottom surface and the first sidewall portion;
[0037] Bottom contact elements are disposed on the regenerated layer, opposite to the bottom surface;
[0038] Remove the growth substrate;
[0039] Specifically, by means of a low-damage mesa etching process, a structured semiconductor layer stack and / or a regenerated layer are constructed from a side different from the previous steps of the structured semiconductor layer stack, to obtain a light-emitting surface of the semiconductor layer stack and a second sidewall portion extending from the light-emitting surface in a direction away from the light-emitting surface, the second sidewall portion including portions of the second layer and / or the regenerated layer.
[0040] A reflective structure is disposed around a semiconductor layer stacked in the circumferential direction, wherein the reflective structure exposes at least the light-emitting surface and extends horizontally from below the active region to above the light-emitting surface; and
[0041] A substantially translucent top contact element is provided, which electrically contacts the exposed portion of the second layer and extends specifically to the reflective structure.
[0042] According to some aspects, the method further includes at least one of the following steps:
[0043] A first isolation layer is provided on the bottom contact element and / or the regenerated layer;
[0044] A contact layer is provided on the exposed portion of the first isolation layer and the bottom contact element to electrically contact the bottom contact element;
[0045] A carrier substrate is disposed on the contact layer; and
[0046] A second isolation layer is disposed on the light-emitting surface and / or the regenerated layer and / or the first isolation layer.
[0047] According to some aspects, the first isolation layer and the second isolation layer together form a combined / single isolation layer, as described for an optoelectronic device according to one or more of the foregoing aspects.
[0048] According to some aspects, the steps of stacking structured semiconductor layers and / or stacking and / or regrowing layers are mesa etching processes, particularly mesa etching processes from different sides of the semiconductor layer stack.
[0049] According to some aspects, this method is a method for manufacturing an optoelectronic device according to one or more of the foregoing aspects. In particular, all the features, advantages, configurations, and arrangements described with respect to light-generating structures and optoelectronic devices also apply to the method for manufacturing optoelectronic devices, and vice versa. Attached Figure Description
[0050] Further aspects and implementations based on 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:
[0051] Figure 1 Cross-sectional views of an optoelectronic device based on some aspects of the proposed principles are shown; and
[0052] Figures 2A to 12B The steps of two embodiments for manufacturing optoelectronic devices are shown, based on some aspects of the proposed principles. Detailed Implementation
[0053] The following embodiments and examples disclose various aspects and combinations thereof based on the proposed principles. The embodiments and examples are not always drawn to scale. Similarly, different elements may be enlarged or reduced in size to emphasize various aspects. It goes without saying that the various aspects of the embodiments and examples shown in the figures can be combined with each other without difficulty, which does not contradict the principles of the invention. Some aspects illustrate regular structures or forms. It should be noted that in practice, minor differences and deviations from the ideal form may occur; however, this does not contradict the concept of the invention.
[0054] Furthermore, the various figures and aspects are not necessarily shown at the correct dimensions, and the proportions between the elements need not be substantially accurate. Some aspects are highlighted by showing them enlarged. However, terms such as "above," "over," "below," "under," "larger," and "smaller" are correctly used to represent the elements in the figures. Therefore, such relationships between elements can be inferred from the figures.
[0055] Figure 1 A cross-sectional view of an optoelectronic device 10 based on some aspects of the proposed principles is shown. The optoelectronic device 10 includes a carrier substrate 11 and a contact layer 12 disposed on the carrier substrate 11. A light generating structure 1 is disposed within a cavity 17 of the contact layer 12, on the contact layer 12, and electrically coupled to the contact layer 12.
[0056] The light-generating structure 1 itself comprises a first layer 3 of a first conductivity type, a second layer 4 of a second conductivity type, and a semiconductor layer stack 2 of an active region 5 between the first layer 3 and the second layer 4. The semiconductor layer stack 2 is formed such that it includes a light-emitting surface 6a, a bottom surface 6b opposite to the light-emitting surface 6a, and a first sidewall portion 6c extending from the bottom surface 6b toward the light-emitting surface 6a. The first sidewall portion 6c thereby includes portions of the first layer 3, the second layer 4, and the active region 5, particularly the side portion.
[0057] The light-generating structure 1 also includes a regenerated layer 7, which is grown on and covers the bottom surface 6b and the first sidewall portion 6c, and in the illustrated embodiment extends to the surface of the second layer 4 adjacent to the first sidewall portion 6c. Additionally, the light-generating structure 1 includes a bottom contact element 8, which is disposed opposite to the first layer 3 on the regenerated layer 7 and follows the regenerated layer 7 along the first sidewall portion 6c, thereby more or less encapsulating the regenerated layer 7 in the region of the bottom surface 6b and the first sidewall portion 6c.
[0058] In addition to the first sidewall portion 6c of the semiconductor layer stack 2, the light generating structure 1 also includes a second sidewall portion 9 that is different from the first sidewall portion 6c. The second sidewall portion 9 extends from the light-emitting surface 6a toward the bottom surface 6b. In the illustrated embodiment, the second sidewall portion 6c includes a portion of the regenerated layer 7 and the second layer 4, particularly the side portion.
[0059] Therefore, the first sidewall portion 6c is formed by the semiconductor layer stack 2, while the second sidewall portion 9 is formed by the regenerated layer 7 and the second layer 4 of the semiconductor layer stack 2.
[0060] The present invention is conceived in fabricating the light-generating structure 1 such that the first sidewall portion 6c is produced by a different etching step than the second sidewall portion 9, and specifically by two different etching steps on opposite sides of the semiconductor layer stack 2, resulting in the structure shown. The advantage of combining this structure with the components described later is that it provides an optoelectronic device by means of which improved coupling efficiency and focusing of light to a smaller solid angle generated in the light-generating structure can be achieved. Furthermore, the mesa structuring from the two different sides of the semiconductor layer stack 2, combined with the top contact deposition on the semiconductor layer stack 2 described later, can improve the internal quantum efficiency (IQE) / reduce nonradiative recombination due to the current converging from both sides towards the center of the semiconductor layer stack 2.
[0061] Due to two distinct etching steps, particularly the mesa etching step, the first sidewall portion 6c and the second sidewall portion 9 are inclined in different directions. Specifically, adjacent sidewall portions are inclined in different directions, making them essentially mirror images of each other. When viewed in the illustrated cross-section, the resulting structure takes the form of two trapezoids arranged one on top of the other, with their longer bases adjacent to each other, and the waists of the trapezoids forming the first sidewall portion 6c and the second sidewall portion 9 respectively in at least some locations. Therefore, the lateral distance between the opposing first sidewall portions 6c increases from the bottom surface 6b towards the light-emitting surface 6a, and the lateral distance between the opposing second sidewall portions 9 increases from the light-emitting surface 6a towards the bottom surface 6b.
[0062] The optoelectronic device 10 also includes a reflective structure 13 surrounding at least one light-generating structure 1 in the circumferential direction U, wherein the reflective structure 13 exposes the light-emitting surface 6a and extends horizontally from below the active region 5 to above the light-emitting surface 6a. "Below the active region 5" can, for example, mean that the reflective structure 13 extends horizontally between the active region 5 and the bottom surface 6b (including the active region 5 and the bottom surface 6b), while "above the light-emitting surface 6a" can, for example, mean above the light-emitting surface 6a in the direction from the bottom surface 6b to the light-emitting surface 6a. Therefore, the reflective structure 13 protrudes from the light-generating structure 1 in the direction from the bottom surface 6b to the light-emitting surface 6a and in the opposite direction from the active region 5. By means of this, the amount of generated light L reflected by the reflective structure 13 is higher than that of a reflective structure extending "only" from the light-emitting surface 6a in the direction from the bottom surface 6b to the light-emitting surface 6a. Therefore, the coupling efficiency and directionality of the emitted light L of the optoelectronic device 10 can be improved.
[0063] The reflective structure 13 is specifically in the form of a ring surrounding the light generating structure 1, which has a tapered inner surface, to guide / reflect light generated within the light generating structure 1 in a desired direction. The reflective structure 13, together with the bottom contact element 8 (a reflective material in the illustrated embodiment), forms a mirror structure, guiding / reflecting light generated within the light generating structure 1 in a desired direction. The mirror structure and the reflection of light L... Figure 1 The dashed semi-ellipse and the reflected arrow indicating the reflected light L are used for indication.
[0064] The light generating structure 1 and the reflective structure 13 are partially embedded in the insulating layer 14. The insulating layer 14 encapsulates the light generating structure 1 in the circumferential direction U and extends partially to the light-emitting surface 6a and the bottom contact element 8 opposite the bottom surface 6b. On the one hand, the isolation holds all components in place, protects the light generating structure 1 from external influences, and prevents short circuits within the optoelectronic device 10. Since the insulating layer 14 extends partially to the light-emitting surface 6a, it is a light-transmitting material, at least for light generated within the active region 5 of the light generating structure 1.
[0065] For electrical contact, in addition to the contact layer 12, the optoelectronic device 10 also includes a substantially transparent top contact element 15 that electrically contacts the second layer 4 of the light-generating structure 1. The top contact element 15 may, for example, comprise ITO and is configured to provide a potential to the second layer 4 of the light-generating structure 1. In the illustrated embodiment, the top contact element 15 not only covers the light-emitting surface 6a but also extends to the reflective structure 13. This allows the top contact element 15 to make electrical contact outside the light-emitting region, thereby not negatively impacting the coupling efficiency of the optoelectronic device later.
[0066] The illustrated embodiment shows only a single light generating structure 1 included in the optoelectronic device 10. However, an optoelectronic device 10 may also include several light generating structures 1 adjacent to each other, surrounded by a single reflective structure 13 or by separate reflective structures 13. For example, it is conceivable that three light generating structures 1 are surrounded by a single reflective structure 13, wherein the three light generating structures 1 are configured to emit red, green, and blue light, together forming an RGB pixel. For example, it is also conceivable to arrange several similar light generating structures 1, surrounded by a single reflective structure 13, to provide brighter light of a corresponding wavelength, or to provide a "backup" light generating structure in case other light generating structures 1 fail. However, this is only illustrative, and the number of light generating structures 1 and the wavelength of the light emitted by the light generating structures 1 can be chosen differently. Furthermore, the electrical contacts of the several light generating structures 1 can be varied, such that all or some of the light generating structures 1 can operate individually, and / or all or some of the light generating structures 1 can be connected, such that they operate simultaneously.
[0067] Figures 2A to 12B The steps of two embodiments of the method for manufacturing an optoelectronic device, based on some aspects of the proposed principles, are illustrated. Therefore, Figure "X"A shows the steps of a first embodiment of the method for manufacturing an optoelectronic device, based on some aspects of the proposed principles, while Figure "X"B shows the steps of a second embodiment of the method for manufacturing an optoelectronic device, based on some aspects of the proposed principles. Therefore, the variable "X" represents the numbers 2 to 12.
[0068] like Figure 2A and Figure 2B As shown, in the first step, the growth substrate 16 is provided with a semiconductor layer stack 2 epitaxially grown on top. The semiconductor layer stack 2 includes a first layer 3 of a first conductivity type, a second layer 4 of a second conductivity type, and an active region 5 between the first layer 3 and the second layer 4.
[0069] like Figure 3A and Figure 3B As shown, in the second step, a first mesa etching step is performed. The first mesa etching step structures the semiconductor layer stack 2, resulting in the exposed portion of the semiconductor layer stack 2 including the bottom surface 6b and the inclined first sidewall portion 6c. Figure 3B In comparison, such as Figure 3A As shown, etching is performed such that it does not penetrate the entire second layer 4, but stops well before reaching the growth substrate 16. On the other hand, as... Figure 3B As shown, etching is performed so that it penetrates the entire second layer 4 and stops upon reaching the growth substrate 16. Therefore, the exposed portion is trapezoidal in shape as shown in the cross-section. Figure 3A In this case, it can be arranged on the remaining part of the second layer 4, or as follows: Figure 3B As shown, it is arranged on the growth substrate 16.
[0070] like Figure 4A and Figure 4B As shown, in the next step, a regrown layer 7 is regrown on the mesa etched structure and following the shape of the mesa etched structure. The regrown layer 7 is regrown such that it at least covers the bottom surface 6b and the first sidewall portion 6c. The regrown layer 7 can be grown, for example, by means of an MOVPE epitaxial process. In addition to the bottom surface 6b and the first sidewall portion 6c, the regrown layer 7 also... Figure 4A In the case of covering the remaining part of the second layer 4, or as... Figure 4B The growth substrate 16 shown is adjacent to the first sidewall portion 6c. The regrown layer 7 may, for example, include a thickness between 30 nm and 400 nm.
[0071] Figure 5A and Figure 5B The following steps are illustrated for forming a bottom contact layer 8a on the regenerated layer 7, following the shape of the regenerated layer 7. The bottom contact layer 8a is a conductive layer and may be, for example, a metal or a TCO such as ITO. The bottom contact layer 8a may be, for example, sputtered, spin-coated, or sprayed onto the regenerated layer 7, and may include, for example, a metal oxide such as ITO, or a material such as ZnO, Au, AuGe, or Ag. In the illustrated embodiment, the bottom contact layer 8a is formed over the entire regenerated layer 7 and is structured in a subsequent step to form the later bottom contact element 8; however, it is also conceivable to form a bottom contact layer 8a already structured on the regenerated layer 7 to form the later bottom contact element 8.
[0072] like Figure 6A and Figure 6B As shown, in the following steps, following the shape of the existing structure, a first isolation layer 14a is provided on the structured bottom contact layer 8a and the regeneration layer 7, covering the top side of the existing structure. The first isolation layer 14 may include, for example, Al2O3, SiO2, SiNx, or Nb2O5, and may be applied, for example, by means of CVD, PVD, or ALD. In the illustrated embodiment, the first isolation layer 14a is provided on the entire top side of the existing structure (structured bottom contact layer 8a and regeneration layer 7), and is structured in a subsequent step to expose a portion of the bottom contact element 8. However, it is also conceivable to provide a first isolation layer 14a that has already been structured on the existing structure to expose a portion of the bottom contact element 8.
[0073] like Figure 7A and Figure 7BAs shown, a contact layer 12 is then provided on the first isolation layer 14a, contacting the exposed portion of the bottom contact element 8. The contact layer 12 follows the shape of the first isolation layer 14a on its side facing the first isolation layer 14a, and forms a substantially flat surface on its side opposite to the first isolation layer 14a. The carrier substrate 11 is then provided on this substantially flat surface.
[0074] Because the contact layer 12 follows the shape of the first isolation layer 14a on its side facing the first isolation layer 14a, the contact layer 12 forms a cavity 17 in which the mesa etched portion of the semiconductor layer stack 2 is disposed. The contact layer 12 is conductive and, in particular, a reflective material to provide electrical connection to the bottom contact element on one hand, and to form a back mirror of the semiconductor layer stack 2 on the other hand. Therefore, the cavity 17 helps to reflect light generated within the semiconductor layer stack 2 in a guided manner to a desired direction. The contact layer 12 may, for example, comprise a solder material, upon which the carrier layer 11 is bonded. The carrier layer may, for example, be or comprise an integrated circuit.
[0075] like Figure 8A and Figure 8B As shown, in a subsequent step, the growth substrate 16 is removed. For this purpose, the structure can be flipped to remove the growth substrate 16, so that the exposed surface faces upward, allowing the structure to be processed from the exposed surface side. The removal of the growth substrate 16 exposes the surface of the semiconductor layer stack 2, which later forms the light-emitting surface 6a of the light-generating structure within the optoelectronic device.
[0076] Then, as Figure 9A and Figure 9B As shown, after removing the growth substrate 16, there is a second mesa etching step. The second mesa etching step is... Figure 9A In the case of structuring the remaining part of the second layer 4 and the regenerated layer 7, while Figure 9B In this case, only the structured regeneration layer 7 is regenerated, resulting in the inclined second sidewall portion 9. (Compared to...) Figure 9B In comparison, such as Figure 9A As shown, etching is performed such that it penetrates the remainder of the second layer 4 and the regenerated layer 7, stopping upon reaching the first isolation layer 14a. On the other hand, as... Figure 9BAs shown, etching is performed such that the etching penetrates the regenerated layer 7 and stops upon reaching the first isolation layer 14a. Therefore, the exposed portion is arranged in a larger, mirrored trapezoidal form on the existing trapezoid of the semiconductor layer stack 2, as shown in the cross-section. Thus, the second etching step, performed from a direction different from the first etching step, produces a structure that resembles a rhombus or kite with flattened upper and lower apexes in the cross-section shown. Therefore, the resulting structure can be manufactured using only the described technique (i.e., etching from two different sides of the semiconductor layer stack 2), not only due to the sidewall portions tilted in different directions but also due to the lateral offset between the sidewalls.
[0077] Due to the second etching step, a light-generating structure is created within the optoelectronic device, wherein the light-generating structure includes a structured semiconductor layer stack 2, a structured regenerated layer 7, and a bottom contact element 8.
[0078] like Figure 10A and Figure 10B As shown, in the following steps, following the shape of the existing structure, a second isolation layer 14b is disposed on the first isolation layer 14a and the light-generating structure, covering the top side of the existing structure. The second isolation layer 14b may include, for example, Al2O3, SiO2, SiNx, or Nb2O5, and may be applied, for example, by means of CVD, PVD, or ALD. In the illustrated embodiment, the second isolation layer 14b is disposed on the entire top side of the existing structure (the first isolation layer 14a and the light-generating structure), and in subsequent steps, such as Figure 11A and Figure 11B As shown, the structure is arranged to expose a portion of the light-emitting surface 6a. However, it is also conceivable to provide a second insulating layer 14b, already structured on the existing structure, to expose a portion of the light-emitting surface 6a. The first insulating layer 14a and the second insulating layer 14b are, in particular, made of the same material and together form a common insulating layer 14.
[0079] In subsequent steps, such as Figure 12A and Figure 12B As shown, a reflective structure 13 is then provided around the light-generating structure 1 in the circumferential direction, wherein the reflective structure 13 exposes the light-emitting surface 6a and extends horizontally from below the active region 5 to above the light-emitting surface 6a. Therefore, the insulating layer can be structured, for example, to provide a corresponding cavity, in which the reflective structure 13 is arranged. Furthermore, a substantially transparent top contact element 15 is provided, electrically contacting the second layer 4 of the light-generating structure 1, extending throughout the existing structure and extending onto the reflective structure 13. The top contact element 15 can be, for example, a TCO such as ITO, to provide an electrical top contact for the light-generating structure 1. Based on some aspects of the proposed principles, the resulting structure forms an optoelectronic device 10.
[0080] exist Figures 2A to 12B In the illustrated embodiments, only one optoelectronic device 10 is shown for each example. However, it should be understood that the method of manufacturing may include manufacturing the entire wafer, on which the optoelectronic devices 10 are arranged adjacent to each other in the same manner as described. The reflective structure 13 may then be, for example, in the form of a grid disposed on the entire wafer, wherein the grid includes elements surrounding the light generating structure 1 in the circumferential direction, such as... Figure 12A and Figure 12B As shown, there are strips between the components to hold them in place.
[0081] List of reference numerals
[0082] 1. Light generation structure
[0083] 2 semiconductor layer stacks
[0084] 3 First layer
[0085] 4. Second layer
[0086] 5 active areas
[0087] 6a luminescent surface
[0088] 6b bottom surface
[0089] 6c First sidewall portion
[0090] 7 Regeneration Layer
[0091] 8a Bottom Contact Layer
[0092] 8 Bottom contact elements
[0093] 9. Second sidewall portion
[0094] 10 Optoelectronic Devices
[0095] 11 Carrier substrate
[0096] 12 contact layers
[0097] 13 Reflection Structure
[0098] 14, 14a, 14b isolation layers
[0099] 15 Top Contact Components
[0100] 16 Growth substrate
[0101] 17 chambers
[0102] L-light
[0103] U-shaped direction
Claims
1. A light-generating structure (1), comprising: A semiconductor layer stack (2) consisting of at least a first layer (3) of a first conductivity type, a second layer (4) of a second conductivity type, and an active region (5) between the first layer (3) and the second layer (4), the semiconductor layer stack (2) comprising a light-emitting surface (6a), a bottom surface (6b) opposite to the light-emitting surface (6a), and a first sidewall portion (6c) extending from the bottom surface (6b) toward the light-emitting surface (6a), wherein the first sidewall portion (6c) comprises portions of the first layer (3), the second layer (4), and the active region (5); A regrowth layer (7) covering at least the bottom surface (6b) and the first sidewall portion (6c); and Bottom contact element (8) arranged on the regenerated layer (7) and opposite to the first layer (3); The light-generating structure (1) includes a second sidewall portion (9) different from the first sidewall portion (6c). The second sidewall portion (9) extends from the light-emitting surface (6a) toward the bottom surface (6b). The second sidewall portion (6c) includes at least a portion of the regenerated layer (7). The first sidewall portion (6c) and the second sidewall portion (9) are inclined in different directions.
2. The light-generating structure (1) according to claim 1, wherein, The second sidewall portion (9) includes a portion of the second layer (4).
3. The light-generating structure (1) according to claim 1 or 2, wherein, The adjacent first sidewall portion (6c) and second sidewall portion (9) are laterally separated from each other.
4. The light-generating structure (1) according to any one of the preceding claims, wherein, The first sidewall portion (6c) and / or the second sidewall portion (9) are inclined.
5. The light-generating structure (1) according to any one of the preceding claims, wherein, The lateral distance between the opposing first sidewall portions (6c) increases from the bottom surface (6b) toward the light-emitting surface (6a), and the lateral distance between the opposing second sidewall portions (9) increases from the light-emitting surface (6a) toward the bottom surface (6b).
6. The light-generating structure (1) according to any one of the preceding claims, wherein, The light-emitting surface (6a) is larger than the bottom surface (6b).
7. The light-generating structure (1) according to any one of the preceding claims, wherein, The regenerated layer (7) comprises a highly doped semiconductor material.
8. The light-generating structure (1) according to any one of the preceding claims, wherein, The bottom contact element (8) is reflective.
9. An optoelectronic device (10), comprising: Carrier substrate (11); A contact layer (12) disposed on the carrier substrate (11); At least one light generating structure (1) according to any one of the preceding claims is disposed on the contact layer (12), wherein the bottom contact element (8) of at least one light generating structure (1) is in electrical contact with the contact layer (12). A reflective structure (13) surrounding the at least one light-generating structure (1) in the circumferential direction (U), wherein the reflective structure (13) exposes at least the light-emitting surface (6a) and extends from the level below the active region (5) to the level above the light-emitting surface (6a); An isolation layer (14) encapsulates the at least one light-generating structure (1) in the circumferential direction (U); and The top contact element (15) is substantially transparent to light, which is in electrical contact with the second layer (4) of the at least one light generating structure (1) and extends particularly to the reflective structure (13).
10. The optoelectronic device (10) according to claim 9, wherein, The contact layer (12) follows the shape of the at least one light-generating structure (1) and is particularly reflective.
11. The optoelectronic device (10) according to claim 9 or 10, wherein, The reflective structure (13) together with the contact layer (12) and / or the bottom contact element (8) of the at least one light generating structure (1) forms a mirror, particularly a parabolic mirror, for the light (L) generated in the at least one light generating structure (1).
12. The optoelectronic device (10) according to any one of claims 9 to 11, wherein, The reflective structure (13) is a metal mesh surrounding the at least one light-generating structure (1) in the circumferential direction (U).
13. The optoelectronic device (10) according to any one of claims 9 to 12. in, The isolation layer (14) is disposed between the regeneration layer (7) of the at least one light-generating structure (1) and / or the bottom contact element (8) and the contact layer (12); and / or Wherein, the isolation layer (14) is disposed between the second sidewall portion (9) of the at least one light generating structure (1) and the reflective structure (13); and / or The isolation layer (14) is disposed between a portion of the light-emitting surface (6a) of the at least one light-generating structure (1) and the top contact element (15).
14. The optoelectronic device (10) according to any one of claims 9 to 13, wherein, The isolation layer (14) is substantially transparent.
15. A method for manufacturing an optoelectronic device (10), comprising the following steps: A semiconductor layer stack (2) is formed on a growth substrate (16) comprising at least a first layer (3) of a first conductivity type, a second layer (4) of a second conductivity type, and an active region (5) between the first layer (3) and the second layer (4). The semiconductor layer stack (2) is structured such that the structured semiconductor layer stack includes a bottom surface (6b) and a first sidewall portion (6c) extending from the bottom surface (6b) in a direction away from the bottom surface (6b), the first sidewall portion (6c) including portions of the first layer (3), the second layer (4) and the active region (5); A regenerated layer (7) is regenerated on the bottom surface (6b) and the first sidewall portion (6c). A bottom contact element (8) is provided on the regenerated layer (7) opposite to the bottom surface (6b); Remove the growth substrate (16); The semiconductor layer stack (2) and / or the regenerated layer (7) are structured from a side different from the previous steps of structuring the semiconductor layer stack (2) to obtain a light-emitting surface (6a) of the semiconductor layer stack (2) and a second sidewall portion (9) extending from the light-emitting surface (6a) toward the bottom surface (6b), the second sidewall portion (9) including a portion of the second layer (4) and / or the regenerated layer (7); A reflective structure (13) is disposed around the semiconductor layer stack (2) in the circumferential direction (U), wherein the reflective structure (13) exposes at least the light-emitting surface (6a) and extends from the horizontal below the active region (5) to the horizontal above the light-emitting surface (6a); as well as A substantially translucent top contact element (15) is provided, which electrically contacts the exposed portion of the second layer (4) and extends particularly to the reflective structure (13).
16. The method of claim 15, further comprising at least one of the following steps: A first isolation layer (14a) is provided on the bottom contact element (8) and / or the regeneration layer (7); A contact layer (12) is provided on the exposed portion of the first isolation layer (14a) and the bottom contact element (8) to electrically contact the bottom contact element (8). A carrier substrate (11) is disposed on the contact layer (12); and A second isolation layer (14b) is provided on the light-emitting surface (6a) and / or the regenerated layer (7) and / or the first isolation layer (14a).
17. The method according to claim 15 or 16, wherein, The steps of structuring the semiconductor layer stack (2) and / or structuring the semiconductor layer stack (2) and / or the regenerated layer (7) are mesa etching processes, particularly mesa etching processes from different sides of the semiconductor layer stack (2).
18. The method according to any one of claims 15 to 17, wherein, The method is a method for manufacturing an optoelectronic device (10) according to any one of claims 9 to 14.