Surface emitters and methods for manufacturing a surface emitter

Abstract

A surface emitter (100) and a method (300, 400) for producing a surface emitter (100) are disclosed, wherein the surface emitter (100) in one embodiment comprises: a substrate (108); a first mirror structure (104) and a second mirror structure (106) arranged above the substrate (108); a light-emitting structure (102) arranged between the first mirror structure (104) and the second mirror structure (106), wherein the light-emitting structure (102) is configured to emit light, and wherein the first mirror structure (104) and the second mirror structure (106) are configured to reflect the light emitted by the light-emitting structure (102); and a lattice structure (110) comprising a plurality of periodically arranged lattice elements (112) embedded in the substrate (108), wherein the lattice structure (110) is configured to polarize the emitted light.

Description

[0001] Various embodiments relate to a surface emitter (vertical cavity surface emitting laser, VCSEL) and a method for its production.

[0002] 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. In a surface emitter, a light-emitting active region, formed by epitaxial growth, is typically arranged vertically between two distributed Bragg reflectors (DBRs).

[0003] Various applications of surface emitters can be polarization-sensitive, such as timers, gyroscopes, magnetometers, optical mice, etc. For these applications, a stable, linear polarization of the light emitted by the surface emitter may be required and / or desirable. However, even small changes in the operating conditions of the surface emitter can cause an abrupt polarization switch from a polarization state oriented in a first direction to a second direction opposite (orthogonal) to the first direction, such as changes in modal gain, phase anisotropy in the presence of birefringence, the appearance of higher-order transverse modes, etc.

[0004] Various aspects relate to a surface emitter and a method for its manufacture to stabilize the polarization of the emitted light in order to prevent, for example, polarization switching.

[0005] This is made possible, for example, by the surface emitter having an embedded grating structure configured to stabilize the polarization of the emitted light. In some embodiments, the grating structure can be embedded in a substrate of the surface emitter (outside an optical cavity of the surface emitter). In this way, polarization switching can be prevented, for example, in a back-emitting surface emitter. In other embodiments, the grating structure can be embedded in an epitaxial layer arranged within the optical cavity. In this way, for example, inherent polarization stabilization can be achieved.

[0006] In general, a surface emitter can have a plurality of epitaxial layers arranged one above the other (e.g., as part of the light-emitting active region or one of the Bragg mirrors). For the production of such an epitaxial layer, it may be necessary for the underlying layer to also be an epitaxial layer. In various aspects, it has been recognized that a grating structure can be arranged below the optical cavity or within the optical cavity if it is or will be embedded in an epitaxial layer. In this way, a grating structure can be used for polarization stabilization for both back-emitting surface emitters and top-emitting surface emitters. For example, the grating structure can also be used if a side of the substrate opposite the optical cavity is structured (e.g., into a three-dimensional (3D) lens).The surface emitter 100 described herein can, for example, enable polarization stabilization in a temperature range from approximately -40°C to approximately 150°C (or an even wider temperature range). Embedding the grating structure in an epitaxial layer can ensure epitaxial growth of a layer formed thereon. Clearly, embedding the grating structure can improve the properties of the surface emitter (which depend on the epitaxial growth of the layers) compared to forming the grating structure between two other layers.

[0007] In the drawings, like reference characters generally refer to the same parts throughout the several views. The drawings are not necessarily to scale, 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: Fig. 1 to Fig. 1F each show a schematic cross-sectional view of a surface emitter according to various aspects; Fig. 2A to Fig. 2C each show an exemplary embodiment of a lattice structure according to various aspects; Fig. 3 shows a flow diagram of a method for manufacturing a surface emitter according to various aspects; Fig. 4 shows a flow diagram of a method for manufacturing a surface emitter according to various aspects; and Fig. 5 shows schematic cross-sectional views in the manufacturing process of a surface emitter according to various aspects.

[0008] The following detailed description refers to the accompanying drawings, which, for purposes of illustration, 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. It is understood that the drawings serve to illustrate various aspects of the surface emitter and its manufacture and are not necessarily drawn to scale.

[0009] Fig. 1A to Fig. 1F 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., toward 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) include a Bragg mirror or be configured 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).

[0010] The surface emitter 100 described herein may be a top-emitting surface emitter (VCSEL) or a backside-emitting surface emitter (VCSEL). This may define an emission direction of the surface emitter 100. In this case, the first mirror structure 104 and the second mirror structure 106 may have a (slightly) lower reflectivity than the other. For example, the first mirror structure 104 may have a first reflectivity and the second mirror structure 106 may have a second reflectivity different from the first reflectivity. In one example, the second reflectivity may be lower, so that light emitted in the direction of the first mirror structure 104 is reflected therefrom in the direction of the second mirror structure 106, and a portion of the light may pass through the second mirror structure 106 and thus be coupled out of the surface emitter 100.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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 manufacturing. A wavelength of the emitted light may generally comprise electromagnetic radiation in the non-visible (to the human eye) spectrum (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 an aluminum gallium nitride / indium gallium nitride (AlGaN / InGaN) material system for blue light, green light and / or ultraviolet light, an aluminum gallium arsenide / indium gallium aluminum arsenide (AlGaAs / InGaAlAs) material system for infrared light, an aluminum gallium indium phosphide (AlGaInP) material system for red light, etc.

[0015] 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., mirror layer pairs) (e.g., a number M of second mirror layers (where M is an integer greater than or equal to two).For example, a thickness of the mirror layers can be approximately a quarter of the wavelength, λ, of the emitted light.

[0016] 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 (and, for example, in direct contact with) at least one n-type contact layer (e.g., an n-doped semiconductor layer) and at least one p-type contact layer (e.g., a p-doped semiconductor layer).

[0017] A contact layer described herein (e.g., the n-type contact layer and / or the p-type 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, indium tin oxide (ITO). Alternatively or additionally, the contact layer may be configured as or comprise a tunnel electrode.

[0018] The p-type contact layer and / or the n-type contact layer can be arranged such that at least a portion of the light-emitting structure 102 is exposed, thereby 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.

[0019] The surface emitter 100 may include 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, include or be a (semiconductor) wafer (in some aspects also referred to as a carrier wafer). For example, the wafer may be made of gallium arsenide. Optionally, a buffer layer may be arranged between the substrate 108 and the first mirror structure 104. In some embodiments, the buffer layer may also be part of the substrate 108 (i.e., the substrate 108 may include the buffer layer). In various embodiments, the buffer layer may be made of gallium arsenide. Optionally, the substrate 108 (e.g.,on its surface facing the light-emitting structure 102) have one or more than one other (e.g. epitaxially grown) structure (e.g. layer or layer stack), such as a photodiode configured for monitoring.

[0020] The light emitted by the surface emitter 100 in the emission direction can be linearly polarized. A polarization direction of the light can be substantially perpendicular (to the propagation direction of the light). The surface emitter 100 can have a grating structure 110. The grating structure 110 can be configured to stabilize the polarization of the emitted light. The grating structure 110 can have a plurality of periodically arranged grating elements 112.

[0021] A lattice structure as described herein can be understood as a regular arrangement of (e.g. evenly spaced) lattice elements.

[0022] Exemplary embodiments of the lattice structure 110 are shown in Fig. 2A to Fig. 2C. The grid elements 112 of the grid structure 110 can, for example (see Fig. 2A) have a plurality of lines arranged side by side so that the light emitted by the light-emitting structure 102 can pass through a gap between adjacent lines of the grating structure 110. It is understood that these are exemplary embodiments of the grating structure 110 and that the grating structure 110 may also have any other arrangement of grating elements 112 to break the (rotational) symmetry of the surface emitter resonator and / or the polarization-independent reflectivity of the first mirror structure 104 and / or second mirror structure 106.

[0023] As described herein, the substrate 108 may be a wafer, or a wafer may include the substrate 108. According to various aspects, a plurality of surface emitters 100 may be arranged on the substrate 108. In some aspects, the grating structure 110 may be formed along an entire surface of the wafer. In other aspects, the grating structure 110 may be arranged exclusively in the regions where a respective surface emitter 100 is formed.

[0024] The grating structure 110 (e.g., each grating element of the plurality of periodically arranged grating elements 112) may comprise or consist of a material having a refractive index that is at least 0.1 (e.g., at least 0.5, e.g., at least 1.0) greater (or smaller) than a refractive index of the first mirror structure 104 and / or the second mirror structure 106. A refractive index of a mirror structure may be an average refractive index.

[0025] According to various aspects, the lattice structure 110 may include or consist of a dielectric material, such as silicon oxide (SiO2), silicon nitride (Si x N y ), aluminum oxide (Al2O3), or titanium oxide (TiO2). In other embodiments, the lattice structure 110 may comprise or consist of a semimetal. In yet other embodiments, the lattice structure 110 may comprise or consist of a semiconductor material or a semimetal.

[0026] As in Fig. 1A, the grid structure 110 may, for example, be embedded in the substrate 108. Consequently, the grid structure 110 may be completely surrounded by the substrate 108. An exemplary method 300 for embedding the grid structure 110 in the substrate 108 is described with reference to Fig. 3 described.

[0027] In this case, a distance between two adjacent grating elements of the plurality of periodically arranged grating elements 122 can be in a range of approximately 0.1⋅λ4 to approximately 10 λ (where λ is the wavelength of the emitted light). A thickness of each grating element of the plurality of periodically arranged grating elements 112 may be in a range from approximately 0.01 λ to approximately 10 λ.

[0028] As in Fig. 1B to Fig. 1F, the grating structure 110 (e.g., the plurality of periodically arranged grating elements 112) may be embedded in an epitaxial layer 114.

[0029] In some embodiments, the epitaxial layer 114 may be arranged outside the optical cavity, e.g., between the substrate 108 and the first mirror structure 104 (see Fig. 1B) (and optionally in direct physical contact with them). Alternatively, the epitaxial layer 114 may be arranged above (e.g., directly on) the second mirror structure 106.

[0030] The arrangement of the grating structure 112 outside the optical cavity can, for example, be particularly advantageous for a back-emitting surface emitter 100, since in this case the reflectivity of the first mirror structure 104 is lower than the reflectivity of the second mirror structure 106 and thus an influence of the grating structure 110 through the first mirror structure 104 is stronger, whereby the polarization stabilization is increased.

[0031] In other embodiments, the epitaxial layer 114 may be disposed within the optical cavity. In a first example, the epitaxial layer 114 may be disposed between (and optionally in direct physical contact with) the first mirror structure 104 and the light-emitting structure 102 (see Fig. 1C). In a second example, the epitaxial layer 114 may be arranged between (and optionally in direct physical contact with) the light-emitting structure 102 and the second mirror structure 106 (see Fig. 1D). In a third example, the epitaxial layer 114 may be arranged between (and optionally in direct physical contact with) two consecutive mirror layers of the plurality of mirror layers of the first mirror structure 104 (see Fig. 1E). Illustratively, a first part 104(1) of the plurality of mirror layers with a number of Nx mirror layers can be arranged below the first mirror structure 104 and a second part 104(2) of the plurality of mirror layers with a number of x mirror layers can be arranged above the first mirror structure 104 (where x is greater than or equal to one, e.g., in Fig. 1E N=6 and x=2). In a fourth example, the epitaxial layer 114 may be arranged between (and optionally in direct physical contact with) two consecutive mirror layers of the plurality of mirror layers of the second mirror structure 106 (see Fig. 1F). Illustratively, a first part 106(1) of the plurality of mirror layers with a number of My mirror layers can be arranged below the second mirror structure 106 and a second part 106(2) of the plurality of mirror layers with a number of y mirror layers can be arranged above the second mirror structure 106 (where y is greater than or equal to one, e.g., in Fig. 1F M=6 and y=3).

[0032] According to various aspects (e.g., when the grating structure 110 is arranged in the optical cavity), a distance, d, between two adjacent grating elements of the plurality of periodically arranged grating elements 122 may correspond approximately to an integer multiple of a quarter wavelength of the emitted light (i.e. d=p⋅λ4, where p is an integer greater than or equal to one). To ensure the properties of the surface emitter 100, it may be necessary, for example when the grating structure 110 is arranged in the optical cavity, for a defect density (at least in a surface region) of the epitaxial layer 114 to be less than 1 10 9 cm -2 (e.g. less than 1·10 7 cm -2 , e.g. less than 1·10 5 cm -2 ). This can be achieved, for example, by the method described herein using epitaxial lateral overgrowth. The defect density can indicate a number of defects per square centimeter.

[0033] In various aspects, the epitaxial layer 114 described herein may be comprised of a semiconductor material.

[0034] Fig. 3 shows a flow diagram of a method 300 for manufacturing a surface emitter (e.g., the surface emitter 100 according to the method described in Fig. 1A) according to various aspects.

[0035] Method 300 may include (at 302) forming a grating structure (directly) on a substrate. The grating structure may include a plurality of periodically arranged grating elements.

[0036] The method 300 may include (at 304) forming an epitaxial layer over the substrate and the grating structure using a lateral epitaxial overgrowth method. In this way, the plurality of periodically arranged grating elements of the grating structure can be embedded. The substrate and the epitaxial layer may be made of the same material. Illustratively, the grating structure can thereby be embedded into the substrate.

[0037] The method 300 may include (in 306) forming a first mirror structure over (e.g., directly on) the epitaxial layer.

[0038] Method 300 may include (in 308) forming a light-emitting structure over (e.g., directly on) the first mirror structure. The light-emitting structure may be configured to emit light.

[0039] Method 300 may include (in 310) forming a second mirror structure over (e.g., directly on) the light-emitting structure. The first mirror structure and the second mirror structure may be configured to reflect the light emitted by the light-emitting structure.

[0040] The grating structure can be configured to stabilize the polarization of the emitted light.

[0041] Fig. 4 shows a flow diagram of a method 400 for manufacturing a surface emitter (e.g., the surface emitter 100 according to one of the Fig. 1B to Fig. 1F) according to various aspects.

[0042] The method 400 may include (in 402) forming a first mirror structure.

[0043] Method 400 may include (in 404) forming a light-emitting structure over the first mirror structure. The light-emitting structure may be configured to emit light.

[0044] Method 400 may include (at 406) forming a second mirror structure over the light-emitting structure. The first mirror structure and the second mirror structure may be configured to reflect the light emitted by the light-emitting structure.

[0045] Method 400 may include (at 408) forming an epitaxial layer with a grating structure embedded therein. The grating structure may include a plurality of periodically arranged grating elements and may be configured to stabilize the polarization of the emitted light.

[0046] As described above with respect to the surface emitter 100, the epitaxial layer with the grating structure embedded therein can be arranged outside the optical cavity or inside the optical cavity.

[0047] This is how the epitaxial layer can be formed: - between the light-emitting structure and the first mirror structure, or - between the light-emitting structure and the second mirror structure, or - between two of the several layers of the first mirror structure, or - between two of the multiple layers of the second mirror structure, or - between the substrate and the first mirror structure, or - above (e.g. directly on) the second mirror structure.

[0048] Fig. 5 shows schematic cross-sectional views in the manufacturing process of the embedded lattice structure 110 according to various aspects.

[0049] Thus, a first layer may be formed (at 502) as a first portion 114(1) of the epitaxial layer 114 using an epitaxial process. Alternatively, this portion 114(1) may be part of the substrate 108.

[0050] Subsequently (in 504 and 506), the lattice structure 110 can be formed (e.g., directly on) the first part 114(1) of the epitaxial layer 114. For example, as in Fig.5, a layer 510 may be formed (in 504) on the first part 114(1) of the epitaxial layer 114, and subsequently (in 506), for example using photolithography in conjunction with a (wet and / or dry) etching, this layer 510 may be patterned into the grating structure 110. Alternatively, a (e.g., photolithographic) mask having a plurality of openings may be applied first, and the grating structure 110 may be formed by coating the mask and subsequently removing the mask (in the openings).

[0051] Subsequently, a second layer may be formed (at 508) over the first layer and the grating structure 110, as a second portion 114(2) of the epitaxial layer 114, using an epitaxial lateral overgrowth (ELOG) process. It is understood that the first portion 114(1) and the second portion 114(2) of the epitaxial layer 114 may be made of the same materials. In this way, the grating structure 110 may be embedded in the epitaxial layer 114.

[0052] 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.

[0053] Example 1 is a surface emitter comprising: a substrate; a first mirror structure and a second mirror structure arranged above the substrate; a light-emitting structure arranged (vertically) between the first mirror structure and the second mirror structure, wherein the light-emitting structure is configured to emit light, and wherein the first mirror structure and the second mirror structure are configured to reflect the light emitted by the light-emitting structure; and a grating structure comprising a plurality of periodically arranged grating elements embedded in the substrate, wherein the grating structure is configured to polarization stabilize the emitted light.

[0054] Example 2 is configured according to Example 1, wherein the substrate comprises a base substrate and an epitaxial substrate layer, wherein the base substrate and the epitaxial substrate layer are made of the same material, and wherein the plurality of periodically arranged grating elements are embedded between the base substrate and the epitaxial substrate layer.

[0055] Example 3 is configured according to example 1 or 2, wherein a distance between two adjacent grating elements of the plurality of periodically arranged grating elements is in a range of approximately 0.1⋅λ4 to approximately 10·λ, where λ is the wavelength of the emitted light.

[0056] Example 4 is configured according to any one of Examples 1 to 3, wherein a thickness of each grating element of the plurality of periodically arranged grating elements is in a range of about 0.01·λ to about 10·λ, where λ is the wavelength of the emitted light.

[0057] Example 5 is a surface emitter comprising: a first mirror structure and a second mirror structure; a light-emitting structure arranged (vertically) between the first mirror structure and the second mirror structure, wherein the light-emitting structure is configured to emit light, and wherein the first mirror structure and the second mirror structure are configured to reflect the light emitted by the light-emitting structure; an epitaxial layer; and a grating structure comprising a plurality of periodically arranged grating elements embedded in the epitaxial layer, wherein the grating structure is configured to polarization stabilize the emitted light.

[0058] Example 6 is configured according to Example 5, wherein the epitaxial layer is arranged between the light-emitting structure and the first mirror structure; or wherein the epitaxial layer is arranged between the light-emitting structure and the second mirror structure.

[0059] Example 7 is configured according to Example 5, wherein the second mirror structure is arranged over the first mirror structure and wherein the epitaxial layer is arranged over (e.g., directly on) the second mirror structure.

[0060] Example 8 is configured according to Example 5, wherein the first mirror structure comprises a plurality of mirror layers, and wherein the epitaxial layer is arranged between two of the plurality of mirror layers of the first mirror structure; or wherein the second mirror structure comprises a plurality of mirror layers, and wherein the epitaxial layer is arranged between two of the plurality of mirror layers of the second mirror structure.

[0061] Example 9 is configured according to Example 5, wherein the second mirror structure is disposed over the first mirror structure and wherein the epitaxial layer is disposed between a substrate and the first mirror structure.

[0062] Example 10 is configured according to any one of Examples 1 to 9, wherein a distance between two adjacent grating elements of the plurality of periodically arranged grating elements corresponds approximately to an integer multiple of a quarter wavelength of the emitted light.

[0063] Example 11 is configured according to any one of Examples 1 to 10, wherein the epitaxial layer has, at least in a surface region, a defect density (as the number of defects) of less than 1·10 9 cm -2 (e.g. less than 1·10 7 cm -2 , e.g. less than 1·10 5 cm -2 ).

[0064] Example 12 is configured according to any one of Examples 1 to 11, wherein the grating structure comprises (e.g. consists of) a material whose refractive index is at least 0.1 (e.g. at least 0.5, preferably at least 1) greater or smaller than a refractive index of the first mirror structure and / or the second mirror structure.

[0065] Example 13 is configured according to any one of Examples 1 to 12, wherein the lattice structure comprises or consists of a dielectric material (eg, silicon oxide, silicon nitride, aluminum oxide, or titanium oxide), a semimetal, or a semiconductor material.

[0066] Example 14 is configured according to any one of Examples 1 to 13, wherein the first mirror structure and the second mirror structure each comprise a Bragg mirror.

[0067] Example 15 is a method of fabricating a surface emitter, the method comprising: forming a grating structure (directly) on a substrate, wherein the grating structure has a plurality of periodically arranged grating elements; forming an epitaxial layer over the substrate and the grating structure using an epitaxial lateral overgrowth method to embed the plurality of periodically arranged grating elements of the grating structure; and forming a first mirror structure over the epitaxial layer; forming a light-emitting structure over the first mirror structure, wherein the light-emitting structure is configured to emit light; and forming a second mirror structure over the light-emitting structure, wherein the first mirror structure and the second mirror structure are configured to reflect the light emitted by the light-emitting structure.wherein the grating structure is configured to stabilize the polarization of the emitted light;

[0068] Example 16 is configured according to Example 15, wherein the substrate and the epitaxial layer are made of the same material.

[0069] Example 17 is configured according to example 15 or 16, wherein the grating structure is formed such that a distance between two adjacent grating elements of the plurality of periodically arranged grating elements is in a range of approximately 0.1⋅λ4 to approximately 10·λ, where λ is the wavelength of the emitted light.

[0070] Example 18 is configured according to any one of Examples 15 to 17, wherein the grating structure is formed such that a thickness of each grating element of the plurality of periodically arranged grating elements is in a range of about 0.01·λ to about 10·λ, where λ is the wavelength of the emitted light.

[0071] Example 19 is a method of manufacturing a surface emitter, the method comprising: forming a first mirror structure; forming a light-emitting structure over the first mirror structure, wherein the light-emitting structure is configured to emit light; forming a second mirror structure over the light-emitting structure, wherein the first mirror structure and the second mirror structure are configured to reflect the light emitted by the light-emitting structure; and forming an epitaxial layer having a grating structure embedded therein, wherein the grating structure has a plurality of periodically arranged grating elements and is configured to polarization stabilize the emitted light.

[0072] Example 20 is configured according to Example 19, wherein forming the epitaxial layer with the grating structure embedded therein comprises: forming, as a first portion of the epitaxial layer, a first layer using an epitaxial process, forming the grating structure (directly) on the first layer, and forming, as a second portion of the epitaxial layer, a second layer over the first layer and the grating structure using an epitaxial lateral overgrowth process to embed the plurality of periodically arranged grating elements of the grating structure.

[0073] Example 21 is configured according to example 19 or 20, wherein the first layer and the second layer are made of the same material.

[0074] Example 22 is configured according to any one of Examples 19 to 21, wherein the epitaxial layer is formed between the light-emitting structure and the first mirror structure; or wherein the epitaxial layer is formed between the light-emitting structure and the second mirror structure.

[0075] Example 23 is configured according to any one of Examples 19 to 21, wherein the second mirror structure is formed over the first mirror structure and wherein the epitaxial layer is formed over (e.g., directly on) the second mirror structure.

[0076] Example 24 is configured according to any one of Examples 19 to 21, wherein the first mirror structure comprises a plurality of mirror layers, and wherein the epitaxial layer is formed between two of the plurality of mirror layers of the first mirror structure; or wherein the second mirror structure comprises a plurality of mirror layers, and wherein the epitaxial layer is formed between two of the plurality of mirror layers of the second mirror structure.

[0077] Example 25 is configured according to any one of Examples 19 to 21, wherein the second mirror structure is formed over the first mirror structure, and wherein the epitaxial layer is formed between a substrate and the first mirror structure.

[0078] Example 26 is configured according to any one of Examples 15 to 25, wherein the grating structure is formed such that the distance between two adjacent grating elements of the plurality of periodically arranged grating elements corresponds approximately to an integer multiple of a quarter wavelength of the emitted light.

[0079] Example 27 is configured according to any one of Examples 15 to 26, wherein the epitaxial layer has, at least in a surface region, a defect density (as the number of defects) of less than 1 10 9 cm -2 (e.g. less than 1·10 7 cm -2 , e.g. less than 1·10 5 cm -2 ).

[0080] Example 28 is configured according to any one of Examples 15 to 27, wherein the grating structure comprises (eg consists of) a material whose refractive index is at least 0.1 (eg at least 0.5, preferably at least 1) greater or smaller than a refractive index of the first mirror structure and / or the second mirror structure.

[0081] Example 29 is configured according to any one of Examples 15 to 28, wherein the lattice structure comprises or consists of a dielectric material (eg, silicon oxide, silicon nitride, aluminum oxide, or titanium oxide), a semimetal, or a semiconductor material.

[0082] Example 30 is configured according to any one of examples 15 to 29, wherein the first mirror structure and the second mirror structure each comprise a Bragg mirror.

[0083] Example 31 is configured according to any one of Examples 15 to 30, wherein forming the grating structure comprises: forming a layer; and forming the grating structure by patterning the layer into the plurality of periodically arranged grating elements.

[0084] Example 32 is configured according to any one of Examples 15 to 30, wherein forming the lattice structure comprises: forming a mask having a plurality of openings according to the lattice structure; and forming the lattice structure by coating the mask and then removing the mask.

[0085] Example 33 is a control device comprising one or more than one processor configured to perform the method according to any one of Examples 15 to 32.

[0086] Example 34 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 a method according to any of Examples 15 to 32.

[0087] 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).

[0088] 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.

[0089] A structure embedded in another structure (e.g., a layer) can be understood as a structure that is (completely) surrounded on all sides by the other structure (e.g., the layer). Thus, all (outer) surfaces of the structure can be adjacent to the other structure (e.g., be in direct contact with it).

[0090] A structure can be embedded in a layer, for example, using (e.g. by means of) an epitaxial lateral overgrowth (ELOG) process. A first part of the layer can be formed using an epitaxial layer formation process. The structure can then be formed (directly) on the first part of the layer, and subsequently a second part of the layer can be formed on the exposed portions of the first part of the layer and on the structure by means of the epitaxial lateral overgrowth process. In this way, the layer can, for example, be a substantially single-crystalline (epitaxially formed) layer in which the structure is embedded. Epitaxial lateral overgrowth, for example, enables the defect density of the layer to be significantly lower compared to other layer formation processes.One method for epitaxial lateral overgrowth is, for example, hybrid vapor phase epitaxy (HVPE).

[0091] 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 construed as preferred or advantageous over other examples or designs.

[0092] The term "processor," as used herein, can be understood as any type of entity that allows the processing of data or signals. The data or signals can, for example, be processed according to at least one (i.e., one or more than one) specific function performed by the processor. A processor can 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 programmable gate array (FPGA), an integrated circuit, or any combination thereof. Any other type of implementation of the respective functions, which are described in more detail below, can 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 executed (e.g., realized) by a processor through one or more specific functions performed by the processor. The processor may therefore be configured to perform one of the methods described herein or its components for information processing.

[0093] The words “plurality” and “several” in the description or claims expressly refer to a quantity greater than one.

[0094] 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, multiple elements can be connected mechanically, so that they are physically held together (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 communication chain).

[0095] In the above descriptions and the accompanying figures, various components of the surface emitter are depicted as separate elements; however, discrete optical functions can also be implemented as a single element. Accordingly, a single element can also be or become divided into two or more elements.

[0096] 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.

[0097] 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 100 surface emitters 102 light-emitting structure 104 first mirror structure 106 second mirror structure 108 Substrat 110 lattice structure 112 multitude of periodically arranged lattice elements 114 epitaxial layer 114(1) first part of the epitaxial layer 114 114(2) second part of the epitaxial layer 114 300, 400 Method for producing a surface emitter

Claims

[1] Surface emitter (100), comprising: • a substrate (108); • a first mirror structure (104) and a second mirror structure (106) arranged above the substrate (108); • a light-emitting structure (102) arranged between the first mirror structure (104) and the second mirror structure (106), wherein the light-emitting structure (102) is configured to emit light, and wherein the first mirror structure (104) and the second mirror structure (106) are configured to reflect the light emitted by the light-emitting structure (102); and • a grating structure (110) having a plurality of periodically arranged grating elements (112) embedded in the substrate (108), wherein the grating structure (110) is configured to stabilize the polarization of the emitted light. [2] Surface emitter (100) according to claim 1, wherein a distance between two adjacent grating elements (112) of the plurality of periodically arranged grating elements (112) is in a range of approximately 0.1⋅λ4 to approximately 10·λ, where λ is the wavelength of the emitted light; and / or wherein a thickness of each grating element of the plurality of periodically arranged grating elements (112) is in a range from approximately 0.01·λ to approximately 10·λ, where λ is the wavelength of the emitted light. [3] Surface emitter (100), comprising: • a first mirror structure (104) and a second mirror structure (106); • a light-emitting structure (102) arranged between the first mirror structure (104) and the second mirror structure (106), wherein the light-emitting structure (102) is configured to emit light, and wherein the first mirror structure (104) and the second mirror structure (106) are configured to reflect the light emitted by the light-emitting structure (102); • an epitaxial layer (114); and • a grating structure (110) having a plurality of periodically arranged grating elements (112) embedded in the epitaxial layer (114), wherein the grating structure (110) is configured to stabilize the polarization of the emitted light. [4] Surface emitter (100) according to claim 3, wherein the epitaxial layer (114) is arranged between the light-emitting structure (102) and the first mirror structure (104); or wherein the epitaxial layer (114) is arranged between the light-emitting structure (102) and the second mirror structure (106). [5] The surface emitter (100) of claim 3, wherein the second mirror structure (106) is disposed over the first mirror structure (104) and wherein the epitaxial layer (114) is disposed over the second mirror structure (106). [6] Surface emitter (100) according to claim 3, wherein the first mirror structure (104) has a plurality of mirror layers and wherein the epitaxial layer (114) is arranged between two of the plurality of mirror layers of the first mirror structure (104); or wherein the second mirror structure (106) has a plurality of mirror layers and wherein the epitaxial layer (114) is arranged between two of the plurality of mirror layers of the second mirror structure (106). [7] Surface emitter (100) according to claim 3, wherein the second mirror structure (106) is arranged above the first mirror structure (104) and wherein the epitaxial layer (114) is arranged between a substrate (108) and the first mirror structure (104). [8] Surface emitter (100) according to one of claims 1 to 7, wherein a distance between two adjacent grating elements (112) of the plurality of periodically arranged grating elements (112) corresponds to an integer multiple of a quarter wavelength of the emitted light. [9] Surface emitter (100) according to one of claims 1 to 8, wherein the epitaxial layer (114) has a defect density of less than 1 10 9 cm -2 has. [10] Surface emitter (100) according to one of claims 1 to 9, wherein the grating structure (110) comprises a material whose refractive index is at least 0.1 greater or smaller than a refractive index of the first mirror structure (104) and / or the second mirror structure (106). [11] Surface emitter (100) according to one of claims 1 to 10, wherein the grating structure (110) comprises or consists of a dielectric material, a semimetal or a semiconductor material. [12] Surface emitter (100) according to one of claims 1 to 11, wherein the first mirror structure (104) and the second mirror structure (106) each comprise a Bragg mirror. [13] Method (300) for producing a surface emitter (100), the method (300) comprising: • forming (302) a grating structure (110) on a substrate (108), the grating structure (110) comprising a plurality of periodically arranged grating elements (112); • forming (304) an epitaxial layer (114) over the substrate (108) and the grating structure (110) using an epitaxial lateral overgrowth method to embed the plurality of periodically arranged grating elements (112) of the grating structure (110); and • forming (306) a first mirror structure (104) over the epitaxial layer (114); • forming (308) a light-emitting structure (102) over the first mirror structure (104), wherein the light-emitting structure (102) is configured to emit light; and • forming (310) a second mirror structure (106) over the light-emitting structure (102), wherein the first mirror structure (104) and the second mirror structure (106) are configured to reflect the light emitted by the light-emitting structure (102); • wherein the grating structure (110) is configured to stabilize the polarization of the emitted light. [14] The method (300) of claim 13, wherein the substrate (108) and the epitaxial layer (114) are made of the same material. [15] Method (400) for producing a surface emitter (100), the method (400) comprising: • forming (402) a first mirror structure (104); • forming (404) a light-emitting structure (102) over the first mirror structure (104), wherein the light-emitting structure (102) is configured to emit light; • forming (405) a second mirror structure (106) over the light-emitting structure (102), wherein the first mirror structure (104) and the second mirror structure (106) are configured to reflect the light emitted by the light-emitting structure (102); and • Forming (408) an epitaxial layer (114) having a grating structure (110) embedded therein, wherein the grating structure (110) has a plurality of periodically arranged grating elements (112) and is configured to stabilize the polarization of the emitted light.

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