阅读说明：本技术 半导体激光器 (Semiconductor laser device ) 是由 斯文·格哈德 艾尔弗雷德·莱尔 克莱门斯·菲尔海利希 安德烈亚斯·莱夫勒 克里斯托夫·艾克勒 于 2016-09-27 设计创作，主要内容包括：半导体激光器(1)包括半导体层序列(2),所述半导体层序列具有n型传导的n型区域(21)、p型传导的p型区域(23)和位于其之间的用于产生激光辐射的有源区(22)。为了注入电流,直接在p型区域(23)处存在由透明导电氧化物构成的对于激光辐射可穿透的p型接触层(3)。直接在p型接触层(3)处安置有导电的且金属的p型接触结构(4)。p型接触层(3)是外罩层的一部分,使得激光辐射在半导体激光器(1)运行时常规地进入到p型接触层(3)中。半导体层序列(2)的两个棱面(25)形成用于激光辐射的谐振器端面。在直接在棱面(25)中的至少一个棱面处的至少一个电流保护区域(5)中,禁止到p型区域(23)中的电流注入。电流保护区域在垂直于所属的棱面(25)的方向上的扩展为至少0.5μm和最高100μm,并且附加地为用于激光辐射的谐振器长度的最高20％。(The semiconductor laser (1) comprises a semiconductor layer sequence (2) having an n-type region (21) of n-type conductivity, a p-type region (23) of p-type conductivity and an active region (22) located therebetween for generating laser radiation. For injecting the current, a p-type contact layer (3) which is transparent to laser radiation and is composed of a transparent conductive oxide is present directly at the p-type region (23). An electrically conductive and metallic p-contact structure (4) is arranged directly on the p-contact layer (3). The p-type contact layer (3) is part of the outer cladding layer, so that the laser radiation enters the p-type contact layer (3) during operation of the semiconductor laser (1) as usual. The two facets (25) of the semiconductor layer sequence (2) form resonator facets for laser radiation. In at least one current protection region (5) directly at least one of the facets (25), current injection into the p-type region (23) is inhibited. The extent of the current protection region in a direction perpendicular to the associated edge surface (25) is at least 0.5 [ mu ] m and at most 100 [ mu ] m, and additionally at most 20% of the resonator length for the laser radiation.)

1. A semiconductor laser (1) having:

a semiconductor layer sequence (2) comprising an n-type region (21) of n-type conductivity, a p-type region (23) of p-type conductivity and an active region (22) for generating laser radiation located therebetween,

-a p-type contact layer (3) made of a transparent conductive oxide, transparent to the laser radiation, for injecting a current directly into the p-type region (23), and

-a conductive and metallic p-type contact structure (4) directly at the p-type contact layer (3),

wherein

-the p-contact layer (3) is part of an outer cap layer for guiding the laser radiation such that the laser radiation conventionally enters the p-contact layer (3) when the semiconductor laser (1) is in operation,

the semiconductor layer sequence (2) has two facets (25) which form resonator facets for the laser radiation,

-inhibiting current injection into the p-type region (23) in a current protection region (5) directly at least one of the facets (25),

-the extent of the current protection region (5) in a direction perpendicular to the associated facet (25) is at least 0.5 μm and at most 100 μm, and additionally at most 20% of the resonator length for the laser radiation,

-in the current protection region (5), the p-type contact layer (5) is removed and in the current protection region (5) at least one additional layer (63) is applied directly on the p-type region (23),

-said additional layer (63) is electrically insulating, and

-the additional layer (63) is applied not only in the current protection region (5) but also on the associated edge surface (25).

2. Semiconductor laser (1) according to the preceding claim,

wherein the p-type contact layer (3) and the p-type contact structure (4) are butted against another one of the facets (25) in a direction parallel to the active region (22).

3. The semiconductor laser (1) according to claim 1,

wherein in the current protection region (5) the p-contact layer (3) and the p-contact structure (4) are completely removed.

4. The semiconductor laser (1) according to claim 1,

wherein the additional layer (63) has a higher specific thermal conductivity than the p-type region (23).

5. The semiconductor laser (1) according to claim 1,

wherein in the current protection region (5) the p-contact structure (4) completely covers a side face (34) of the p-contact layer (3),

wherein the p-contact layer (3), the p-contact structure (4) and the additional layer (63) follow one another in sequence in a direction parallel to the active region (22) in the current protection region (5).

6. The semiconductor laser (1) according to claim 1,

wherein the additional layer (63) is applied onto the p-type contact layer (3) in the vicinity of the current protection region (5) and is in direct contact with the p-type contact structure (4).

7. The semiconductor laser (1) according to claim 1,

wherein in the current protection region (5) the additional layer (63) is partially or completely covered by the p-type contact structure (4),

wherein the thickness of the additional layer (63) is equal to the thickness of the p-type contact layer (3).

8. The semiconductor laser (1) according to claim 1,

wherein in the current protection region (5), the additional layer (63) is spaced apart from the p-type contact layer (3) in a direction parallel to the active region (22).

9. The semiconductor laser (1) according to claim 1,

wherein the additional layer (63) is designed as an antireflection layer or as a highly reflective layer for the laser radiation generated in the active region (22).

10. The semiconductor laser (1) according to claim 1 or 9,

wherein the thickness of the additional layer (63) at the prism face (25) is equal to the thickness at the p-type region (23) in the extension of the p-type contact layer (3).

11. The semiconductor laser (1) according to claim 1 or 9,

wherein the thickness of the additional layer (63) differs from each other at different legs of the additional layer (63) in the shape of L as seen in cross-section.

12. The semiconductor laser (1) according to claim 1 or 9,

wherein the prism face (25) is only partially covered by the additional layer (63).

13. The semiconductor laser (1) according to claim 1 or 9,

wherein the additional layer (63) partially covers the p-type contact structure (4).

14. The semiconductor laser (1) according to claim 1 or 9,

wherein the additional layer (63) has a higher specific thermal conductivity than the p-type region (23) and than the p-type contact layer (3),

wherein the additional layer (63) comprises one or more of the following materials: al (Al)₂O₃、SiO₂、TiO₂、Ta₂O₅、HfO₂、Si₃N₄AlN, SiC, diamond-like carbon.

15. The semiconductor laser (1) according to claim 1 or 9,

wherein the additional layer (63) has a sequence of layers of alternating high and low refractive indices for the laser radiation.

Technical Field

A semiconductor laser is provided.

The present application claims priority from german patent application 102015116335.7, the disclosure of which is incorporated herein by reference.

Disclosure of Invention

The object to be achieved is: a semiconductor laser having high efficiency and large output power is provided.

The object is also achieved by a semiconductor laser having the features of the independent claim. Preferred developments are the subject matter of the dependent claims.

According to at least one embodiment, the semiconductor laser comprises a semiconductor layer sequence. The semiconductor layer sequence comprises an n-type region of n-type conductivity. Likewise, the semiconductor layer sequence has a p-type region of p-type conductivity. An active region is present between the n-type region and the p-type region. The active region is configured for generating laser radiation based on electroluminescence. In other words, the n-type region, the active region and the p-type region follow one another, preferably directly, along or opposite to the growth direction of the semiconductor layer sequence.

The semiconductor layer sequence is preferably based on a group III-V compound semiconductor material. The semiconductor material is, for example, a nitride compound semiconductor material, such as Al_nIn_1-n-mGa_mN, or a phosphide compound semiconductor material, e.g. Al_nIn_1-n-mGa_mP, or also an arsenide compound semiconductor material, such as Al_nIn_1-n-mGa_mAs, wherein n is 0. ltoreq. n.ltoreq.1, m is 0. ltoreq. m.ltoreq.1, and n + m.ltoreq.1, respectively. The semiconductor layer sequence can have dopants and additional components. For the sake of simplicity, however, only the essential constituents of the crystal lattice of the semiconductor layer sequence, i.e. Al, As, Ga, In, N or P, are described, even if these can be replaced and/or supplemented In part by small amounts of further substances.

According to at least one embodiment, the laser radiation has a wavelength with a maximum intensity which lies in the near ultraviolet spectral range. The near ultraviolet spectral range denotes in particular wavelengths between 200nm and 420nm or between 320nm and 420nm, where limits are included. Alternatively, the semiconductor laser is designed to: visible laser radiation is emitted, for example blue laser radiation or red laser radiation. Blue light preferably relates to a dominant wavelength of at least 420nm and/or at most 490 nm. In particular, red light is understood to mean the dominant wavelength between 600nm and 700nm, including the boundary values. It is also possible to: the laser radiation is near infrared radiation, i.e. radiation having a wavelength with a maximum intensity of, for example, between 700nm and 1600nm, where border values are included. Likewise, laser radiation in the green or yellow spectral range between 490nm and 600nm can be generated.

According to at least one embodiment, a semiconductor laser has a p-type contact layer. The p-type contact layer is preferably directly at the p-type region. Furthermore, a p-type contact layer is provided for injecting current directly into the p-type region.

According to at least one embodiment, the p-type contact layer is made of a material that is transparent to laser radiation. Particularly preferably, the p-type contact layer is made of a material selected from the class of transparent conductive oxides, TCO for short. TCOs, transparent conductive oxides, are transparent, electrically conductive materials, usually metal oxides, i.e. for example zinc oxide, tin oxide, cadmium oxide, titanium oxide, indium oxide or indium tin oxide, ITO for short. In addition to binary metal oxides, e.g. ZnO, SnO₂Or In₂O₃Other than ternary metal oxides, e.g. Zn₂SnO₄、CdSnO₃、ZnSnO₃、MgIn₂O₄、GaInO₃、Zn₂In₂O₅Or In₄Sn₃O₁₂Or mixtures of different transparent conductive oxides, also belong to the TCO group. Furthermore, the TCO does not necessarily have to be of stoichiometric composition and can also be p-doped or n-doped.

According to at least one embodiment, a semiconductor laser includes a p-type contact structure. The p-type contact structure is preferably directly at the p-type contact layer. The p-type contact layer is energized via the p-type contact structure. Thus, the p-type contact structure is conductive.

According to at least one embodiment, the p-type contact structure is formed from a metal or from a metal alloy. The p-type contact structure can be composed of a plurality of sublayers. Preferably, the p-type contact structure comprises or consists of one or more of the following metals, is homogeneously mixed or consists of sublayers: au, Ag, Ni, Sn, Pd, Pt, Rh and Ti.

According to at least one embodiment, the p-type contact layer is part of an outer cap layer of the semiconductor laser. In other words, the p-type contact layer is configured for guiding laser radiation within the semiconductor laser. The outer cover layer represents in particular: the layer has a lower optical refractive index for the laser radiation than a waveguide layer, to which the cladding layer adjoins. In other words, the outer cover layer serves to: the laser radiation is guided in the active region via total reflection. The refractive index of the p-type contact layer is therefore lower than the effective refractive index for the laser radiation in the active region.

According to at least one embodiment, the semiconductor layer sequence has two or more facets. The facets preferably form end faces for a resonator in which the laser radiation is generated and guided. In particular, one of the facets is coated so as to be highly reflective, so that the reflectivity of the facet for the laser radiation is preferably up to 90%, 95%, 99%, or 99.8%. The further facet is preferably designed for coupling out laser radiation from the semiconductor laser, for example, with a relatively low reflectivity of up to 50% or 70% or 85% for the laser radiation. In other words, the two facets form two resonator facets for the laser radiation, between which the resonator extends, wherein the facets are preferably located at mutually opposite ends of the semiconductor layer sequence.

According to at least one embodiment, a semiconductor laser has a current protection region. The current protection region is located directly on at least one of the facets. Preferably, there is a galvanic protection zone at each facet which the laser radiation reaches. In the at least one current protection region, current injection into the p-type region is inhibited. For example, the current injection in the current protection region is reduced by at least a factor of 10 or 100 or 500 compared to the remaining regions of the p-type region. Since the p-type region preferably has only a small electrical conductivity in the direction parallel to the active region, it is possible to prevent the active region from being energized directly at the facet.

According to at least one embodiment, the current protection region has an extension in a direction perpendicular to the associated edge surface of greater than 0, in particular an extension of at least 0.5 μm or 5 μm or 10 μm. Alternatively or additionally, the extension of the current protection region is up to 100 μm or 30 μm or 20 μm. It is also possible to: the extension of the current protection region is up to 20% or 10% or 5% or 2% of the length of the resonator for laser radiation.

In at least one embodiment, the semiconductor laser comprises a semiconductor layer sequence. The semiconductor layer sequence comprises an n-type region of n-type conductivity, a p-type region of p-type conductivity and an active region arranged therebetween for generating laser radiation. For the current injection, a p-type contact layer which is transparent to laser radiation is present directly at the p-type region. A conductive and metallic p-contact structure is arranged directly at the p-contact layer. The p-contact layer is part of an outer cap layer for guiding the laser radiation. The two facets of the semiconductor layer sequence form resonator facets for the laser radiation. In at least one current protection region directly at least one of the two facets, current injection into the p-type region is inhibited. The extent of the current protection region in the direction perpendicular to the associated edge surface is at least 0.5 μm and at most 100 μm and additionally at most 20% of the resonator length for the laser radiation.

In the relatively strongly growing market for laser-based applications, such as for projection, illumination or material processing, the commonly used laser diodes reach limits in terms of their maximum output power, efficiency and lifetime. In the semiconductor laser described here, effective wave guiding can be achieved with small optical losses while the operating voltage is small by means of a transparent p-type contact layer. Similarly, the current protection region reduces the rate of spontaneous failure due to Optical loss at the facet, also referred to as catastropic Optical Damage or simply COD. Furthermore, the p-type region of the semiconductor layer sequence can be formed thinner, since the p-type contact layer is part of the associated cover layer. This can reduce the operating voltage.

According to at least one embodiment, the p-type contact layer and/or the p-type contact structure butt-joint with at least one, or preferably all, of the facets and/or resonator facets in a direction parallel to the active region.

According to at least one embodiment, in operation of the semiconductor laser, the laser radiation conventionally enters the p-type contact layer. In other words, the p-type contact layer is part of a system for guiding waves in a semiconductor laser.

According to at least one embodiment, an electrically insulating layer is present in the at least one current protection region between the p-type contact layer and the p-type region. The insulating layer is electrically insulating or also poorly conductive, so that the electrical conductivity of the insulating layer is then at most 10 times lower than the electrical conductivity of the p-type contact layerOr 100 times or 1000 times. The insulating layer is formed of, for example, a ceramic material, glass, dielectric, nitride, and/or oxide. For example, the insulating layer comprises or consists of one or more of the following materials: al (Al)₂O₃、SiO₂、TiO₂、Ta₂O₅、HfO₂、Si₃N₄AlN, SiC, Diamond-like Carbon, Diamond-L ike-Carbon or D L c for short, the insulating layer is preferably produced by means of atomic layer deposition, a L D for short, it is alternatively possible for the insulating layer to be produced via sputtering, chemical vapor deposition or evaporation.

According to at least one embodiment, the insulating layer has a constant thickness throughout the current protection region. In other words, no targeted thickness variation of the insulating layer is then set.

According to at least one embodiment, the thickness of the insulating layer is at most 75% or 50% or 20% or 5% of the thickness of the p-type contact layer. Alternatively or additionally, the thickness of the insulating layer is at least 20nm or 50nm or 100nm and/or at most 1 μm or 500nm or 100 nm. Alternatively, the insulating layer can be just as thick as the p-type contact layer.

According to at least one embodiment, in the at least one current protection region, the p-type region is modified directly at the p-type contact layer. By means of the modification, the current injection into the p-type region is prevented or strongly reduced in this current protection region. For example, a roughening is produced in the current protection region at the p-type region or the crystal quality of the semiconductor layer sequence and/or the p-type conductivity of the semiconductor layer sequence is reduced. This can be achieved, for example, by sputtering, etching or by plasma damage of the rear side of the semiconductor layer sequence. In other words, the contact resistance between the p-type contact layer and the p-type region is improved by the modification.

According to at least one embodiment, in the at least one current protection region, the p-type contact layer is modified directly at the p-type region. The current injection into the p-type region is reduced in this current protection region by modification of the p-type contact layer. For example, in the case of a transparent conductive oxide for a p-type contact layer, the contact resistance and/or conductivity to the p-type region can be set by appropriate heat treatment in combination with selective covering.

According to at least one embodiment, the p-contact layer and the p-contact structure are removed, preferably completely removed, in the at least one current protection region. In this current protection region, the p-type contact layer and the p-type contact structure are preferably not replaced by other components of the semiconductor laser either. For example, at the current protection region, a recess or cavity is formed at the location of the p-type contact layer and/or the p-type contact structure.

According to at least one embodiment, the p-type contact layer is removed in the current protection region and at least one additional layer is present in the current protection region. The additional layer or layers are electrically insulating and are preferably applied directly at the p-type region. In addition, the at least one additional layer has a specific thermal conductivity greater than the p-type region and/or the p-type contact layer. The additional layer can be formed of the same material as the insulating layer. In this connection, reference is made to the embodiment for the insulating layer with regard to the material for the additional layer.

According to at least one embodiment, in the at least one current protection region, the p-type region has a greater thickness than in the remaining regions of the semiconductor layer sequence. Preferably, no p-type contact layer is present in the current protection region. For example, the p-type region is removed outside the current protection region by etching and is subsequently filled with a p-type contact layer. It is possible here to: the p-type contact layer is flush with the p-type region in a direction away from the active region, at least at the boundary between the current protection region and the remaining region of the semiconductor layer sequence.

According to at least one embodiment, the p-type contact layer is only partially removed in the current protection region. In particular, the refractive index, which changes gradually through the p-type contact layer, is then present in the current protection region. The effective refractive index for the laser radiation in the p-type contact layer in the galvanic protection region preferably decreases here in the direction of the associated prism surface and/or in the direction away from the active region. This reduces optical losses at the edge surface in the current protection region.

According to at least one embodiment, the p-type contact layer is completely removed directly at the associated edge surface. The extent of the region in which the p-type contact layer is completely removed in the direction perpendicular to the prism face is preferably at least 0.5 μm or 2 μm or 5 μm and alternatively or additionally up to 70% or 50% or 20% of the extent of the associated current protection region, also in the case of at least partial removal of the region of the p-type contact layer.

According to at least one embodiment, the p-type contact layer is partially removed in at least one current protection region and the zone from which the p-type contact layer is removed is filled with a protective material that is transparent to laser radiation and electrically insulating or poorly conducting. The difference in conductivity can be expressed as: the conductivity of the protective material is then at most 10 or 100 or 1000 times the conductivity of the p-type contact layer. The protective material can be formed of the same material as the insulating layer. The p-type contact layer as a whole together with the protective material preferably forms a layer with planar parallel limiting surfaces lying opposite one another and with a constant, constant thickness.

According to at least one embodiment, the material of the p-type contact layer and the mixed material are mixed in at least one galvanic protection zone. The hybrid material is electrically insulating and preferably transparent to the laser radiation. The proportion of the mixed material increases here gradually or stepwise towards the relevant edge surface and/or in the direction away from the active region.

According to at least one embodiment, the side faces of the p-type contact layer are completely covered by the protective material, by the material of the insulating layer and/or by the material of the p-type contact structure. The side faces are preferably oriented parallel or approximately parallel to the associated edge faces.

According to at least one embodiment, the p-type contact layer, the p-type contact structure and the additional layer follow one another, in particular directly, in a direction towards the facet and parallel to the active region. Depending on the contact resistance between the p-type region and the p-type contact structure, the current protection region is formed either only by the region having the additional layer or by the region having the additional layer and the p-type contact structure.

According to at least one embodiment, the additional layer is applied not only in the current protection region but also on the associated edge surface. The additional layer can be a stack of layers, via which the reflectivity of the associated edge surface is set. For example, the additional layer is designed as an antireflection layer or as a highly reflective mirror. The additional layer can have a sequence of layers with alternately high and low refractive indices for the laser radiation.

According to at least one embodiment, an additional layer is applied to the p-type contact layer in the vicinity of the at least one current protection region. In this case, the additional layer can be in direct contact with the p-type contact structure. The current protection region is in particular only the region in which the additional layer is in direct contact with the p-type region.

According to at least one embodiment, in the current protection region, the additional layer is partially or completely covered by the p-type contact structure. In particular, the p-type contact structure can then be flush with the associated edge surface.

According to at least one embodiment, the thickness of the additional layer is equal to the thickness of the p-type contact layer. Alternatively, it is possible: the additional layer has a thickness equal to the total thickness of the p-type contact layer and the p-type contact structure. It is furthermore possible that: the thickness of the additional layer is greater than the thickness of the p-type contact layer, but less than the thickness of the p-type contact structure.

According to at least one embodiment, the additional layer is spaced apart from the p-type contact layer and/or the p-type contact structure in a direction parallel to the active region. Thus, in a direction parallel to the active region, a cavity can be formed between the additional layer and the p-type contact layer and/or the p-type contact structure.

Drawings

Hereinafter, the semiconductor laser described herein is explained in detail according to embodiments with reference to the drawings. Like reference numerals are used herein to describe like elements in the various drawings. However, the relationships are not shown to scale, rather individual elements can be exaggerated for better understanding.

The figures show:

fig. 1 to 18 show schematic cross-sectional views of embodiments of the semiconductor laser described herein, and

fig. 19 shows a schematic cross-sectional view of a modification of the semiconductor laser.

Detailed Description

Fig. 1 shows an exemplary embodiment of a semiconductor laser 1. A semiconductor layer sequence 2 is present on the substrate 7. Semiconductor layer sequence 2 has an n-type region 21 of n-type conductivity, an active region 22 and a p-type region 23 of p-type conductivity. The n-type region 21, the active region 22 and the p-type region 23 follow each other directly in a direction away from the substrate 7.

On the one hand, a current is injected into the semiconductor layer sequence 2 from the substrate 7 and/or the n-type region 21 and from the p-type contact layer 3 and the p-type contact structure 4. The P-type contact structure 4 is formed of at least one metal. In particular, the semiconductor laser 1 can be electrically contacted externally via the p-contact structure 4, for example via soldering or via a bonding wire. The p-type contact layer 3 is a transparent conductive layer, In particular made of ITO, In₂O₃、SnO₂Or ZnO, or combinations thereof.

The p-type contact layer 3 is part of the outer cap layer of the semiconductor laser 1. Accordingly, the limited intensity of the laser radiation generated in the active region 22 is conventionally still present in the p-type contact layer 3. For example, the waveguide is substantially confined to the active region 22 and a cladding layer for guiding the wave is formed together with the p-type contact layer 3 by the n-type region 21 on the one hand and by the p-type region 23 on the other hand.

In a direction parallel to the active region 22, the semiconductor layer sequence 2 is bounded by a prism 25. The resulting laser radiation is reflected or coupled out at the facet 25. Correspondingly, a highly reflective or antireflective layer, not shown, is preferably applied to the edge faces 25. In all exemplary embodiments, preferably one passivation layer, not shown in each case, is also present at the semiconductor layer sequence 2.

In the vicinity of the facets 25, in the current protection region 5, an insulating layer 6 is present directly on the p-type region 23 and below the p-type contact layer 3. The injection of current from the p-contact layer 3 directly into the p-region 23 at the facet 25 is inhibited by the insulating layer 6. The current protection region 5 preferably has an extension of 5 μm to 40 μm or 10 μm to 20 μm in the direction away from the prism face 25.

As in all other embodiments too, the p-type region 23 together with the p-type contact layer 3 has a sufficient thickness in order to keep the laser radiation away from the metallic and thus relatively strongly absorbing p-type contact structure 4. In other words, the strength I at the contact structure 4 is negligible, in contrast to the strength in the p-type contact layer 3 itself. For example, the thickness of the p-type contact layer 3, which preferably remains the same, is at least 5nm or 50nm or 100nm and/or at most 1 μm or 0.5 μm or 250nm, for example between 100nm and 250nm, including the boundary values. By using the p-type contact layer 3 as part of the outer cap layer it is possible to: the remaining p-type region 23 is formed relatively thin. Thereby, it is possible to reduce the forward bias of the semiconductor laser 1.

In the remaining embodiments, the variation of the intensity I and the substrate 7, respectively, are not shown. In connection therewith, however, it is preferred that in the remaining embodiments, the same applies as explained in connection with fig. 1, as long as it is not otherwise shown.

In the exemplary embodiment of fig. 2, the current protection region 5 is formed by a local modification 61 of the p-type region 23. For example, the contact resistance between the semiconductor layer sequence 2 and the p-type contact layer 3 is locally increased via sputtering, etching or plasma destruction of the rear side of the p-type region 23, so that no current or substantially no current is injected into the semiconductor layer sequence 2 in the current protection region 5.

In the embodiment of fig. 3, in the current protection region 5, a modified portion 62 is formed in the p-type contact layer 3 itself. For example, in the modified part 62, the p-type contact layer 3 is subjected to a heat treatment, in particular an annealing, so that the contact resistance towards the p-type region increases, or so that the electrical conductivity is reduced in the modified part 62 relative to the remaining region of the p-type contact layer 3.

In the exemplary embodiment of fig. 1 to 3, the p-type contact layer 3 and the p-type contact structure 4 each adjoin a ridge 25 at the semiconductor layer sequence 2. In contrast, in the embodiment of fig. 4, the p-type contact structure 4 and the p-type contact layer 3 are completely removed from the current protection region 5.

In the embodiment of fig. 5, an additional layer 63 is applied in the current protection region 5. The additional layer 63 is preferably made of a material that is transmissive for laser radiation and has a relatively low refractive index. It is also possible to: the additional layer 63 has a refractive index which differs from the refractive index of the contact structure 3 by at most 0.2 or 0.1 or 0.05. By means of the additional layer, it is possible to wave guide the laser radiation in the region of the facets 25.

The additional layer 63 can have a thickness greater than the thickness of the p-type contact layer 3. Alternatively, it is possible: the thickness of the additional layer 63 is equal to or less than the thickness of the p-type contact layer 3. For example, the additional layer 63 is formed of a poorly conductive material, such as Al₂O₃、SiO₂、TiO₂、Ta₂O₅、HfO₂、Si₃N₄Or AlN.

Alternatively, it is possible: the additional layer 63 is formed from an electrically non-conductive, but well thermally conductive material in order to ensure that the region near the prism face 25 is thermally bonded to the well thermally conductive p-type contact structure 4. The material for the additional layer 63 is then in particular diamond-like carbon, SiC or AlN. The specific thermal conductivity of the material used for the additional layer 63 is in this case preferably at least 10W/mK or 50W/mK or 100W/mK.

In a next embodiment, see fig. 6, the p-type region 23 is structured. The thickness of the p-type region 23 is reduced outside the current protection region 5. Therefore, a recess is formed in the p-type region 23 outside the current protection region 5. The depth of the recesses is preferably at least 10nm or 50nm or 100nm and/or at most 1 μm or 0.5 μm or 250 nm. The recess is completely or partially filled by the p-type contact layer 3.

According to fig. 6, the p-type contact layer 3 is flush with the p-type region 23 in the current protection region 5 in a direction away from the active region 22. Alternatively, the p-contact layer 3 can also have a smaller or greater thickness in this recess and thus be exceeded or reversed by the p-region 23.

According to fig. 7, the p-type contact layer 3 extends continuously in the current protection region 5 towards the prism surface 25. This enables a gradual transition of the refractive index of the laser radiation to the prism surface 25, thereby reducing optical loss. The region directly at the facet 25 is preferably completely free of the p-type contact layer 3. In contrast to the illustration, the p-type contact layer 3 can extend not only linearly but also curvedly toward the edge surface 25.

By structuring the interior of the p-type contact layer 3, it is also possible: the refractive index in the current protection region 5 decreases in a direction away from the active region 22. This is possible, for example, by recesses in the p-type contact layer 3, the volume fraction of which increases in the direction away from the active region 22.

In the exemplary embodiment of fig. 8, the region removed from the p-type contact layer 3 is filled with the protective material 64, so that overall again a layer with a layer thickness which remains the same and which reaches the prism surface 25 is obtained. For the protective material 64, the same material can be used as for the insulating layer 6, which in turn can be formed of the same material as the additional layer 63.

In the embodiment of fig. 9, the material of the p-type contact layer 3 is mixed with the hybrid material 65 to form the current protection region 5. In this case, the proportion of the mixture 65 increases monotonically and gradually in the direction of the edge surface 25. For example, the proportion of In, Sn, N, O and/or Zn changes In the direction of the prism face 25, In particular the composition of the ITO can vary.

In the exemplary embodiment of fig. 10, the side 34 of the p-type contact layer 3 is completely covered by the p-type contact structure 4, so that the p-type contact structure 4 is formed in the shape of L when viewed in cross section, for example, when the prism surface 25 is produced or in a further processing step, it is thus possible for the p-type contact structure 4 to protect the p-type contact layer 3 from metal, optionally, an additional layer 63 is also present, which is connected directly to the p-type contact structure 4 in the direction away from the p-type contact layer 3.

In the exemplary embodiment of fig. 11, the additional layer 33 is arranged not only in the extension of the p-type contact layer 3 but also on the prism surface 25, the additional layer 63 is preferably designed as an antireflection layer or as a highly reflective layer for the laser radiation generated in the active region 22, the thickness of the additional layer 63 at the prism surface 25 can be equal to the thickness at the p-type region 23 in the extension of the p-type contact layer 3, likewise the thicknesses at the different legs of the additional layer 63, which is L-shaped when viewed in cross section, can be different from one another, it is likewise possible for the prism surface 25 to be covered only partially by the additional layer 63, unlike in the illustration in fig. 11, and furthermore, the additional layer 63, unlike in the illustration in fig. 11, can partially cover the p-type contact structure 4.

In the embodiment of fig. 12, the additional layer 23 is flush with the p-type contact layer 3 in a direction away from the active region. The p-type contact layer 3 and the p-type contact structure 4 terminate flush with each other in a direction perpendicular to the prism face 25. A corresponding design of the additional layer 63 can also be present in fig. 5, 10 or 11.

According to the exemplary embodiment as shown in fig. 13, the p-type contact layer 3 extends beyond the p-type contact structure 4 in the direction of the prism surface 25. The additional layer 63 here completely covers the p-type contact layer 3 together with the p-type contact structure 4. In the region where the additional layer 63 is applied on the p-type contact layer 3, the additional layer 63 preferably has a smaller thickness than the p-type contact layer 3.

In contrast to fig. 13, the additional layer 63 is formed relatively thick in fig. 14 above the p-type contact layer 3 in the direction away from the active region 22, in particular thicker than the p-type contact layer 3 itself.

In contrast to the illustration in fig. 14, it is also possible in fig. 5 and 10 to 13, respectively: the additional layer 63 does not extend completely to the facet 25. The same applies with respect to fig. 15 to 17.

In the embodiment of fig. 15, the additional layer 63 is partially clad by the p-type contact structure 4, said additional layer completely covering the side 34 of the p-type contact layer 3. In contrast to the illustration, the lateral boundary surface of the p-type contact structure 4 can be formed not only parallel to the edge surface 25, but also obliquely to the edge surface 25 or else rounded.

Unlike fig. 15, the p-type contact structure 4 completely covers the additional layer 63 according to fig. 16.

In the embodiment as shown in fig. 17, an intermediate space, in particular a cavity, is present between the p-type contact layer 3 and the additional layer 63 in a direction parallel to the active region 22. The p-type contact structure 4 and the p-type contact layer 3 extend in a stepped manner in the direction of the prism surface 25.

In fig. 18, the structure of the semiconductor layer sequence 2 is shown in detail. This structure is preferably present in all other embodiments as well. The n-type region 21 is composed of an n-type cladding layer 21a and an n-type waveguide 21b in a direction away from the substrate 7. In the p-type region 23, there are p-type waveguides 23a, 23c, a p-type cladding layer 23d, and a p-type semiconductor contact layer 23e in a direction away from the active region 22. The entire p-type region is preferably based on the same material system. Optionally, the p-type waveguide is divided into two sub-layers 23a, 23c, between which an electron barrier layer 23b can be present.

An additional layer 63, which is electrically insulating or poorly conductive, partially covers the metallic p-contact structure 4 according to fig. 18.

Possible in all embodiments are: the insulating layer 6, the additional layer 63 and/or the protective material 64 consist of a plurality of sublayers, wherein the sublayers preferably directly follow one another in each case. Furthermore, the embodiments can be combined with one another, for example in conjunction with fig. 7, an additional layer 63 can be present in each case, i.e. as shown, for example, in fig. 10 to 17. In all embodiments it is also possible: the prism face 25 is partially or completely covered by an additional layer 63 or also by a protective material 64 and/or an insulating layer 6.

The semiconductor laser 1 has in particular two mutually opposite prism facets 25 oriented parallel to one another. The facets 25 are particularly preferably each provided with a current protection region 5, wherein both facets can be formed by the same type of current protection region 5, or wherein different current protection regions 5, as shown in connection with fig. 1 to 18, can also be combined with one another in a single semiconductor laser 1.

Fig. 19 shows a modification of the semiconductor laser. Here, there is no transparent p-type contact layer, so that the p-type region 23 is relatively thick, which can cause an increase in series resistance and/or forward bias and thus a limited efficiency. In contrast, the semiconductor laser 1 of fig. 1 to 18 has an improved series resistance due to the replacement of the cladding layer by the p-type contact layer 3. Likewise, the stability of the facets 25 is improved because carrier recombination does not take place directly at the facets 25. By eliminating the energization of the facets 25, the occurrence of electrical leakage over the facets 25 is also avoided. Furthermore, the facets 25 are prevented from being contaminated by metal, since all metal can be removed from the facet areas. Furthermore, improved heat dissipation is achieved from the region of the edge surface 25 by means of a highly thermally conductive material, for example by means of the p-type contact structure 4 abutting the edge surface 25.

The invention described herein is not limited to the description according to the embodiment. Rather, the invention encompasses any novel feature and any combination of features, which in particular encompasses any combination of features in the patent claims, even if this feature or this combination itself is not explicitly specified in the patent claims or exemplary embodiments.

According to an embodiment of the present disclosure, the following additional notes are also disclosed:

1. a semiconductor laser (1) having:

a semiconductor layer sequence (2) comprising an n-type region (21) of n-type conductivity, a p-type region (23) of p-type conductivity and an active region (22) for generating laser radiation located therebetween,

-a p-type contact layer (3) made of a transparent conductive oxide, transparent to the laser radiation, for injecting a current directly into the p-type region (23), and

-a conductive and metallic p-type contact structure (4) directly at the p-type contact layer (3),

wherein

-the p-contact layer (3) is part of an outer cap layer for guiding the laser radiation such that the laser radiation conventionally enters the p-contact layer (3) when the semiconductor laser (1) is in operation,

the semiconductor layer sequence (2) has two facets (25) which form resonator facets for the laser radiation,

-in at least one current protection region (5) directly at least one of the facets (25), inhibiting current injection into the p-type region (23), and

-the extent of the current protection region (5) in a direction perpendicular to the associated facet (25) is at least 0.5 μm and at most 100 μm, and additionally at most 20% of the resonator length for the laser radiation.

2. According to the semiconductor laser (1) of the last supplementary note,

wherein the p-type contact layer (3) and the p-type contact structure (4) are in butt joint with at least one of the prism faces (25) in a direction parallel to the active region (22).

3. The semiconductor laser (1) according to any of the above supplementary notes,

wherein in at least one current protection region (5) an electrical insulating layer (6) is present between the p-contact layer (3) and the p-region (23), wherein the insulating layer (6) has a constant thickness of at most 1 μm.

4. The semiconductor laser (1) according to any of the above supplementary notes,

wherein in at least one current protection region (5) the p-type region (23) is modified directly at the p-type contact layer (3) such that in the current protection region (5) current injection into the p-type region (23) is prevented or reduced by a factor of at least 10.

5. The semiconductor laser (1) according to any of the above supplementary notes,

wherein in at least one current protection region (5) the p-contact layer (3) is modified directly at the p-type region (23) such that in the current protection region (5) current injection into the p-type region (23) is prevented or reduced by a factor of at least 10.

6. The semiconductor laser (1) according to any of the above supplementary notes,

wherein in at least one current protection region (5) the p-contact layer (3) and/or the p-contact structure (4) is removed.

7. The semiconductor laser (1) according to any of the above supplementary notes,

wherein in at least one current protection region (5) the p-contact layer (5) is removed and in the current protection region (5) at least one additional layer (63) is applied directly on the p-region (23), wherein the additional layer (63) is electrically insulating.

8. According to the semiconductor laser (1) of the last supplementary note,

wherein the additional layer (63) has a higher specific thermal conductivity than the p-type region (23).

9. The semiconductor laser (1) according to any of the above supplementary notes,

wherein in at least one current protection region (5) the p-type region (23) has a greater thickness than in the remaining zones and the p-type contact layer (3) is removed from the current protection region (5),

wherein the p-type contact layer (3) is in butt joint with the p-type region (23) in the current protection region (5) in a direction away from the active region (22).

10. The semiconductor laser (1) according to any of the above supplementary notes,

wherein in at least one current protection region (5) the p-contact layer (3) is only partially removed, such that in the current protection region (5) the effective refractive index in the p-contact layer (3) for the laser radiation decreases in the direction towards the associated facet (25) and/or in the direction away from the active region (22),

wherein the p-type contact layer (3) is completely removed directly at the associated facet (25).

11. The semiconductor laser (1) according to any of the above supplementary notes,

wherein in at least one current protection region (5) the p-contact layer (3) is partially removed and the following zones are filled with a protective material (64) which is transparent to the laser radiation and electrically insulating: the p-type contact layer (3) is removed from the zone.

12. The semiconductor laser (1) according to any of the above supplementary notes,

wherein in at least one current protection region (5) the material of the p-contact layer (3) is mixed homogeneously with a transparent and electrically insulating mixture material (65),

wherein the proportion of the hybrid material (65) increases gradually or in steps in the direction towards the associated prism face (25) and/or in the direction away from the active region (22).

13. The semiconductor laser (1) according to at least supplementary note 7,

wherein in at least one current protection region (5) the p-type contact layer (3) is completely removed, wherein the p-type contact structure (4) completely covers a side face (34) of the p-type contact layer (3),

wherein the additional layer (63) is additionally applied in the current protection region (5) such that the p-contact layer (3), the p-contact structure (4) and the additional layer (63) follow one another in succession in a direction parallel to the active region (22).

14. The semiconductor laser (1) according to at least supplementary note 7,

wherein, in at least one current protection region (5), the additional layer (63) is applied not only in the current protection region (5) but also on the associated edge surface (25).

15. The semiconductor laser (1) according to at least supplementary note 7,

wherein the additional layer (63) is applied onto the p-contact layer (3) and is in direct contact with the p-contact structure (4) in the vicinity of at least one current protection region (5).

16. The semiconductor laser (1) according to at least supplementary note 7,

wherein in at least one current protection region (5) the additional layer (63) is partially or completely covered by the p-type contact structure (4),

wherein the thickness of the additional layer (63) is equal to the thickness of the p-type contact layer (3).

17. The semiconductor laser (1) according to at least supplementary note 7,

wherein in at least one current protection region (5), the additional layer (63) is spaced apart from the p-type contact layer (3) in a direction parallel to the active region (22).

List of reference numerals

1 semiconductor laser

2 semiconductor layer sequence

21 n type region

22 active region

23 p type region

25 facet

3 transparent p-type contact layer

Side surface of 34 p type contact layer

4-metal p-type contact structure

5 current protection area

6 insulating layer

Modified part of 61 p-type region

Modified part of 62 p type contact layer

63 additional layers

64 protective Material

65 mixing material

Substrate for a semiconductor layer sequence

Intensity of I laser radiation