WO2022243297A1

WO2022243297A1 - Semiconductor laser and optoelectronic semiconductor converter element

Info

Publication number: WO2022243297A1
Application number: PCT/EP2022/063298
Authority: WO
Inventors: Hubert Halbritter; Bruno JENTZSCH; Tilman Ruegheimer; Christoph Walter
Original assignee: Osram Opto Semiconductors Gmbh
Priority date: 2021-05-19
Filing date: 2022-05-17
Publication date: 2022-11-24
Also published as: DE102021113016A1

Abstract

The invention relates to a semiconductor laser (10) comprising a semiconductor layer arrangement (112), having an active zone (115) for radiation generation, as well as comprising a first resonator mirror (125), a second resonator mirror (130) and an optical resonator (105) arranged between the first and the second resonator mirror (125, 130), which optical resonator extends in a direction parallel to a main surface (101) of the semiconductor layer arrangement (112). Lateral boundary surfaces (103) of the semiconductor layer arrangement (112) extend in an oblique manner so that a reflection of generated electromagnetic radiation (15) is produced in the direction of the first main surface (101) of the semiconductor layer arrangement (112). The first and the second resonator mirror (125, 130) are arranged above the first main surface (101) of the semiconductor layer arrangement (112). The semiconductor laser (10) further comprises a converter element (135, 225) above a side of the first resonator mirror (125) facing away from the semiconductor layer arrangement (112).

Description

SEMICONDUCTOR LASER AND OPTOELECTRONIC SEMICONVERTER ELEMENT

DESCRIPTION

Surface emitting semiconductor lasers are widely used as a very high luminance luminous source. In this case, the optical resonator for generating the laser radiation can be aligned parallel or perpendicular to the surface of the semiconductor layer arrangement. In general, concepts are being sought for improving such surface-emitting semiconductor lasers and opening them up for broader areas of application.

The object of the present invention is to provide an improved semiconductor laser and an improved optoelectronic semiconductor converter element.

According to embodiments, the object is solved by the subject matter of the independent patent claims. Advantageous developments are defined in the dependent claims.

A semiconductor laser comprises a semiconductor layer arrangement which has an active zone for generating radiation, a first resonator mirror, a second resonator mirror and an optical resonator which is arranged between the first and the second resonator mirror and extends in a direction parallel to a main surface of the semiconductor layer arrangement. Lateral boundaries of the semiconductor layer arrangement run obliquely, so that electromagnetic radiation generated is reflected in the direction of the first main surface of the semiconductor layer arrangement. The first and the second resonator mirror are arranged above the first main surface of the semiconductor layer arrangement. The semiconductor laser also has a converter element on a side of the first resonator mirror that faces away from the semiconductor layer arrangement. For example, a first and a second lateral boundary surface of the semiconductor layer arrangement can run obliquely. According to embodiments, the semiconductor laser also includes a third mirror, which is designed as a Bragg mirror and is arranged between the first resonator mirror and the converter element. The third mirror is suitable for allowing laser radiation generated by the semiconductor layer arrangement to pass through and for reflecting electromagnetic radiation with a longer wavelength.

A substrate can be arranged between the converter element and the semiconductor layer arrangement. For example, the substrate can be a growth substrate for growing layers of the semiconductor layer arrangement. For example, the layers of the semiconductor layer arrangement can contain GaN. The growth substrate can be a GaN substrate, for example.

According to embodiments, a metallic layer may be arranged over a first main surface of the substrate, wherein the converter element is arranged over a first part of the first main surface and the metallic layer is arranged over a second part of the first main surface of the substrate.

The metallic layer and the first resonator mirror can be directly adjacent to the substrate.

In accordance with further embodiments, the semiconductor laser has a metallic housing which adjoins at least two side faces of the substrate.

The substrate and the first resonator mirror can be doped. The semiconductor laser can also have a first contact element which is electrically connected to a first semiconductor layer of a first conductivity type of the semiconductor layer arrangement and is arranged on a side of the substrate which is remote from the semiconductor layer arrangement. The semiconductor laser can also have a second contact element which is electrically connected to a second semiconductor layer of a second conductivity type of the semiconductor layer arrangement. According to further embodiments, the substrate and the first resonator mirror can be undoped. In this case, for example, a conductive semiconductor layer can additionally be provided on a side of the first resonator mirror that faces the active zone. This conductive semiconductor layer can be suitable for connecting the active zone to a first contact element.

According to embodiments, the semiconductor laser can furthermore have an optical element on a side of the converter element which is remote from the semiconductor layer arrangement.

According to embodiments, the converter element can be integrated into the growth substrate. For example, a first part of the growth substrate can be porous, and quantum dots are introduced into the porous part of the growth substrate. For example, the quantum dots can form the converter element.

For example, a second part of the growth substrate can be removed, so that a first part of the growth substrate, into which the quantum dots are introduced, protrudes in relation to the growth substrate.

According to embodiments, different quantum dots, each causing a conversion to different wavelengths, can be introduced into different porous regions of the growth substrate.

An optoelectronic semiconductor converter element comprises a GaN substrate, a porous GaN layer which is arranged over the GaN substrate, and quantum dots which are embedded in pores of the porous GaN layer.

For example, the porous GaN layer can each have different regions in which different quantum dots are arranged.

A semiconductor laser comprises a semiconductor layer arrangement which has an active zone for generating radiation, a first re resonator mirror, a second resonator mirror and an optical resonator arranged between the first and second resonator mirrors and extending in a direction perpendicular to a main surface of the semiconductor layer arrangement. The semiconductor laser further includes a GaN substrate, a porous GaN layer disposed over the GaN substrate, and quantum dots intercalated in pores of the porous GaN layer, the quantum dots intercalated in the pores of the porous GaN layer represent a converter element.

For example, the semiconductor layer arrangement can contain GaN.

The GaN substrate can represent a growth substrate for growing the semiconductor layer arrangement, for example.

A semiconductor laser arrangement has a plurality of laser elements, each of which has a semiconductor layer arrangement which has an active zone for generating radiation, a first resonator mirror, a second resonator mirror and an optical resonator which is arranged between the first and the second resonator mirror and extends in a direction perpendicular to a main surface the semiconductor layer arrangement extends include. The semiconductor laser array further includes a GaN substrate, a porous GaN layer disposed over the GaN substrate, and quantum dots intercalated in pores of the porous GaN layer, the quantum dots intercalated in the pores of the porous GaN layer represent each converter elements.

For example, different converter elements can be assigned to different laser elements.

For example, the semiconductor layer arrangement can contain GaN.

The accompanying drawings serve to understand examples of execution of the invention. The drawings illustrate exemplary embodiments and, together with the description, serve to explain them. sion. Further exemplary embodiments and numerous of the intended advantages result directly from the following detailed description. The elements and structures shown in the drawings are not necessarily drawn to scale relative to one another. The same reference numbers refer to the same or corresponding elements and structures.

1 shows a cross-sectional view of a semiconductor laser according to embodiments.

2A to 2D show cross-sectional views of the semiconductor laser according to other embodiments.

3A shows a workpiece when manufacturing a semiconductor laser according to embodiments.

3B shows a cross-sectional view of the workpiece according to embodiments.

3C summarizes a method according to embodiments.

4A shows a cross-sectional view of a converter element according to embodiments.

4B shows a cross-sectional view of an optoelectronic semiconductor converter element according to further embodiments.

5A to 5D are cross-sectional views of vertical-cavity semiconductor lasers according to embodiments.

6A to 6J are cross-sectional views of horizontal-cavity semiconductors according to embodiments.

Fig. 6K shows a cross-sectional view of a workpiece when the semiconductor laser is manufactured. In the following detailed description, reference is made to the accompanying drawings which form a part of the disclosure, and in which specific embodiments are shown by way of illustration. In this context, directional terminology such as "top", "bottom", "front", "back", "over", "on", "in front", "behind", "front", "back", etc. is referred to the Alignment related to the figures just described. Because the components of the embodiments can be positioned in different orientations, the directional terminology is used for purposes of explanation and is in no way limiting.

The description of the embodiments is not limiting, as other embodiments exist and structural or logical changes can be made without departing from the scope of the claims. In particular, elements of the exemplary embodiments described below can be combined with elements of other exemplary embodiments described, unless the context dictates otherwise.

The terms "wafer" or "semiconductor substrate" used in the following description may include any semiconductor-based structure that has a semiconductor surface. Wafer and structure are understood to include doped and undoped semiconductors, epitaxial semiconductor layers optionally supported by a base substrate, and other semiconductor structures. For example, a layer of a first semiconductor material may be grown on a growth substrate of a second semiconductor material, such as a GaAs substrate, a GaN substrate, or a Si substrate, or of an insulating material, such as a sapphire substrate.

Depending on the intended use, the semiconductor can be based on a direct or an indirect semiconductor material. Examples of semiconductor materials that are particularly suitable for generating electromagnetic radiation include, in particular, nitride semiconductor compounds, through which, for example, ultraviolet, blue or longer-wave light can be generated, such as GaN, InGaN, AlN, AlGaN, AlGaInN, AlGalnBN, phosphide semiconductor compounds, for example green or longer-wave light can be generated by the example, GaAsP, AlGaInP, GaP, AlGaP , as well as other semiconductor materials such as GaAs, AlGaAs, InGaAs, AlInGaAs, SiC, ZnSe, ZnO, Ga ₂₀₃ , diamond, hexagonal BN and combinations of the materials mentioned. The stoichiometric ratio of the compound semiconductor materials can vary. Other examples of semiconductor materials may include silicon, silicon-germanium, and germanium. In the context of the present description, the term "semiconductor" also includes organic semiconductor materials.

The terms "lateral" and "horizontal" as used in this specification are intended to describe an orientation or alignment that is substantially parallel to a first surface of a substrate or semiconductor body. This can be the surface of a wafer or a chip (die), for example.

The horizontal direction can be, for example, in a plane perpendicular to a growth direction when layers are grown.

The term "vertical" as used in this specification intends to describe an orientation that is substantially perpendicular to the first surface of a substrate or semiconductor body. The vertical direction can correspond to a growth direction when layers are grown, for example.

Usually, the wavelength of electromagnetic radiation emitted from an LED chip can be converted using a converter material containing a phosphor or phosphor. For example, white light can be generated by combining an LED chip that emits blue light with a suitable phosphor. For example, the phosphor may be a yellow phosphor capable of emitting yellow light when excited by the light from the blue LED chip. The phosphor can, for example, absorb part of the electromagnetic radiation emitted by the LED chip. The combination of blue and yellow light is perceived as white light. The color temperature can be changed by adding further phosphors that are suitable for emitting light of a further wavelength, for example a red wavelength. According to further concepts, white light can be generated by a combination containing a blue LED chip and a green and red phosphor. It goes without saying that a converter material can comprise a number of different phosphors, each of which emits different wavelengths.

Examples of phosphors are metal oxides, metal halides, metal sulfides, metal nitrides and others. These compounds can also contain additives that cause specific wavelengths to be emitted. For example, the additives may include rare earth materials. YAG:Ce ³⁺ (yttrium aluminum garnet (YA10 _{I2) activated with cerium)} or (Sr.Bao.Euo. _{!) S} i0 can be used as an example for a yellow phosphor. Further phosphors can be based on MSi0:Eu ²⁺ , where M can be Ca, Sr or Ba. By selecting the cations with an appropriate concentration, a desired conversion wavelength can be selected. Many other examples of suitable phosphors are known.

According to applications, the phosphor material, for example a phosphor powder, can be embedded in a suitable matrix material. For example, the matrix material may comprise a resin or poly mer composition such as a silicone or an epoxy resin. The size of the phosphor particles can be in the micrometer or nanometer range, for example.

According to further embodiments, the matrix material can comprise a glass. For example, the converter material can be formed by sintering the glass, for example SiO with further additives and phosphor powder, with the formation of a phosphor in the glass (PiG). According to further embodiments, the phosphor material itself can be sintered to form a ceramic. For example, as a result of the sintering process, the ceramic phosphor can have a polycrystalline structure.

According to further embodiments, the phosphor material may be grown to form a single crystal phosphor, for example using the Czochralski (Cz) method.

According to further embodiments, the phosphor material itself can be a semiconductor material which has a suitable band gap for absorption of the light emitted by the LED and for emission of the desired conversion wavelength in the volume or in layers. In particular, this can be an epitaxially grown semiconductor material. For example, the epitaxially grown semiconductor material can have a band gap that corresponds to a lower energy than that of the primarily emitted light. Furthermore, several suitable semiconductor layers, each of which emits light of different wavelengths, can be stacked one on top of the other. One or more quantum wells, quantum dots, or quantum wires may be formed in the semiconductor material.

1 shows a cross-sectional view of a semiconductor laser 10 according to embodiments. The semiconductor laser has a semiconductor layer arrangement 112, which contains an active zone 115 for the generation of radiation. For example, the semiconductor layer arrangement can have a first semiconductor layer 110 of a first conductivity type, for example n-type, and a second semiconductor layer 120 of a second conductivity type, for example p-conducting. The active zone 115 is between the first and the second semiconductor layer 110, 120 is arranged. The semiconductor layers, for example the first and/or the second semiconductor layer 110, 120 and semiconductor layers of the active zone 115 can be selected from the GaN material system and can be formed over a GaN substrate 100, for example. For example, an emission wavelength of the semiconductor laser are in a range from 400 to 470 nm.

The active zone can have, for example, a pn junction, a double heterostructure, a single quantum well structure (SQW, single quantum well) or a multiple quantum well structure (MQW, multi quantum well) for generating radiation. The term “quantum well structure” has no meaning here with regard to the dimensionality of the quantization. It thus includes, among other things, quantum wells, quantum wires and quantum dots as well as any combination of these layers.

The semiconductor laser also has a first resonator mirror 125 and a second resonator mirror 130 . An optical resonator 105 is formed in the optical path between the first resonator mirror 125 and the second resonator mirror 130 . As shown in FIG. 1, the semiconductor layer arrangement 112 has an inclined side surface 103, which usually runs at an angle of 45° to a horizontal surface. For example, a dielectric layer can be arranged as a mirror layer 107 on the oblique side face 103 . Because of the difference in refractive index between the side surface 103 of the semiconductor layer arrangement 112 and the adjacent medium, electromagnetic radiation generated in the active zone 115 is reflected upwards through the side surface 103 in each case. The first resonator mirror 125 and the second resonator mirror 130 are each formed as a Bragg mirror and each contain parts of a layer stack made of suitable electrical or semiconductor layers.

In general, the term Bragg mirror includes any arrangement that reflects incident electromagnetic radiation to a large degree (e.g. >90%) and contains a layer stack of thin layers. For example, a Bragg mirror can be formed by a sequence of very thin dielectric or semiconductor layers, each with different refractive indices. For example, the layers can alternately have a high refractive index (n>1.7) and a low refractive index (n<1.7) and be designed as a Bragg reflector. For example, the layer thickness can be l/4, where l indicates the wavelength of the light to be reflected in the respective medium. The layer viewed from the incident light can have a greater layer thickness, for example 3l/4. A Bragg mirror can have, for example, 2 to 50 dielectric or semiconductor layers. A typical layer thickness of the individual layers can be about 30 to 90 nm, for example about 50 nm. The layer stack can also contain one or two or more layers that are thicker than about 180 nm, for example thicker than 200 nm.

For example, the first resonator mirror 125 has a smaller number of layers than the second resonator mirror 130 . The first resonator mirror 125 can have, for example, epitaxially grown semiconductor layers, which contain, for example, AlN/GaN or A-UnN/GaN layer sequences. The second resonator mirror 130 can contain the layers of the first resonator mirror 125 and a second layer sequence 126, which has additionally applied dielectric layers. As a result, the reflectivity of the second resonator mirror 130 is greater than that of the first resonator mirror 125. As a result, the radiation from the second resonator mirror 130 is reflected back into the resonator 105, while part of the generated electromagnetic radiation is transmitted by the first resonator mirror 125 and emitted to the outside.

The semiconductor laser shown in FIG. 1 also has a converter element 135 which is arranged on a side of the first resonator mirror 125 which is remote from the semiconductor layer arrangement 112 . The electromagnetic radiation 15 generated by the active zone 115 is thus guided in the direction of the converter element 135 . The wavelength of the electromagnetic radiation 10 emitted by the semiconductor laser 110 is changed by the converter element 135 .

For example, part of the electromagnetic radiation can be changed to a yellow wavelength, so that by combination with the radiation emitted by the active zone 115, which can be blue for example, white light is generated as a result.

According to embodiments, the semiconductor layers of the first resonator mirror 125 can be doped with dopants of the first conductivity type. In this case, the active zone can be contacted via the first resonator mirror 125 .

As illustrated in FIG. 1 , the semiconductor layer arrangement 112 and the first and at least parts of the second resonator mirror 130 can be arranged over a substrate. For example, the semiconductor layer arrangement 112 and the first and at least parts of the second resonator mirror 130 can be grown as semiconductor layers over a growth substrate 100 . For example, the growth substrate 100 can be a GaN substrate. The further layers of the semiconductor laser 10 can also be based on the GaN material system. The substrate 100 and the first resonator mirror 125 can be doped with dopants of the first conductivity type. A first contact element 140 can be arranged on a side of the substrate 100 which is remote from the semiconductor layer arrangement 112 . A second contact element 145 can be arranged on a second main surface 102 on a side of the semiconductor layer arrangement 112 which is remote from the substrate 100 .

The optical resonator 105 extends in a direction parallel to a main surface of the semiconductor stack 112. For example, a length s of the optical resonator 105 may be in a range of several mm. For example, the resonator length can be more than 1 mm and less than 10 mm. The current path between the first contact element 140 and the second Kontaktele element 145 is indicated in Fig. 1 by dashed lines.

The semiconductor laser 10 can also have a third mirror 136 . For example, the third mirror 136 can be designed as a Bragg mirror and can be arranged between the first resonator mirror 125 and the converter element 135 . The third mirror 136 can be arranged between the substrate 100 and the converter element 135 be. For example, the third mirror 136 can have a layer structure with layers of suitable composition and layer thickness, so that laser radiation generated by the semiconductor layer arrangement 112 is transmitted and electromagnetic radiation with a longer wavelength is reflected. In this way, the laser radiation converted by the converter element 135 can be prevented from returning to the substrate and the optical resonator 105 again.

According to embodiments, a further anti-reflective layer (not shown in FIG. 1 ) can be arranged over the converter element. For example, a lateral extent f of the converter element 135 can be more than 50 gm, for example 100 to 200 gm.

As shown in FIG. 1 , a major part of the main surface 104 of the substrate 100 is covered with a metallic layer 141 . In this way, heat generated in the converter element 135 can be dissipated very well through the metallic layer 141 . Due to the structure shown in FIG. 1, there is good thermal coupling of the semiconductor layer arrangement 112 to the substrate 100. FIG. As a result, high luminance of the semiconductor laser can be achieved. Due to the fact that the converter element 135 is laterally adjacent to the metallic layer 141, generated heat can continue to be dissipated very well. For example, the metallic layer 141 and the first resonator mirror are directly adjacent to the substrate 100 .

According to further embodiments, the heat dissipation can be further improved by a metallic housing. FIG. 2A shows a cross-sectional view of a semiconductor laser 10 according to further embodiments. The cross-sectional view of FIG. 2A is taken in a direction along the y-direction, ie, perpendicular to the direction of the cross-section of FIG. 1. In addition to the elements shown in FIG. 1, that shown in FIG Laser 10 to an additional metallic housing 117 which encloses the substrate 100 along the y and z direction. The metallic housing se 117 can directly adjoin at least two side faces of the substrate 100 . In this way, heat that is generated in the laser 10, for example in the converter element 135, can be better dissipated, thereby increasing the efficiency of the semiconductor laser. For example, further parts of the semiconductor layer arrangement 112 and the contact element 145 can be arranged below parts of the housing 117 . According to further embodiments, however, this part can also be replaced by other components.

The resonator width d of the optical resonator 105 along the y direction can be less than 200 pm, for example. The metal of the metallic housing 117 can be gold, for example, or any other conceivable metal.

FIG. 2B shows a cross-sectional view of a semiconductor laser according to further embodiments, in which the metallic housing 117 extends up to a plane of the second main surface 102 of the semiconductor layer arrangement 112 . In this way, the heat can be dissipated even better. Furthermore, the part of the metallic housing 117 that extends to the second main surface 102 of the semiconductor layer arrangement 112 also represents a first contact element 140. Accordingly, the first and the second contact element of the semiconductor laser of FIG. 2B can each be contacted from one side .

As shown in the examples above, the substrate 100 and the first resonator mirror 125 can each be doped to enable electrical connection via these layers. According to further embodiments, however, the substrate and the first resonator mirror 125 can also be undoped. In this case, an additional doped semiconductor layer 138 of the first conductivity type, for example an n-doped GaN layer, can be provided in order to effect electrical contact.

FIG. 2C shows a schematic cross-sectional view of a semiconductor laser with an additional doped semiconductor layer 138 according to further embodiments. 2C further shows a Current conduction path 139 from the underside of the first contact element 140 in the direction of the doped semiconductor layer 138 and finally into the semiconductor layer arrangement 112. The other components are similar to FIG. 2B.

Due to the special construction of the semiconductor layer arrangement 112 for generating the electromagnetic radiation, only a small light expansion takes place in the embodiments described here. A lateral extent of the converter element 135 can therefore also be comparatively small. As a result, the semiconductor laser 10 can be combined with an optical element 122 according to all embodiments. For example, the optical element 122 can be a collimating lens or another optical element for the parallel direction of the emitted laser radiation 16 . The optical element 122 can be arranged over the converter element 135 . For example, the optical element can be directly adjacent to an upper side of the metallic housing 117 . According to further embodiments, an air gap can also be arranged between the optical element 122 and the metallic housing 117 .

As is further shown in FIG. 2D, a doped semiconductor layer 138 is provided for electrically contacting the semiconductor layer arrangement 112 . It goes without saying that the optical element 132 can also be combined with embodiments in which no doped semiconductor layer 138 for electrical contacting of the semiconductor layer arrangement 112 is provided.

The converter element shown in FIGS. 1 and 2A to 2D can be a ceramic converter element, for example. This can be created, for example, in a separate manufacturing step in the required size and thickness and then attached to the component, for example to the growth substrate 100, using a connecting material that is transparent at least for the wavelength generated by the semiconductor layer arrangement 112. Silicone, transparent glass solder or a dielectric layer, for example, are suitable as transparent connecting material. According to further embodiments, a phosphor can also be deposited areally on the wafer, for example by spraying, screen printing or sedimentation. In this configuration, no connecting material is required. If the phosphor is deposited over an area, the edge quality is important for how the thermal connection between the converter element 135 and the adjoining metal layer, for example the metal housing 117 or the metal layer 141, is implemented.

When selecting the dimension f of the lateral extent of the converter element, it must be taken into account that a large area means that divergent emitted radiation 15 can be used particularly well. However, the disadvantage here is that the lateral thermal connection becomes worse with greater expansion, since the largest heat source is in the center. A typical size of the converter element f corresponds, for example, to the beam divergence (1/e ² ) or the beam expansion up to 5 times the beam expansion (“beam wars”).

In general, the widening of the generated electromagnetic radiation 15 within the GaN substrate (with a refractive index of n<<2.46) is only very small, i.e. it is about a few degrees. Despite a substrate that is thicker than 300 μm, the result is a relatively small laser spot that is very well thermally connected, on the one hand via the substrate 100 and on the other hand via the heat dissipation in the heat sink and via metallic contacts.

To produce the semiconductor laser shown in FIGS. 1 and 2A to 2D, a semiconductor layer stack for forming a first and second resonator mirror 125, 130 and the semiconductor layer arrangement 112 are first epitaxially grown over a growth substrate 100, for example a GaN substrate educated. 3A shows an example of a resulting workpiece 25.

A part of the substrate 100 is then removed, so that part of a surface of the semiconductor layer stack for forming the first and the second resonator mirror 125, 130 is exposed. A further layer sequence 126 for forming the second resonator mirror 130 is then grown over this exposed part. For example, the further layer sequence 126 can have any desired dielectric layers such as SiO, SiN, NbO, TiO,

TaO and others included. The dielectric layers can be applied, for example, by deposition methods such as sputtering and others.

3B shows a cross-sectional view of a resulting workpiece 25.

3C summarizes a method according to embodiments. A method for producing a semiconductor laser includes the formation (S100) of a first resonator mirror and a semiconductor layer arrangement, which has an active zone for generating radiation, over a growth substrate. The method further includes forming a second resonator mirror (S110) such that an optical resonator is formed between the first and second resonator mirrors, which optical resonator extends in a direction parallel to a main surface of the semiconductor layer arrangement. The method further includes defining (S120) lateral boundaries of the semiconductor layer arrangement so that they run obliquely and a reflection of generated electromagnetic radiation takes place in the direction of the first main surface of the semiconductor layer arrangement and the first and the second resonator mirror over the first main surface of the semiconductor layer arrangement are arranged. The method also includes the application (S130) of a converter element over a side of the first resonator mirror that faces away from the semiconductor layer arrangement. Defining (S120) lateral boundaries of the semiconductor layer arrangement can include, for example, an etching process by which sloping side walls are produced, for example at an angle of 45° with respect to a horizontal direction.

As has been described, the semiconductor laser can provide a white luminous source with a very high luminance. The emitted electromagnetic radiation 15 is strongly collimated. 4A shows a cross-sectional view of a semiconductor optoelectronic converter element 20 according to embodiments. The semiconductor converter element 20 comprises a GaN substrate 200 and a porous GaN layer 210 which is arranged over the GaN substrate 200 . In the central region of the porous GaN layer 210, parts of a converter or phosphor material are embedded. In particular, it is envisaged that the particles of the phosphor material are quantum dot particles. More specifically, the phosphor material is in the form of nanoparticles or microcrystals implemented as quantum dots.

Quantum dots ("QDs" or quantum dots, also known as semiconductor nanocrystals) are small crystals of II-VI, III-V, IV-V materials, typically 1 nm to 20 nm in diameter, which ranges in The de Broglie wavelength of the charge carriers lies.The energy difference of the charge carrier states of a quantum dot is a function of both the composition and the physical size of the quantum dots.This means that for a given material, the emission spectrum of the quantum dots can be varied by varying the size Accordingly, a large wavelength range can be generated using quantum dots.

For example, the quantum dots can contain a core material surrounded by a shell material. The band gap of the semiconductor core material can be smaller than the band gap of the semiconductor shell material. For example, the core can be composed of CdSe, and the shell can contain CdS and optionally further layers. According to further embodiments, the core can be constructed from InP, and the shell contains ZnS and, if appropriate, further layers. Powders made from such quantum dot nanoparticles are commercially available. In principle, quantum dots can contain one or more of the following materials: CdS, CdSe, CdTe, CdPo, ZnS, ZnSe, ZnTe, ZnPo, HgS, HgSe, HgTe, MgS, MgSe, MgTe, PbSe, PbS, PbTe, GaN, GaP, GaAs, InP, InAs, CuInS ₂ , CdSi_ _x Se, BaTiQ ₃ , PbZr0 ₃ , PbZr _x Tii_ _x 0 ₃ , Ba _x Sri_ _x , SrTi0 ₃ , LaMnQ ₃ , CaMnQ ₃ and La _3-

_; Approximately _MnO3 The quantum dots embedded in the pores are able to absorb incoming electromagnetic radiation and emit electromagnetic radiation with longer wavelengths. Correspondingly, the region of the porous GaN layer 210 in which the quantum dots are embedded provides a converter element 225 which is suitable for changing the wavelength of incident light.

The porous GaN layer 210 can be produced, for example, by an electrochemical process in which a voltage is applied between a doped GaN layer and a counter-electrode. For example, the pores are formed in an n-doped GaN layer, which is doped with Si, for example. The formation of the nanopores is dependent on a doping level. According to embodiments, the generation of the pores can be accelerated by irradiation with light. According to embodiments, the doped GaN layer for forming the porous GaN layer can be a correspondingly doped part of the growth substrate. According to further embodiments, a Si-doped GaN layer is grown over a GaN substrate. According to embodiments, a transparent intermediate layer can be formed as an etch stop layer 215 between the GaN substrate and the Si-doped GaN layer. The transparent layer or etch stop layer 215 can contain, for example, AlGaN or GaN/InGaN with a Ge doping or undoped GaN.

If a voltage is applied between the n-doped GaN layer and a counter-electrode, the pores only form in the n-doped GaN layer. After formation of the pores, suitable quantum dots can be filled into the pores. This results in an optoelectronic semiconductor converter element which is formed in one piece or integrally with a GaN substrate. As a result, an optoelectronic converter can be provided that is integrally connected to the component and cannot be detached therefrom, thereby improving eye safety, for example. Furthermore, since there is no air environment, the converter element is ideally positioned in the direction of the heat sink. tied. As a result, generated heat can be dissipated very well, thereby improving the efficiency of the device.

According to embodiments, a single quantum dot material can be filled into the created pores, thereby providing a converter element that converts to a wavelength.

As shown in FIG. 4B , according to further embodiments it is also possible to fill different regions of the porous layer 210 with different quantum dot materials, so that different converter element regions 225 ₄ , 225 ₂ , 225 ₃ and 225 ₄ are provided. The different converter element areas 225c, . . . , 225 ₄ can each cause a conversion to different wavelengths.

According to embodiments, a sealing layer 220 may be arranged over the surface of the porous GaN layer. A material of the sealing layer 220 can contain SiO or SiN, for example. A reflection into the substrate can be prevented or suppressed by the sealing layer 220 .

As will be described below, the semiconductor optoelectronic converter element 20 can be combined with a semiconductor laser to provide a high luminance light source for emitting highly collimated radiation. In the case of integration with a GaN-based laser, the growth substrate for forming the semiconductor layer sequence that forms the laser can be used simultaneously for forming the semiconductor converter element 20 .

The optoelectronic semiconductor converter element that has been described with reference to FIGS. 4A and 4B can, for example, be combined with a VCSEL ("Vertical Cavity Surface Emitting Laser").

Fig. 5A shows a cross-sectional view of a semiconductor laser 30, which is a combination of a VCSEL and the described opto- electronic semiconductor converter element 20 includes. The semiconductor laser 30 includes a first resonator mirror 125, a second resonator mirror 130 and an optical resonator 205 which is arranged between the first and the second resonator mirror 125, 130 includes. The layers for forming the optical resonator 205 include a first semiconductor layer 110 of the first conductivity type, e.g. n-type, a second semiconductor layer 120 of the second conductivity type, e.g. p-type, and an active region 115 between the first semiconductor layer 110 and the second semiconductor layer 120 is arranged. The first and second semiconductor layers 110, 120 and the active zone 115 and the layers of the first resonator mirror 125 form the semiconductor layer stack 212. The optical resonator 205 extends perpendicularly to a first main surface 110 of the semiconductor layer arrangement 212. The first resonator mirror 125 can, for example Have AlN / GaN or AlInN / GaN layer sequences that can be grown epitaxially. The second resonator mirror 130 can, for example, comprise dielectric layers, for example SiO, SiN, NbO, TiO, TaO.

The optoelectronic semiconductor converter element is arranged above the semiconductor layer arrangement 212 as described above. More specifically, a GaN substrate 200 and a porous layer 210 are arranged over the semiconductor layer assembly 212 . Quantum dots are filled in a part of the porous GaN layer 210, whereby a converter element 225 is produced. Furthermore, a sealing layer 220 can be arranged over the porous GaN layer 210 .

According to further embodiments, a color filter 218 can additionally be arranged over the sealing layer 220 . However, the color filter 218 can also directly adjoin the porous GaN layer 210 and represent a sealing layer, for example. For example, the color filter layer 218 can be suitable for reflecting blue light back again, so that only converted light is emitted by the semiconductor laser 30 . The use of a Color filters can be beneficial, for example, in cases where pure colors are to be emitted and not a mixture of colors.

FIG. 5B shows a semiconductor laser 30 according to further embodiments. The semiconductor laser 30 contains, for example, two identical semiconductor layer arrangements 212 which are each suitable for emitting laser radiation 15 . The converter element 20 has two different converter element regions 225c, 225 ₂ which are each suitable for emitting laser radiation of different wavelengths. In this way, different wavelengths can be emitted in the different regions of the semiconductor laser. For example, converter element area 225c may be adapted to emit yellow light and converter element area 225 ₂ may be adapted to emit green light. It is also possible for one of the converter elements to emit IR radiation.

As mentioned, the semiconductor layer arrangement 212 of the emission regions can be identical in each case. In accordance with further embodiments, the semiconductor layer arrangement can also be different in each case. According to further embodiments, a color filter can be arranged over the sealing layer 220 . In this way, for example, non-converted light can be reflected back or suppressed. In this way it is possible to provide a semiconductor laser in which a different conversion and thus a different emission wavelength is achieved at the pixel level. FIG. 5B also shows a drive circuit _211c , 2112, which makes it possible to drive individual laser elements in a targeted manner. In this way, certain pixels can be allowed to be selectively switched on and off, thereby enabling a colored display or an image display.

For example, a width f of the converter element 225 or aperture of the semiconductor laser can be a few pm. For example, the width f can be less than 10 pm or else less than 5 pm. The width f can be greater than 500 nm, for example. The layer thickness of the substrate 100 can be in a range from 100 to 300 μm, for example. Since GaN-based VCSELs have a very narrow radiation characteristic, the thin layer thickness causes the Substrate the emitted beam only slightly. As a result, it can be achieved that the emitted radiation 16 of adjacent laser elements or converter element regions 225c, 225 ₂ , . . . 225i does not overlap.

5C shows a cross-sectional view of a semiconductor laser 30 according to further embodiments. In addition to the elements shown in FIG. 5B, the semiconductor laser 30 in FIG. 5C has an array of optical elements 122, for example a microlens array. In this way, for example, emitted light can be better collimated. Of course, optical elements 122, for example a microlens arrangement, can also be combined with other embodiments of the semiconductor laser that are described in the context of this application.

Fig. 5D shows a workpiece 25 in the manufacture of the semiconductor laser which has been described in FIGS. 5A to 5C. For example, a semiconductor layer sequence 212 can be applied over a GaN substrate 200, which has layers for forming the first resonator mirror 125, the first semiconductor layer 110, the active zone 115 and the second semiconductor layer 120. The layers for forming the second resonator mirror 130 can already be applied at this stage of the process. According to further embodiments, the layers for forming the second resonator mirror 130 can also be applied later. A doped layer can then be formed over the second main surface 202 of the GaN substrate. The second main surface 202 is opposite to the first main surface 201 . For example, the n-doped GaN layer may be separated from the GaN substrate by a transparent etch stop layer 215 as previously described. Subsequently, pores can be formed in the layer 210, for example by electrochemical etching, whereby the porous GaN layer 210 arises. Although it is described that an etch stop layer is provided, under certain circumstances the etch stop layer can also be dispensed with. For example, pore growth can be timed to ensure that only a specific surface area is rendered porous. Subsequently, quantum dots can be introduced into regions of the porous GaN layer 120 as previously described. The sealing layer 220 can be applied over the porous GaN layer 210 who the. Furthermore, processing steps can be carried out in order to finish components of the semiconductor laser. For example, the layers of the second resonator mirror 130 can be formed. Electrical contacts can be formed to inject a current into the semiconductor laser.

As has been described, the combination of the opto-electronic semiconductor converter element 20 with a surface-emitting semiconductor laser results in a white light source with high luminance which is suitable for emitting highly collimated laser radiation.

The optoelectronic semiconductor converter element described with reference to FIGS. 4A and 4B can also be combined with the semiconductor laser described in FIGS. 1 and 2A to 2D, the resonator of which runs parallel to a surface of the semiconductor layer arrangement 112.

FIG. 6A shows a corresponding semiconductor laser 10. The individual components shown in FIG. 6A essentially correspond to components shown in FIG. However, in contrast to the embodiments shown in FIG. 1, the converter element 225 is part of the semiconductor substrate 100 or is integrated into the semiconductor substrate 100. Accordingly, there is a converter element 225 at the same height as a first main surface 111 of the semiconductor substrate 100. A sealing layer 220 is arranged over the first main surface 111 of the GaN substrate 100 and encapsulates the region of the substrate 100 in which the quantum dots are introduced. In contrast to the semiconductor laser shown in FIG. 1, no third mirror is arranged between the first resonator mirror 125 and the converter element 225 here. The components of the semiconductor laser 10 in FIG. 6B each correspond to the components of the semiconductor laser in FIG. 2B, so that a detailed discussion is omitted here. Again, the converter element 225 is integrated into the substrate 100 here. A third mirror is not provided.

Components of the semiconductor laser 10 shown in FIG. 6C correspond to the components of the semiconductor laser 10 shown in FIG. 2C, respectively. Contrary to this, the converter element 225 is integrated into the semiconductor substrate 100 here. The third mirror is also missing here. Accordingly, a discussion of the elements is omitted.

The components of the semiconductor laser 10 in FIG. 6D each correspond to the components of the semiconductor laser 10 in FIG. 2D. Deviating from the illustration in FIG. 2D, the converter element 225 is integrated into the semiconductor substrate here. Furthermore, the third mirror is missing. The optical element 122 is applied flush to the metal housing 117 . In this way, a semiconductor laser can be integrated with optical elements 122 in a more compact manner.

According to further embodiments, after the converter elements 225 have been formed, part of the first main surface of the growth substrate 100 can be etched back, resulting in recessed regions 113 of the first main surface. This is illustrated in Figure 6E. Here, a part of the surface of the substrate 100 in which no converter element 225 is formed is etched back. As a result, the converter element 225 protrudes from the substrate 100 . Nevertheless, the converter element 225 is formed in one piece with the substrate 100 . In this case, for example, the metallic housing 117 can be formed in such a way that it encloses the converter element 225 laterally. In this way, a particularly good thermal contact with the converter element 225 can be provided and, furthermore, the semiconductor laser 10 can be made more compact.

FIG. 6F shows a semiconductor laser 10 according to further embodiments. Here the substrate 100 has recessed areas 113 . In addition, diffusers 222, for example made of Ti0 ₂ , are arranged adjacent to the converter element 225. The diffusers scatter light back efficiently and thus form a quasi-aperture. In this case, the diffusers 222 efficiently scatter the light back over a wide band, ie in particular the white portion.

According to further embodiments, for example based on the structure shown in FIG. 6E , part of the metallic housing 117 above the recessed area 113 can be made thinner so that the converter element 225 protrudes above the housing 117 . In this case, for example, the anti-reflective layer 220 can be arranged opposite all side surfaces of the converter element 225 in order to reduce a reflection of the electromagnetic radiation back in the direction of the active zone.

This is illustrated in Figure 6G.

As shown in FIG. 6H, the converter element 225 can also be formed like a lens. In this way, any radiation characteristic can be achieved.

FIG. 61 shows a further configuration of the semiconductor laser 10. For example, as illustrated in FIG. Furthermore, both the first and the second resonator mirror 125, 130 can be constructed from a single semiconductor layer stack, for example AlN/GaN or AlInN/GaN layers. As a result, in this case, the first and second resonator mirrors have an identical reflectivity. Correspondingly, electromagnetic radiation can be emitted from both sides of the active zone and then converted by the converter element 225 . As a result, a semiconductor laser with a larger emission area can be provided. Other elements of the semiconductor laser shown in FIG. 6I have been described with reference to FIGS. 6A and 1. FIG. According to further embodiments, it is possible to provide different converter elements 225c, 225 ₂ in each case with such an embodiment of the first and second resonator mirrors 125 , 130 . Accordingly, electromagnetic radiation of different wavelengths can be emitted on both sides of the active zone 115 . Other elements of the semiconductor laser shown in FIG. 6I have been described with reference to FIGS. 6A and 1. FIG.

According to further embodiments, it is possible to provide a color filter 218 above the converter element 225 in each case. In this way, residual blue light can be suppressed or reflected back.

FIG. 6K illustrates a semiconductor stack or workpiece 25 for fabricating the semiconductor laser described with reference to FIGS. 6A through 6J. About a GaN substrate 200 layers for forming the first resonator mirror 125, the first semiconductor layer 110, the active region 115 and the second semiconductor layer 120 are formed. Subsequently, the porous GaN layer 210 is formed in the manner as described above. Optionally, a transparent etch stop layer can be provided. According to further embodiments, however, this layer can also be dispensed with. The etch stop layer can be, for example, AlGaN or GaN(InGaN) with a Ge doping or undoped GaN. The doping level of the porous layer 210 can be greater than 5*10 ¹⁸ /cm ³ , for example. By introducing quantum dots into the porous layer 210, the converter element 225 (not shown in FIG. 6K) can be fabricated as previously described. Further steps for producing elements of the semiconductor laser can then be carried out.

The semiconductor lasers described here can be used, for example, as a light source, for example as a white light light source, or as a broadband light source with high luminance. Furthermore, in particular the semiconductor laser arrays described can be used as display devices, for example as an RGB display device. Although specific embodiments have been illustrated and described herein, those skilled in the art will recognize that a variety of alternative and/or equivalent configurations may be substituted for the specific embodiments shown and described without departing from the scope of the invention. The application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, the invention is to be limited only by the claims and their equivalents.

REFERENCE LIST

10 semiconductor lasers

15 generated electromagnetic radiation

16 converted electromagnetic radiation

20 semiconductor converter element

25 workpiece

30 semiconductor lasers

100 substrate

101 first main surface of the semiconductor layer arrangement

102 second main surface of the semiconductor layer arrangement

103 lateral boundary surface

104 first major surface of the substrate

105 cavity

107 mirror layer

108 first part of the first main surface

109 second part of the first main surface

110 first semiconductor layer

111 first major surface of the substrate

112 semiconductor layer arrangement

113 recessed areas of the first major surface

115 active zone

117 metallic case

120 second semiconductor layer

122 optical element

125 first resonator mirror

126 second layer sequence

130 second resonator mirror

135 converter element

136 third mirror

138 doped semiconductor layer

139 power line path

140 first contact element

141 metallic layer

145 second contact element

200 GaN substrate

201 first main surface of the GaN substrate 202 second main surface of the GaN substrate

205 optical resonator

210 porous GaN layer

211c, 211 ₂ driving circuit

212 semiconductor layer arrangement

215 etch stop layer

218 color filters

220 sealing layer

222 TiO diffuser

225 converter element

225c, 225 ₂ converter element area

Claims

EXPECTATIONS

1. Semiconductor laser (10) with a semiconductor layer arrangement (112), which has an active zone (115) for generating radiation, a first resonator mirror (125), a second resonator mirror (130) and a resonator mirror (125 , 130) arranged optical resonator (105), which extends in a direction parallel to a main surface (101) of the semiconductor layer arrangement (112), lateral boundary surfaces (103) of the semiconductor layer arrangement (112) running obliquely, so that a reflection of generated electromagnetic radiation (15) takes place in the direction of the first main surface (101) of the semiconductor layer arrangement (112) and the first and the second resonator mirror (125, 130) are arranged over the first main surface (101) of the semiconductor layer arrangement (112), and the semiconductor laser ( 10) also a converter element (135, 225) on a layer arrangement (112) facing away from the semiconductor side of the first resonator has mirrors (125).

2. Semiconductor laser (10) according to claim 1, further having a third mirror (136), which is designed as a Bragg mirror and between the first resonator mirror (125) and the converter element (135,

225) is arranged and which is suitable for the semiconductor layer arrangement (112) to transmit laser radiation (15) generated and to reflect electromagnetic radiation (16) with longer wavelengths.

3. Semiconductor laser (10) according to claim 1 or 2, further comprising a substrate (100) between the converter element (135, 225) and the semiconductor layer arrangement (112).

4. Semiconductor laser (10) according to claim 3, further comprising a me-metallic layer (141) over a first main surface (104) of the substrate (100), wherein the converter element (135) over a first Part of the first main surface (104) and the metallic layer (141) is arranged over a second part of the first main surface (104) of the substrate (100).

5. Semiconductor laser (10) according to claim 4, wherein the metallic layer (141) and the first resonator mirror (125) directly adjoin the substrate (100).

6. The semiconductor laser (10) according to claim 3 or 4, further comprising a metal housing (117) adjoining at least two side faces of the substrate (100).

7. Semiconductor laser (10) according to any preceding Ansprü surface, wherein the substrate (100) and the first resonator mirror (125) are doped.

The semiconductor laser (10) of any one of claims 1 to 7, wherein the substrate (100) and the first resonator mirror (125) are undoped, further comprising a conductive semiconductor layer (138) on a side of the first one facing the active region (115). Resonator mirror (125) which is suitable for connecting the active zone (115) to a first contact element (140).

9. Semiconductor laser (10) according to any one of the preceding claims, further comprising an optical element (122) on one of the semiconductor layer arrangement (112) facing away from the converter element (135, 225).

10. Semiconductor laser (10) according to any one of claims 3 to 9, wherein the substrate (100) is a growth substrate for the semiconductor layer arrangement (112).

11. Semiconductor laser (10) according to claim 9 or 10, wherein the converter element (135, 225) is integrated into the growth substrate (200).

12. The semiconductor laser (10) according to claim 11, wherein a first part (210) of the growth substrate (200) is porous and quantum dots are introduced into the porous part (210) of the growth substrate.

13. The semiconductor laser (10) according to claim 12, wherein a second part of the growth substrate (200) is removed so that a first part of the growth substrate (200) into which the quantum dots are introduced protrudes from the growth substrate (200).

14. Semiconductor laser (10) according to claim 12 or 13, wherein ver different quantum dots, each causing a conversion to different wavelengths Chen, are introduced into different porous areas of the growth substrate (200).

15. Semiconductor laser (10) according to any one of the preceding claims, wherein the semiconductor layer arrangement (112) contains GaN.

16. A semiconductor optoelectronic converter element (20), comprising: a GaN substrate (200); a porous GaN layer (210) arranged over the GaN substrate (200),

Quantum dots stored in pores of the porous GaN layer (210).

17. Optoelectronic semiconductor converter element (20) according to claim 16, wherein the porous GaN layer (210) has different Liche areas in each of which different quantum dots are arranged.

18. Semiconductor laser (30) with: a semiconductor layer arrangement (112) having an active zone (115) for generating radiation, a first resonator mirror (125), a second resonator mirror (130) and a resonator mirror between the first and the second resonator mirror ( 125, 130) arranged optical resonator (105), extending in a direction perpendicular to a main surface (101) of the semiconductor stack (112), a GaN substrate (200); a porous GaN layer (210) disposed over the GaN substrate (200), and

Quantum dots, which are stored in pores of the porous GaN layer (210), the quantum dots stored in the pores of the porous GaN layer representing a converter element (20).

19. Semiconductor laser (30) according to claim 18, wherein the semiconductor layer arrangement (112) contains GaN.

20. Semiconductor laser arrangement (30) with a plurality of laser elements, each of which has: a semiconductor layer arrangement (112) which has an active zone (115) for generating radiation, a first resonator mirror (125), a second resonator mirror (130) and one between the first and the second resonator mirror (125, 130) arranged optical resonator (105) extending in a direction perpendicular to a main surface (101) of the semiconductor layer assembly (112), further comprising a GaN substrate (200); a porous GaN layer (210) disposed over the GaN substrate (200), and

Quantum dots which are embedded in pores of the porous GaN layer, the quantum dots embedded in the pores of the porous GaN layer each representing converter elements.

21. The semiconductor laser arrangement (30) as claimed in claim 20, in which different converter element regions (225c, 2252 ₎ are assigned to different laser elements in each case.