Surface emitter and methods for producing surface emitters

Abstract

The invention relates to a surface emitter (100) and methods (200, 400, 600) for producing surface emitters (100), wherein one method for producing surface emitters comprises: providing a substrate structure, comprising: a substrate having a plurality of depressions and a plurality of ridges, each ridge of which is arranged between two depressions directly adjacent to one another from the plurality of depressions, and a plurality of epitaxial layers, each epitaxial layer being arranged over a ridge from the plurality of ridges and extending beyond the ridge in a lateral direction in such a way that each of the two depressions directly adjacent to one another forms an associated gap between the epitaxial layer and the substrate; forming a plurality of surface emitter structural elements by forming at least one surface emitter structural element over a top side of each epitaxial layer, said top side facing away from the substrate; and forming a mirror structure at least over the plurality of surface emitter structural elements and over exposed sections of an underside of each epitaxial layer, said underside facing the substrate. Figure 3A

Description

[0001] Surface emitters and methods for producing

[0002] Surface emitters

[0003] Description

[0004] Various embodiments relate to a surface emitter (vertical cavity surface emitting laser, VCSEL) and methods for its manufacture.

[0005] Surface emitters can serve as light sources for a wide variety of applications in numerous fields, such as point emitters for biometric facial recognition in smartphones, security systems, etc. A surface emitter is a laser diode that emits light perpendicular to the plane of the semiconductor chip. Surface emitters provide a cost-effective light source with high beam quality and small dimensions. In a surface emitter, a light-emitting, active region, formed by epitaxial growth, is typically arranged vertically between two Bragg mirrors (distributed Bragg reflectors, DBR).

[0006] The epitaxial mirror layers of the two Bragg mirrors can be produced on various material systems during the manufacture of a surface emitter, such as aluminum gallium arsenide (AlGaAs) or gallium nitride (GaN). In contrast to the AlGaAs material system, however, it is very difficult to grow the highly reflective mirror layers epitaxially on GaN. Therefore, various approaches are conventionally used to enable the epitaxial growth of the mirror layers on GaN. In one example, the mirror layers can have porosified or undercut layers of aluminum indium gallium nitride. In another example, dielectric mirrors are used on the back of the substrate, but this results in comparatively large cavities, which necessitate a concave mirror on the back of the substrate.In yet another example, epitaxial layers are removed from a substrate by (photo) electrochemical etching, which, however, requires relatively complex processing with rebonding.

[0007] These approaches to forming mirror layers on GaN are technically complex and therefore cost-intensive.

[0008] According to various aspects, methods are provided that enable cost-effective and mass-producible production of GaN-based surface emitters. For example, numerous such surface emitters can be formed simultaneously on a substrate (e.g., wafer). These methods are therefore scalable. These methods make it possible to produce a surface emitter in which an epitaxial (e.g., GaN-containing) layer is arranged directly above a mirror structure with non-epitaxial mirror layers. In one aspect, an epitaxial process is used in which, after the epitaxy of the GaN-based layer, both sides of the GaN-based layer are accessible, whereby the mirror layers of both Bragg mirrors can be formed in a single coating process (e.g., as non-epitaxial layers) (e.g., by means of atomic layer deposition (ALD)).In another aspect, one of the two mirrors is formed from non-epitaxial mirror layers prior to the GaN-based layer, and the GaN-based layer is subsequently formed over this mirror using an epitaxial lateral overgrowth (ELOG) process.

[0009] The production of non-epitaxial mirror layers is not only more cost-effective, but the non-epitaxial mirror layers also have greater refractive index contrasts compared to epitaxially grown (Al InGa ) N mirrors . Furthermore, the methods described herein enable precise control of the layer thickness of the epitaxial layer . Using this layer thickness, for example, the cavity length, which is very critical for surface emitters, can be very well adjusted . In the drawings, like reference numerals generally refer to like parts throughout the different views . The drawings are not necessarily to scale, the emphasis generally being placed upon illustrating the principles of the invention . In the following description, various aspects of the invention are described with reference to the following drawings, in which:

[0010] FIG. 1A to FIG. 1E each show a schematic cross-sectional view of a surface emitter according to various aspects;

[0011] FIG. 2 shows a flow diagram of a method for manufacturing surface emitters according to various aspects; FIG. 3A and FIG. 3B show schematic cross-sectional views of the manufacturing process of the surface emitters according to various aspects;

[0012] FIG. 4 shows a flow diagram of a method for manufacturing surface emitters according to various aspects, and FIG. 5 shows schematic cross-sectional views of the manufacturing process of the surface emitters according to various aspects;

[0013] FIG. 6 shows a flow diagram of a method for manufacturing surface emitters according to various aspects, and FIG. 7 shows schematic cross-sectional views of the manufacturing process of the surface emitters according to various aspects;

[0014] FIG. 8A shows a schematic cross-sectional view of a surface emitter according to various aspects, and FIG. 8B shows aspects of the manufacturing method for setting up the output side of the surface emitter; and

[0015] FIG. 9A to FIG. 11 each show aspects in the manufacturing process of the surface emitters according to various aspects. The following detailed description refers to the accompanying drawings, which, for illustrative purposes, show specific details and aspects in which the disclosure may be practiced. Various aspects are described with respect to a surface emitter, and various aspects are described with respect to a method of manufacturing a surface emitter. It is understood that aspects described in connection with the method may also apply to the surface emitter, and vice versa. In the drawings, like or similar elements, features, and structures are represented by like reference numerals.Please note that the drawings serve to illustrate various aspects of the surface emitter and its fabrication and are not necessarily drawn to scale.

[0016] FIG. 1A to FIG. 1E each show a schematic cross-sectional view of a surface emitter 100 according to various aspects. In general, the surface emitter 100 may include a light-emitting structure 102, which may be arranged between a first (e.g., dielectric) mirror structure 104 and a second (e.g., dielectric) mirror structure 106. The light-emitting structure 102 may be configured to emit light (e.g., in the direction of the first mirror structure 104 or the second mirror structure 106). The first mirror structure 104 and the second mirror structure 106 may be configured to reflect the light emitted by the light-emitting structure 102. The first mirror structure 104 and / or the second mirror structure 106 may (each) comprise a Bragg mirror or be designed as a Bragg mirror.For example, the first mirror structure 104 and the second mirror structure 106 may be configured as a distributed Bragg reflector (DRB).

[0017] The light-emitting structure 102 may include one or more epitaxially grown layers. For example, the light-emitting structure 102 may be formed as a stack of epitaxially grown layers. The light-emitting structure 102 configured to emit light may also be referred to as an active structure and / or an active region.

[0018] The first mirror structure 104, the light-emitting structure 102, and the second mirror structure 106 may form an optical cavity. The optical cavity may be configured such that the surface emitter 100 emits light of a predetermined frequency. The light emitted by the surface emitter 100 in the emission direction may be linearly polarized. A polarization direction of the light may be substantially perpendicular to a surface of the light-emitting structure 102.

[0019] The light-emitting structure 102 can have quantum wells for generating the light. A quantum well can be understood as a potential curve that allows a particle to move freely in one spatial dimension (e.g., perpendicular to an extension of the light-emitting structure 102), whereby the particle can only assume discrete (potential) energy values. This can be made possible, for example, by arranging a semiconductor layer with a first band gap between two other semiconductor layers with a second band gap, wherein the first band gap is smaller than the second band gap.

[0020] At least a portion of the light emitted by the surface emitter 100 may be coherent. The emission color of the light emitted by the surface emitter 100 may depend on the design of the light-emitting structure 102. Thus, the emission color of the emitted light can be adjusted during production. A wavelength of the emitted light can generally comprise electromagnetic radiation in the spectrum (invisible to the human eye) (e.g., in the ultraviolet spectrum, UV, or in the infrared range, IR) or in the visible spectrum (e.g., red, green, or blue). The light-emitting structure 102 may comprise a correspondingly suitable optoelectronic III / V or II / VI semiconductor material system, such as, for example, an aluminum gallium nitride / indium gallium nitride (AlGaN / InGaN).

[0021] Material system for blue light, green light and / or ultraviolet light, a

[0022] Aluminum gallium arsenide / indium gallium aluminum arsenide

[0023] (AlGaAs / InGaAlAs ) material system for infrared light , a

[0024] Aluminum gallium indium phosphide (AlGaInP) material system for red light, etc. In various aspects, the light-emitting structure 102 described herein comprises an Al x In y Gai- x-y N

[0025] (with 0 < x < 1 and 0 < y < 1 ) based material system on .

[0026] As described herein, the first mirror structure 104 and the second mirror structure 106 can be configured to reflect the light emitted by the light-emitting structure 102. According to various aspects, the first mirror structure 104 and / or the second mirror structure 106 can each have a plurality of (e.g., alternating) (dielectric) mirror layers with different refractive indices (which are configured, for example, as Bragg mirrors). Illustratively, the first mirror structure 104 can have a plurality of first mirror layers (e.g., a number N of first mirror layers (where N is an integer greater than or equal to two)) and the second mirror structure 106 can have a plurality of second mirror layers (e.g., a number M of second mirror layers (where M is an integer greater than or equal to two). A thickness of the mirror layers can, for example, be approximately a quarter of the wavelength, λ, of the emitted light.According to various aspects, the mirror layers of the first mirror structure 104 may be non-epitaxial mirror layers. In some aspects, the mirror layers of the second mirror structure 106 may additionally be non-epitaxial mirror layers.

[0027] The surface emitter 100 can be configured to be electrically contactable vertically, for example with contacts on opposite sides of the active region (i.e., the light-emitting structure 102), or horizontally, for example with contacts on a common side. According to various aspects, the light-emitting structure 102 can be arranged (vertically) between at least one n-type contact layer (for example, an n-doped semiconductor layer) and at least one p-type contact layer (for example, a p-doped semiconductor layer) (and, for example, in direct contact with them).

[0028] A contact layer described herein (e.g. the n-contact layer and / or the p-contact layer) may be configured to electrically contact the light-emitting structure 102. For example, the contact layer may be formed from a light-transmitting (i.e. transparent to the light emitted by the light-emitting structure 102) conductive material, such as a transparent conductive oxide (TCO), for example from indium tin oxide (ITO). Alternatively or additionally, the contact layer may be formed as a tunnel electrode or have such a tunnel electrode.

[0029] The p-contact layer and / or the n-contact layer can be arranged such that at least a portion of the light-emitting structure 102 is exposed, forming an aperture (opening). This (electrical and / or optical) aperture can enable beam shaping of the surface emitter 100 perpendicular to an extension of the light-emitting structure 102.

[0030] The surface emitter 100 may optionally comprise a substrate 108. The first mirror structure 104, the light-emitting structure 102 and the second mirror structure 106 may be arranged (e.g., in this order) above the substrate 108. The first mirror structure 104, the light-emitting structure 102 and / or the second mirror structure 106 may be arranged substantially parallel to a surface of the substrate 108. The substrate 108 may, for example, comprise or be a (semiconductor) wafer (in some aspects also referred to as a carrier wafer). According to various aspects, the light-emitting structure 102 may comprise an epitaxial structure (e.g., an epitaxial layer) 110, which may, for example, comprise Al x In y Gai- x-yN with 0 < x < 1 and 0 < y < 1 (e.g., aluminum indium gallium nitride, aluminum nitride (AIN), aluminum indium nitride (AlInN), indium nitride (InN), etc.). According to various aspects, at least the portions of the epitaxial structure disposed directly above the first mirror structure 104 may be comprised essentially of Al x In y Gai- x-y N. The light-emitting structure 102 may further comprise one or more surface emitter structural elements 112.

[0031] With reference to FIG.1B to FIG.1E, the surface emitter 100 may include a structural element (e.g., a ridge) by means of which the epitaxial structure 110 and the substrate 108 are in direct physical contact. In some embodiments, the substrate 108 may include a ridge 114 that is in direct physical contact with the epitaxial structure 110 (see, for example, FIG.1B and FIG.1D). In other embodiments, the epitaxial structure 110 may include a ridge 116 that is in direct physical contact with the substrate 108 (see, for example, FIG.1C and FIG.1E). In various embodiments, the epitaxial structure 110 may include the ridge 116 and the substrate 108 may include the ridge 114, and the ridges 114, 116 may be in direct physical contact with each other.

[0032] In some embodiments, the first mirror structure 104 and the substrate (in direction 11) may be arranged at a distance from each other such that a gap (e.g., an air gap) 113 is formed between them (see, for example, FIG. 1D and FIG. 1E). Alternatively, the first mirror structure 104 and the substrate 108 may be arranged in direct physical contact with each other.

[0033] In the following, methods 200, 400, 600 are described which comprise the production of such a surface emitter 100 with a first mirror structure 104 made of non-epi tactile

[0034] Mirror layers enabled.

[0035] FIG. 2 shows a flow diagram of a method 200 for manufacturing surface emitters according to various aspects. FIG. 3A and FIG. 3B show schematic cross-sectional views of the manufacturing method 200 according to various aspects.

[0036] The method 200 may include (in 202) providing a

[0037] substrate structure 300.

[0038] The substrate structure 300 may include a substrate 302 with a plurality of recesses 306 and a plurality of ridges 304. A portion of the substrate 302 may form the substrate 108 of the surface emitter 100. FIG. 3A shows a section in a schematic cross-sectional view. Each ridge 304 of the plurality of ridges may be arranged between two immediately adjacent recesses (e.g., a first recess 306(1) and a second recess 306(2)) of the plurality of recesses 306. For example, the ridge 304 may separate the first recess 306(1) and the second recess 306(2) from each other. The ridge 304 (or at least a portion of the ridge 304) may form the ridge 114.

[0039] The substrate structure 300 may include a plurality of epitaxial layers 308. As shown in the figures, each epitaxial layer 308 may be arranged (directly) above the ridge 304 (and in direct physical contact therewith) and may extend in the lateral direction (in direction 13 and opposite direction 13, i.e., in both lateral directions) beyond the ridge 304 such that each of the two immediately adjacent recesses forms a respective gap between the epitaxial layer 308 and the substrate 302. Illustratively, the first recess 306(1) may form a first gap 307(1) between the epitaxial layer 308 and the substrate 302, and the second recess 306(2) may form a second gap 307(2) between the epitaxial layer 308 and the

[0040] substrate 302. Each epitaxial layer 308 may comprise Al x In y Gai- x-yN (with 0 < x < 1 and 0 < y < 1). The substrate 302 may, for example, comprise (or consist of) gallium nitride, silicon, or sapphire (Al2O3). In some aspects, the substrate 302 may be made of gallium nitride, and each epitaxial layer 308 may also comprise GaN (e.g., the wings may consist essentially of GaN). In other aspects, the substrate 302 may be made of a different material (e.g., silicon or sapphire), and in this case, at least the portions of the epitaxial layer 308 that are not directly disposed above the ridge 304 may be made of GaN. For example, in this case, the epitaxial layer 308 may include one or more buffer layers directly above the ridge 304 that ensure epitaxial growth of GaN.In this case, the section of the epitaxial layer 308 which is arranged directly above the web 304 can be defect-rich and the lateral, free-standing regions of the epitaxial layer 308 can be defect-poor.

[0041] Illustratively, the epitaxial layer 308 may have two wings extending in lateral directions away from the web 304. The substrate structure 300 may therefore also be referred to as a cantilever substrate structure.

[0042] It is understood that the epitaxial layer / structure described herein is Al x In y Gai- x-y N (where 0 < x < 1 and 0 < y < 1). The surface emitter structure 314 described herein may, for example, comprise one or more layers of aluminum and / or indium.

[0043] According to various aspects, providing the substrate structure 300 may include forming the substrate structure. Here, a substrate may be patterned to form the plurality of recesses (see, for example, 552 in FIG. 5). Subsequently, an inhibitor layer 310 may be formed over the surfaces of each recess, which inhibitor layer is configured to prevent a growth of GaN. Therefore, the inhibitor layer 310 may also be referred to as a mask. Subsequently, the epitaxial layer 308 may be formed by means of an ELOG method (which, due to the inhibitor layer 310, is only formed over the uncovered fin 304 and extends in the lateral direction). In this ELOG method, a substantially lateral, epitaxial growth of the layer may take place.

[0044] Therefore, in some aspects, the substrate structure 300 may include the inhibitor layer 310. In other aspects, the inhibitor layer 310 may be removed or removed (e.g., as part of the method 200). For example, the method 200 may include wet-chemical removal of the inhibitor layer 310 (also referred to as a growth inhibitor layer). In this way, the height of the gaps 307 (1), 307 (2) may be adjusted (e.g., increased).

[0045] Aspects of a method for forming the substrate structure 300 are described, for example, in Kawaguchi et al.: "100 pm-Cavity GaN-Based Edge Emitting Laser Diodes by the Automatic Cleavage Technique Using GaN-on-Si Epitaxial Lateral Overgrowth", Crystal Growth Design, 2023, 23, 3572-3578.

[0046] Optionally, the method 200 may include etching back the epitaxial layer 308 to a desired thickness. However, this thickness may also be adjusted directly during the growth of the epitaxial layer 308, so that no etching back is required.

[0047] The method 200 may include (in 204) forming a plurality of surface emitter features (see 354, 356) by forming at least one surface emitter feature over a top side of at least one (e.g., each) epitaxial layer 308 facing away from the substrate 302. The surface emitter feature may, for example, include forming a layer stack 312 of active epitaxial layers and a p-doped layer. The surface emitter feature may, for example, include forming a surface emitter structure 314, which may, for example, include one or more epitaxial layers (e.g., a current aperture, a transparent current spreading layer, and / or a ring contact).

[0048] According to various aspects, the surface emitter structural elements 312, 314 may include at least one layer comprising aluminum and / or indium.

[0049] The method 200 may include (in 206) forming a mirror structure 316 at least over the plurality of surface emitter features 312, 314 and over exposed portions of a bottom surface of each epitaxial layer 308 facing the substrate 302 (see 358A in FIG. 3A and 358B in FIG. 3B). According to various aspects, the mirror structure 316 may include a plurality of non-epitaxial mirror layers. The mirror layers may each be formed using atomic layer deposition (ALD), for example. For example, the mirror structure 316 formed using ALD may conformally reshape the epitaxial structure 310.

[0050] In some embodiments (as shown in 358B in FIG. 3B), the mirror structure 316 can be formed such that the gaps 307 (1), 307 (2) between each epitaxial layer 308 and the substrate 302 are (substantially) completely filled (i.e., no gap remains). By completely filling the gaps 307 (1), 307 (2), the mechanical stability of the surface emitters can be increased. This can, for example, reduce the risk of breakage of the GaN wings during subsequent manufacturing processes. In this case, the thickness of the first mirror structure 104 and the height of the gap (in direction 11) can be coordinated.

[0051] In other embodiments (as shown in 358A in FIG.3A), the mirror structure 316 may be formed such that a portion of the respective gap 307 (1), 307 (2) remains between the mirror structure 316 and the substrate 302.

[0052] FIG.8A shows a section 802 of the structure thus formed.

[0053] According to various aspects, at least a portion of the exposed portions of the underside of the epitaxial layer 308 facing the substrate 302 may form the first mirror structure 104. According to various aspects, the mirror structure 316 formed over the top side of the epitaxial layer 308 may be modified to define the light output side.

[0054] Thus, in one embodiment, the method 200 may comprise forming one or more additional mirror layers 804 at least over portions disposed (directly) above the plurality of surface emitter features 312, 314 (see 852 in FIG. 8B). In this case, the mirror structure 316 and the one or more additional mirror layers 804 may form the second mirror structure 106. In this case, the surface emitter 100 may be a backside emitting surface emitter (VCSEL). For example, the mirror structure 316 may be formed such that it has a reflectivity (e.g., approximately 99.00%), and the one or more additional mirror layers 804 may increase the reflectivity on the top side (e.g., to approximately 99.99%).

[0055] In another embodiment, the method 200 may comprise at least partially removing (e.g., etching) one or more than one mirror layer of the plurality of mirror layers of the mirror structure 316, at least in sections that are arranged (directly) above the plurality of surface emitter structural elements 312, 314 (see 854 in FIG. 8B). In some embodiments, at least one of the mirror layers may be completely removed. In this way, the remaining M mirror layers may form the second mirror structure 106. In other embodiments, only a portion of a (topmost) mirror layer may be removed (i.e., its layer thickness may be reduced). In these cases, the surface emitter 100 may be a top-emitting surface emitter (VCSEL). For example, the mirror structure 316 may be formed such that it has a reflectivity (e.g.,approximately 99.99%) and by at least partially removing at least one mirror layer on the top side, the reflectivity on the.

[0056] top side (e.g. to approximately 99.00%).

[0057] Illustratively, the output side (i.e., the emission direction) of the surface emitters can be adjusted starting from the mirror structure 316, which is manufactured in a single process. Illustratively, the first mirror structure 104 and the second mirror structure 106 can have different reflectivities from one another.

[0058] FIG. 4 shows a flow diagram of a method 400 for manufacturing surface emitters (e.g., surface emitter 100) according to various aspects. To illustrate method 400, reference is made below to the schematic cross-sectional views of the surface emitter manufacturing process shown in FIG. 5.

[0059] The method 400 may include (in 402) structuring (552) a substrate 502 such that the substrate 502 has a plurality of recesses 504 and a plurality of ridges 506. As described above for the plurality of recesses 306 and the plurality of ridges 304, each ridge 506 of the plurality of ridges may be arranged between two immediately adjacent recesses 504 (1), 504 (2) of the plurality of recesses (e.g., separating them from one another).

[0060] The method 400 may include (in 404) forming (see 554) a portion of a first mirror structure 508 (e.g., by means of ALD) in each recess 504 (1), 504 (2) of the plurality of recesses of the substrate 502. The mirror layers of the first mirror structure 508 may be non-epitaxial (e.g., formed by means of ALD, CVD, or PVD) mirror layers.

[0061] The method 400 may include (in 406) forming a plurality of epitaxial layers 510 comprising Al x In y Gai- x-y N (with 0 < x < 1 and 0 < y < 1) using a method for epitaxial lateral overgrowth. In this way, each epitaxial layer can be arranged (directly) above the ridge 506 and extend in the lateral direction beyond the ridge 506 (as described above for the epitaxial layer 308). The non-epitaxial mirror layers of the first mirror structure 508 can prevent growth of GaN thereon, so that the epitaxial layer is formed only starting from the ridge 506. Illustratively, the first mirror structure can function as an inhibitor layer.

[0062] It is understood that there is a lateral distance (in direction 13) between two immediately adjacent epitaxial layers of the plurality of epitaxial layers 510 (otherwise, it would be a single epitaxial layer and not a plurality). Clearly, none of the epitaxial layers 510 has direct physical contact with another of the epitaxial layers 510. Consequently, the process parameters can be selected such that the ELOG process is terminated before the immediately adjacent epitaxial layers 510 coalesce.

[0063] In some embodiments, the portions of the first mirror structure 508 may be formed such that each portion (substantially) completely fills the associated recess 504 (Fig. 1), 504 (Fig. 2). It is understood that forming a layer as described herein may include multiple process steps, such as coating to form a preliminary layer and then removing a portion of the preliminary layer to form the layer.

[0064] In other embodiments, the sections of the first mirror structure 508 may be formed such that their height (in direction 11) is smaller than the height of the ridge 506. In this way, after forming the epitaxial layer 510, a gap may remain between the epitaxial layer 510 and the first mirror structure 508. In this case, the method 400 may comprise forming one or more additional mirror layers in this gap to completely fill it. In some embodiments, the gap may be substantially completely filled. In this case, the mirror layers of the first mirror structure 508 and the one or more additional mirror layers may form the first mirror structure 104. In other embodiments, (at least) a portion of the gap may be filled. For example, a gap entrance may be filled and a portion of the gap may remain (e.g., as a sealed air hole).In this case, a portion of the gap may remain. This can also increase the mechanical stability of the structure.

[0065] The method 400 may include (in 408) forming the plurality of surface emitter features 312, 314 by forming at least one surface emitter feature 312, 314 over the top side of at least one (e.g., each) epitaxial layer 510 facing away from the substrate 502 (as described above).

[0066] The method 400 may include (in 410) forming a second mirror structure 512 over the plurality of surface emitter features 312, 314 (e.g., by means of ALD).

[0067] FIG. 6 shows a flow diagram of a method 600 for manufacturing surface emitters (e.g., surface emitter 100) according to various aspects. To illustrate method 600, reference is made below to the schematic cross-sectional views of the surface emitter manufacturing process shown in FIG. 7. Method 600 may be similar to method 400, but method 600 does not require structuring of the substrate.

[0068] The method 600 may include (in 602) forming (752) a first mirror structure 704 (e.g., by means of ALD) having a plurality of sections over a (e.g., non-structured, e.g., planar) substrate 702. The first mirror structure 704 may include a plurality of openings 706. In these openings 706, the substrate is not covered (i.e., exposed) by the first mirror structure 704. Clearly, each opening 706 of the plurality of openings may be arranged between two immediately adjacent sections 704 of the plurality of sections (e.g., separating them from one another).

[0069] Forming the first mirror structure 704 may, for example, comprise forming a plurality of mirror layers (directly) above the substrate 702 and then at least partially removing (e.g., etching) at least one mirror layer (e.g., partially removing a mirror layer or completely removing one or more than one mirror layer) in portions to form the openings 706.

[0070] The method 600 may include (in 604) forming (754) a plurality of epitaxial structures 708 over the substrate 702 using an epitaxial lateral overgrowth process. Each epitaxial structure 708 formed in this way may extend from the substrate 702 through the opening 706 and laterally over a respective portion of each of the two immediately adjacent portions of the first mirror structure 704. Each epitaxial structure 708 of the plurality of epitaxial structures 708 may comprise Al x In y Gai- x-y N (with 0 < x < 1 and 0 < y < 1) or consist of them.

[0071] The method 600 may include (in 606) forming the plurality of surface emitter features 312, 314 by forming at least one surface emitter feature 312, 314 over the top side of at least one (e.g., each) epitaxial structure 708 facing away from the substrate 702 (as described above).

[0072] It is understood that epitaxial structures may also be formed (e.g., on a wafer) on which no surface emitter features 312, 314 are formed. The method 600 may include (in 608) forming (756) a second mirror structure 710 over the plurality of surface emitter features 312, 314 (e.g., by means of ALD).

[0073] Clearly, in the method 600, the epitaxial structure 708 can provide the web.

[0074] As described herein, the substrate may have a plurality of recesses and a plurality of ridges, and a plurality of epitaxial layers may be formed. Here, two immediately adjacent epitaxial layers may be arranged at a distance from one another. As shown in FIG.9A and FIG.9B, a gap opening 902 may be arranged between two immediately adjacent epitaxial layers (in each case). As described herein, in some embodiments (e.g., of the method 200), a portion of the gap between the substrate and the epitaxial layer may remain after the formation of the mirror structure (see FIG.9A). In other embodiments, the gap may be or be at least partially (e.g., partially or completely) filled by the mirror structure. As shown in FIG.9A and FIG.As shown in Figure 9B, one or more of the methods 200, 400, 600 described herein may include (at 906) filling each gap opening 902 of the plurality of gap openings. For example, each gap opening 902 may be filled with a metallic material and / or a dielectric material.

[0075] material can be filled.

[0076] This can improve the mechanical stability of the structures (e.g., for subsequent process steps). The portion of the mirror structure arranged between the epitaxial layer and the substrate (e.g., the first mirror structure 104) can also be protected from processing (e.g., coating and / or etching) in subsequent process steps. Filling the gap openings 902 can comprise a lift-off-based method and / or active structuring. A spin-on glass-based and / or a benzocyclobutene (BOB)-based method can also be used for filling. According to various aspects, one or more of the methods 200, 400, 600 described herein can comprise contacting each surface emitter. FIG. 10 shows, for illustration purposes, an exemplary p-type contact 1002 (e.g., as contacting the p-type contact layer) and an exemplary n-type contact 1004 (e.g., as contacting the n-type contact layer).In this case, the p-contact 1002 and the n-contact 1004 can have any suitable design.

[0077] As shown in 1054 in FIG.10, the p-contact 1002 can be designed, for example, as a ring contact.

[0078] As shown at 1052 in FIG. 10, the n-type contact 1004 may be implemented from the top side. This may be achieved, for example, by vias (e.g., an etching into the n-doped region and filling the etching with an electrically conductive (e.g., metallic) material). It is understood that in this case, electrical insulation of the n- and p-doped layers (e.g., using passivation) may be ensured.

[0079] Alternatively, the n-contact 1004 can be arranged over the backside of the substrate, as shown at 1056 in FIG. 10. Illustratively, the n-contact 1004 can directly contact the electrically conductive substrate.

[0080] As shown in FIG. 11, one or more of the methods 200, 400, 600 described herein may include dicing (1100) into a plurality of surface emitters 100. The dicing may be performed, for example, by mechanical breaking (with optional prior scribing) and / or using a laser (e.g., stealth dicing). In this case, the epitaxial layers may be separated into individual components directly at the web or between individual components.

[0081] Optionally, the structure can be transferred to another

[0082] Substrate (e.g. using one or more than one adhesive layer). This can make handling of the

[0083] Improve structure.

[0084] The epitaxial GaN-based layers described herein can have a comparatively high material quality, thereby increasing the performance and aging stability of the surface emitters produced in this way. Furthermore, the cavity is significantly smaller (thinner) compared to processes in which the first mirror structure 104 is attached to the backside of the substrate, thereby reducing optical losses.

[0085] Various examples are provided below that describe one or more aspects of the surface emitter 100 and the method. It is understood that aspects described with respect to the surface emitter 100 may also apply to the method of manufacturing it, and vice versa. For example, elements of the surface emitter 100 may be formed in a corresponding manufacturing process.

[0086] Example 1 is a method for producing surface emitters, the method comprising: providing a substrate structure, comprising: a substrate with a plurality of depressions and a plurality of ridges, each ridge being arranged between two immediately adjacent depressions of the plurality of depressions (e.g., separating them from each other), and a plurality of epitaxial layers (which, for example, are Al x In y Gai- x-yN (with 0 < x < 1 and 0 < y < 1 ) or consist of; in one example, each epitaxial layer may consist essentially of gallium nitride and the surface emitter features may comprise one or more than one layer, of which at least one layer comprises aluminum and / or indium), wherein each epitaxial layer is arranged (directly) above a ridge of the plurality of ridges (and in direct physical contact therewith) and extends in a lateral direction beyond the ridge such that each of the two immediately adjacent recesses forms a respective gap between the epitaxial layer and the substrate; forming a plurality of surface emitter features by forming at least one surface emitter feature over a top side of at least one (e.g.of each) epitaxial layer; forming a mirror structure at least over the plurality of surface emitter features and over exposed portions of a substrate-facing underside of each epitaxial layer (e.g., by means of atomic layer deposition, ALD).

[0087] The columns can be used to illustrate the first

[0088] to form mirror structures 104.

[0089] Example 2 is set up according to Example 1, wherein the

[0090] Mirror structure is formed by atomic layer deposition.

[0091] Example 3 is configured according to example 1 or 2, wherein the mirror structure comprises a plurality of mirror layers; and wherein the method further comprises: at least partially removing (e.g., etching) at least one mirror layer of the plurality of mirror layers of the mirror structure (e.g., a partial removal of a mirror layer or a complete removal of one or more than one mirror layer) at least in portions disposed (directly) above the plurality of surface emitter features; or forming one or more than one additional mirror layer at least above the portions of the mirror structure.

[0092] Example 4 is configured according to any one of Examples 1 to 3, wherein the mirror structure is formed such that: it (substantially) completely fills the gaps between each epitaxial layer and the substrate; or a portion of the respective gap remains between the mirror structure and the substrate.

[0093] Example 5 is configured according to any one of Examples 1 to 4, wherein the mirror structure is formed such that a respective gap opening of a plurality of gap openings remains between two immediately adjacent epitaxial layers of the plurality of epitaxial layers; and wherein the method further comprises: filling each gap opening of the plurality of gap openings (e.g., with a metallic material or a dielectric material).

[0094] Example 6 is a method for producing surface emitters, the method comprising: structuring a substrate such that the substrate has a plurality of depressions and a plurality of ridges, wherein each ridge of the plurality of ridges is arranged between two immediately adjacent depressions of the plurality of depressions (e.g., separating them from each other); in each depression of the plurality of depressions of the substrate, forming a portion of a first mirror structure (e.g., by means of ALD) such that the portion (substantially) completely fills the depression; forming a plurality of epitaxial layers (which, for example, Al x In y Gai- x-yN (with 0 < x < 1 and 0 < y < 1) or consist of gallium nitride; in one example, each epitaxial layer may consist essentially of gallium nitride and the surface emitter features may comprise one or more layers, at least one of which comprises aluminum and / or indium), using a method for epitaxial lateral overgrowth such that each epitaxial layer is arranged (directly) above a ridge of the plurality of ridges and extends laterally beyond the ridge; forming a plurality of surface emitter features by forming at least one surface emitter feature over a top side of each epitaxial layer facing away from the substrate; and forming a second mirror structure over the plurality of surface emitter features (e.g. by means of ALD).

[0095] Example 7 is a method for producing

[0096] Surface emitters, the method comprising: forming a first mirror structure (e.g. by means of ALD) having a plurality of sections over a (e.g. non-structured, e.g. planar) substrate, wherein the first mirror structure has a plurality of openings (in which the substrate is not covered by the first mirror structure), wherein each opening of the plurality of openings is arranged between two immediately adjacent sections of the plurality of sections (e.g. separating them from each other); forming a plurality of epitaxial structures (which, for example, Al x In y Gai- x-yN (with 0 < x < 1 and 0 < y < 1); in one example, each epitaxial layer may consist essentially of gallium nitride and the surface emitter features may comprise one or more than one layer, at least one layer of which comprises aluminum and / or indium), over the substrate using a method for epitaxial lateral overgrowth such that each epitaxial structure extends (directly) from the substrate through an opening of the plurality of openings and in a lateral direction over a respective part of each of the two immediately adjacent sections; forming a plurality of surface emitter features by forming at least one surface emitter feature over a top side of at least one (e.g.each) epitaxial structure; and forming a second mirror structure over the plurality of surface emitter features (e.g., by ALD).

[0097] Example 8 is configured according to example 6 or 7, wherein the first mirror structure and / or the second mirror structure is formed by means of atomic layer deposition.

[0098] Example 9 is configured according to any one of Examples 6 to 8, wherein the second mirror structure comprises a plurality of mirror layers; and wherein the method further comprises: at least partially removing (e.g., etching) at least one mirror layer of the plurality of mirror layers of the mirror structure (e.g., a partial removal of a mirror layer or a complete removal of one or more than one mirror layer) at least in portions disposed (directly) above the plurality of surface emitter features; or forming one or more than one additional mirror layer at least above the portions of the second mirror structure.

[0099] Example 10 is configured according to any one of Examples 1 to 9, the method further comprising: singulating into a plurality of surface emitters.

[0100] Example 11 is configured according to any one of Examples 1 to 10, wherein the substrate comprises (or consists of) gallium nitride, silicon, or sapphire (A12O3).

[0101] Example 12 is a computer-readable medium (e.g., a computer program product, a non-transitory storage medium, a non-transitory storage medium, or a non-volatile storage medium) storing instructions that, when executed by a processor, cause the processor to control an apparatus to perform the method of any of Examples 1 to 11.

[0102] Example 13 is a control device comprising one or more than one processor configured to perform the method according to any one of Examples 1 to 11.

[0103] Example 14 is a surface emitter comprising: a substrate; a first mirror structure and a second mirror structure disposed above the substrate; a light-emitting structure disposed between the first mirror structure and the second mirror structure, wherein the light-emitting structure comprises a (e.g. Al x In y Gai- x-y N (with 0 < x < 1 and 0 < y < 1) epitaxial structure, wherein the first mirror structure is arranged between the substrate and the light-emitting structure and in direct physical contact with the epitaxial structure, and wherein the first mirror structure comprises a plurality of non-epitaxial mirror layers. Example 15 is configured according to Example 14, wherein (e.g., exactly) a portion of the epitaxial structure is arranged in direct physical contact with the substrate.

[0104] Example 16 is configured according to Example 15, wherein the surface emitter further comprises: a gap between the first mirror structure and the substrate.

[0105] Example 17 is configured according to Example 15, wherein the first mirror structure is arranged in direct physical contact with the substrate.

[0106] Various aspects relate to an epitaxial layer and / or forming an epitaxial layer. In general, an epitaxial layer can be formed on a crystalline substrate (e.g., another layer). An epitaxial layer can be understood to mean a layer in which at least one crystallographic orientation of a single crystal of the epitaxial layer corresponds to an orientation of the crystalline substrate. In general, an epitaxial layer can be understood to mean a substantially single-crystalline layer. According to various aspects, an epitaxial layer described herein can be a layer that is single-crystalline at least in the portion that forms a surface emitter (e.g., the surface emitter 100). Epitaxy can be analyzed (e.g., measured, confirmed), for example, by means of X-ray diffraction (XRD) (non-destructive) and / or by means of transmission electron microscopy (TEM).

[0107] An epitaxial layer can generally be formed, for example, by a physical vapor deposition process, PVD (e.g., molecular beam epitaxy (MBE), sputtering, for example, at a temperature above room temperature) and / or a chemical vapor deposition process, CVD (e.g., atomic layer deposition (ALD)). Such an epitaxial layer can therefore also be referred to as an epitaxially grown layer and / or an epitaxially formed layer. The word "exemplary" is used herein to mean "as an example, instance, or illustration." Any example or design described herein as "exemplary" is not necessarily to be understood as preferred or advantageous over other examples or designs.

[0108] A "control device" as used herein can be understood as any type of entity (e.g., implementing logic) that allows the processing of data or signals. The control device can, for example, comprise circuitry and / or (at least) one processor, which can execute software stored in a storage device (in some aspects also referred to as a storage medium), in firmware, or in a combination thereof, and can issue instructions based thereon. The control device can, for example, be configured by means of code segments (e.g., software) to control the operation of a system. For example, the data or signals can be handled according to at least one (i.e., one or more than one) specific function performed by the processor.A processor may include or be formed from an analog circuit, a digital circuit, a mixed-signal circuit, a logic circuit, a microprocessor, a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), a field-programmable gate array (FPGA), an integrated circuit, or any combination thereof. Any other type of implementation of the respective functions described in detail herein may also be understood as a processor or logic circuit. It is understood that one or more of the method steps described in detail herein may be carried out (e.g., realized) by a processor, through one or more specific functions performed by the processor. The processor may therefore be configured to carry out one of the methods described herein or its components for information processing.The words "multiple" and "several" in the description or claims expressly refer to a quantity greater than one.

[0109] The term "connected" can be understood in the sense of a (e.g., mechanical, optical, and / or electrical) connection and / or interaction, e.g., direct or indirect. For example, several elements can be connected mechanically, so that they are physically held (e.g., a plug connected to a socket), and electrically, so that they have an electrically conductive path (e.g., signal paths exist along a communicative

[0110] Chain ) .

[0111] In the above descriptions and the accompanying figures, various components of the surface emitter are depicted as separate elements. However, discrete optical functions may also be implemented as a single element. Similarly, a single element may be or become divided into two or more elements.

[0112] It is understood that the methods described herein are exemplary and can therefore be implemented in a corresponding device. It is also understood that implementations of the devices described herein can be implemented as a corresponding method.

[0113] Although the disclosure has been shown and described with reference to specific embodiments, it is understood that various changes in form and detail may be made without departing from the scope of the disclosure as defined by the appended claims. The scope of the disclosure is therefore indicated by the appended claims, and all changes which come within the meaning and range of equivalence of the claims are therefore intended to be embraced. LIST OF REFERENCE SYMBOLS 00: Surface emitter 02: Light-emitting structure 04: First mirror structure 06: Second mirror structure 08: Substrate 10: Epitaxial layer

[0114] 114, 116: Bridge

[0115] 113: Gap 00: Process 00: Substrate structure

[0116] 302, 502: Substrat

[0117] 304, 506: Bridge

[0118] 306, 504: Deepenings

[0119] 307 : Column

[0120] 308, 510, 708: epitaxial layer

[0121] 310: Inhibitor layer

[0122] 312: Layer stack

[0123] 314: Surface emitter structure

[0124] 400: Procedure

[0125] 508, 704: first mirror structure

[0126] 512, 710: second mirror structure

[0127] 600: Procedure

[0128] 706: Openings

[0129] 804: additional mirror layer

[0130] 902: Intermediate space opening

[0131] 1002: p-contacting

[0132] 1004: n-contacting

Claims

Patent claims 1. A method (200) for producing surface emitters (100), the method (200) comprising: • Providing (202) a substrate structure (300), comprising: o a substrate (302) having a plurality of depressions (306) and a plurality of webs (304), each web (304) being arranged between two immediately adjacent depressions (306(1), 306(2)) of the plurality of depressions, and o a plurality of epitaxial layers (308), each epitaxial layer (308) being arranged over a web (304) of the plurality of webs and extending in the lateral direction (13, -13) over the Web (304) extends such that each of the two immediately adjacent recesses (306(1), 306(2)) has a respective gap (307(1), 307 (2) ) between the epitaxial layer (308) and the substrate (302); • Forming (204) a plurality of surface emitter structural elements (312, 314) by forming at least one surface emitter structural element (312, 314) over an upper side of each epitaxial layer (308) facing away from the substrate (302); and • Forming (206) a mirror structure (316) at least over the plurality of surface emitter structure elements (312, 314) and over exposed portions of a bottom side of each epitaxial layer (308) facing the substrate (302).

2. Method (200) according to claim 1, wherein the mirror structure (316) is formed by means of atomic layer deposition.

3. The method (200) according to claim 1 or 2, wherein the mirror structure (316) comprises a plurality of mirror layers; and wherein the method (200) further comprises: • at least partially removing (854) at least one mirror layer of the plurality of mirror layers of the mirror structure (316) at least in sections arranged above the plurality of surface emitter structure elements; or • Forming (852) one or more than one additional mirror layer (804) at least over the portions of the mirror structure (316).

4. The method (200) according to any one of claims 1 to 3, wherein the mirror structure (316) is formed such that: • this completely fills the gap (307 (1), 307 (2)) between each epitaxial layer (308) and the substrate (302); or • a part of the respective gap (307 (1), 307 (2)) remains between the mirror structure (316) and the substrate (302).

5. Method (200) according to one of claims 1 to 4, • wherein the mirror structure (316) is formed such that between two immediately adjacent epitaxial layers (308) of the plurality of epitaxial layers a respective gap opening (902) of a plurality of gap openings (902) remains; and • wherein the method (200) further comprises: filling (906) each gap opening (902) of the plurality of gap openings.

6. A method (400) for producing surface emitters (100), the method comprising: • Structuring (402) a substrate (502) such that the substrate (502) has a plurality of recesses (504) and a plurality of webs (506), wherein each web (506) of the plurality of webs is arranged between two immediately adjacent recesses (504 (1), 504 (2)) of the plurality of recesses; • in each recess (504) of the plurality of recesses of the substrate, forming (404) a portion of a first mirror structure (508) such that the portion completely fills the recess (504); • forming (406) a plurality of epitaxial layers (510) using a method for epitaxial lateral overgrowth such that each epitaxial layer (510) is arranged over a ridge (506) of the plurality of ridges and extends in the lateral direction (13, -13) beyond the ridge (506); • Forming (408) a plurality of surface emitter structural elements (312, 314) by forming at least one surface emitter structural element over an upper side of each epitaxial layer (510) facing away from the substrate (502); and • Forming (410) a second mirror structure (512) over the plurality of surface emitter structure elements (312, 314).

1. A method (600) for producing surface emitters (100), the method (600) comprising: • Forming (602) a first mirror structure (704) having a plurality of sections over a substrate (702), wherein the first mirror structure (704) comprises a a plurality of openings (706), each opening (706) of the plurality of openings being arranged between two immediately adjacent sections of the plurality of sections; • Forming (604) a plurality of epitaxial structures (708) over the substrate (702) using a A method for epitaxial lateral overgrowth such that each epitaxial structure (708) extends from the substrate (702) through an opening (706) of the plurality of openings and in the lateral direction (13, - 13) over a respective part of each of the two immediately adjacent sections, wherein the epitaxial structures (708) have a light-emitting structure (102) above a contact layer, wherein the contact layer is formed from a semiconductor material; • Forming (606) a plurality of surface emitter structural elements (312, 314) by forming at least one surface emitter structural element over a top side of each epitaxial structure (708) facing away from the substrate (702); • forming (608) a second mirror structure (710) over the plurality of surface emitter structure elements (312, 314); and • Forming a via, which is connected to the contact layer, from a top side of the surface emitter structure.

8. Method (400, 600) according to claim 6 or 7, wherein the first mirror structure (508, 704) and / or the second mirror structure (512, 710) are atomic layer deposition.

9. Method (200, 400, 600) according to one of claims 1 to 8, further comprising singulating (1100) into a plurality of surface emitters (100).

10. The method (200, 400, 600) according to any one of claims 1 to 9, wherein the substrate (108, 302, 502, 702) is gallium nitride, silicon or sapphire.

11. Surface emitter (100) comprising: • a substrate (108, 302, 502, 702); • a first mirror structure (104, 508, 704) and a second mirror structure (106, 512, 710) arranged above the substrate (108, 302, 502, 702); • a light-emitting structure (102) which is arranged at least partially between the first mirror structure (104, 508, 704) and the second mirror structure (106, 512, 710), wherein the light-emitting structure (102) has an epitaxial structure (110, 308, 510, 708), wherein the first mirror structure (104, 508, 704) is arranged at least partially between the substrate (108, 302, 502, 702) and the light-emitting structure (102) and in direct physical contact with the epitaxial structure (110, 308, 510, 708), and wherein the first mirror structure (104, 508, 704) has a plurality of non-epitaxial mirror layers.

12. The surface emitter (100) of claim 11, wherein a portion of the epitaxial structure (110, 308, 510, 708) is arranged in direct physical contact with the substrate (108, 302, 502, 702).

13. Surface emitter (100) according to claim 12, further comprising: • a gap between the first mirror structure (104, 508, 704) and the substrate (108, 302, 502, 702).

14. The surface emitter (100) of claim 13, wherein the first mirror structure (104, 508, 704) is arranged in direct physical contact with the substrate (108, 302, 502, 702).

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