Semiconductor Laser and Method of Producing a Semiconductor Laser

Abstract

In an embodiment a semiconductor laser includes a semiconductor body having a plurality of resonator regions, wherein the resonator regions are arranged side by side along a lateral direction, each resonator region having an active region configured to generate radiation, wherein the semiconductor body extends between two side faces, wherein the resonator regions are configured to emit laser radiation at one of the two side faces, and a layer sequence attached to at least one of the side faces, wherein the layer sequence forms at least part of a resonator mirror for at least one resonator region.

Claims

1-19. (canceled)

20. A semiconductor laser comprising: a semiconductor body having a plurality of resonator regions, wherein the resonator regions are arranged side by side along a lateral direction, each resonator region having an active region configured to generate radiation, wherein the semiconductor body extends between two side faces, wherein the resonator regions are configured to emit laser radiation at one of the two side faces; and a layer sequence attached to at least one of the side faces, wherein the layer sequence forms at least part of a resonator mirror for at least one resonator region.

21. The semiconductor laser according to claim 20, wherein the layer sequence comprises a plurality of subregions, which are different from one another, and wherein a subregion in each case forms, for one of the resonator regions, at least part of the resonator mirror associated with the at least one resonator region.

22. The semiconductor laser according to claim 21, wherein resonator mirrors formed by the subregions differ from each other with respect to their wavelength of maximum reflectivity.

23. The semiconductor laser according to claim 20, wherein the wavelengths of maximum emission of at least two of the radiations emittable from the resonator regions differ from each other by at least 3 nm and by at most 20 nm.

24. The semiconductor laser according to claim 20, wherein the layer sequence is attached by a direct bond connection to a connection surface on the side face of the semiconductor body.

25. The semiconductor laser according to claim 24, wherein the connection surface is one of the side faces of the semiconductor laser.

26. The semiconductor laser according to claim 25, wherein the connection surface is formed by a coating applied to one of the side faces of the semiconductor laser.

27. The semiconductor laser according to claim 20, wherein the layer sequence is attached to one of the side faces of the semiconductor body by an adhesive layer.

28. The semiconductor laser according to claim 27, wherein the adhesive layer is applied to a coating of a side face of the semiconductor laser.

29. The semiconductor laser according to claim 28, wherein the coating is applied to an output side of the semiconductor body and has a reflectivity of at most 1%.

30. The semiconductor laser according to claim 27, wherein an optical layer thickness of the adhesive layer is smaller than a quarter of the smallest wavelength of maximum emission of the radiation emittable from the resonator regions in a material of the adhesive layer.

31. The semiconductor laser according to claim 20, wherein the layer sequence is attached to one of the side faces of the semiconductor body via a spacer.

32. The semiconductor laser according to claim 20, wherein the layer sequence is arranged on a substrate body.

33. The semiconductor laser according to claim 32, wherein the substrate body comprises a reflection reducing coating on a radiation exit surface.

34. The semiconductor laser according to claim 32, wherein the substrate body has a deflection surface configured to deflect the radiation emerging from one of the side faces of the semiconductor laser.

35. A method for producing a semiconductor laser, the method comprising: providing a semiconductor body having a plurality of resonator regions, the resonator regions being arranged side by side along a lateral direction and each resonator region having an active region for generating radiation; forming a dielectric layer sequence on a substrate body; and attaching the dielectric layer sequence to a side face of the semiconductor body, wherein the dielectric layer sequence for at least one resonator region forms at least part of a resonator mirror.

36. The method according to claim 35, wherein the layer sequence is attached to the side face by a direct bond connection.

37. The method according to claim 35, further comprising removing the substrate body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] FIGS. 1A to 1C show an exemplary embodiment of a semiconductor laser, where FIG. 4A is a schematic sectional view and FIG. 1B is a schematic top view. FIG. 1C schematically shows an example of a spectral curve of the reflectivity product R formed by the product of the reflectivities of the resonator mirrors;

[0047] FIGS. 2A and 2B show an exemplary embodiment of a semiconductor laser in schematic sectional view (FIG. 2A) and in plan view (FIG. 2B);

[0048] FIGS. 3A and 3B show an exemplary embodiment of a semiconductor laser in schematic sectional view (FIG. 3A) and in plan view (FIG. 3B);

[0049] FIG. 4 shows an exemplary embodiment of a semiconductor laser in schematic sectional view;

[0050] FIG. 5 shows an exemplary embodiment of a semiconductor laser in schematic sectional view;

[0051] FIG. 6 shows an exemplary embodiment of a semiconductor laser in schematic sectional view;

[0052] FIG. 7 shows an exemplary embodiment of a semiconductor laser in schematic sectional view;

[0053] FIG. 8 an exemplary embodiment of a semiconductor laser in schematic sectional view; and

[0054] FIGS. 9A to 9C show an exemplary embodiment of a method of producing a semiconductor laser by means of intermediate steps shown in schematic plan view in FIGS. 9A and 9C and in a sectional view through the substrate body in FIG. 9B.

[0055] Identical, similar or similarly acting elements are given the same reference signs in the figures.

[0056] The figures are each schematic representations and therefore not necessarily to scale. Rather, individual elements and in particular layer thicknesses may be shown exaggeratedly large for improved representation and/or better understanding.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0057] In the embodiments shown in FIGS. 1A and 1B, the semiconductor laser 1 has a semiconductor body 2 with a plurality of resonator regions 3. In the exemplary embodiment shown, the semiconductor laser 1 has four resonator regions 3. However, the number of resonator regions may vary within wide limits. For example, the number of resonator regions 3 ranges from 2 inclusive to 20 inclusive.

[0058] The resonator regions 3 are arranged adjacent to each other along a lateral direction, and each has an active region 20 provided for generating radiation. The active region 20 is arranged between a first semiconductor layer 21 of a first conductivity type and a second semiconductor layer 22 of a second conductivity type different from the first conductivity type, so that the active region 20 is in a pn junction. For example, the first semiconductor layer 21 is n-type and the second semiconductor layer 22 is p-type. The first semiconductor layer 21, the second semiconductor layer 22, and the active region 20 are typically each formed in multiple layers. For example, the active region 20 has a quantum structure with one or more quantum wells.

[0059] This is not explicitly shown for simplified illustration. Furthermore, electrical contact surfaces or contact layers for electrical contacting of the semiconductor laser 1 are also not shown.

[0060] The semiconductor body 2 is arranged on a carrier 29, for example a growth substrate for the epitaxial deposition of the semiconductor layers of the semiconductor body 2. However, the carrier 29 may also be different from the growth substrate and may be attached to the semiconductor body 2 by wafer bonding, for example, during the production of the semiconductor laser 1.

[0061] The semiconductor body 2 extends between two opposite side faces 25, which delimit the semiconductor body 2 in the lateral direction. During operation of the semiconductor laser 1, laser radiation emerges from the resonator regions 3 at one of the two side faces 25. This is illustrated by arrows 9 in FIGS. 1A and 1B, respectively.

[0062] A layer sequence 4 is attached to one of the side faces 25, in the embodiment shown, the side face 25 where the laser radiation exits the semiconductor laser 1. The layer sequence 4 has a plurality of subregions 40. The subregions 40 are different from each other, wherein one subregion 40 is provided for each of the resonator regions 3 and forms the resonator mirror 5 for the respective resonator region 3.

[0063] On the opposite side face 25, the resonator mirror 5 is formed by a highly reflective coating 75. For example, the highly reflective coating has a reflectivity of at least 95%, for example 99% or more, for the laser radiation to be generated by the semiconductor laser.

[0064] The layer sequence 4 is formed, for example, by a sequence of several layers, for example oxide layers and/or nitride layers, with adjacent layers each having different refractive indices from one another, so that a Bragg mirror is formed. The subregions 40 of the layer sequence differ from each other with respect to their wavelength of maximum reflectivity. This is shown schematically in FIG. 1C. Here, the spectral variation of the reflectivity product R from the reflectivity of the two resonator mirrors 5 is shown schematically for each of the four subregions 40. The spectral difference of this reflectivity product R results in particular from the different design of the subregions 40. For this purpose, the subregions 40 can differ from each other with respect to the layer thicknesses, the materials and/or the number of layers.

[0065] The highly reflective coating 75 forming the opposite resonator mirror 5 can be the same for all resonator regions 3. By means of the subregions 40 differing from each other with respect to their wavelength of maximum reflectivity 1, 2, 3, 4, it can be achieved that the resonator regions 3 have different wavelengths of maximum emission from each other. For example, the difference for at least two of the resonator regions 3 is between 3 nm and 20 nm inclusive. These different wavelengths of maximum reflectivity cause corresponding different wavelengths of maximum emission of the semiconductor laser 1. As schematically shown in FIG. 1C, the wavelengths of maximum reflectivity and thus the wavelengths of maximum emission for all semiconductor lasers may differ from each other in pairs.

[0066] The subregions 40 of the layer sequence 4 can alternatively or additionally be formed in such a way that the radiation emitted by the associated resonator regions 3 differs in polarization for at least two resonator regions. For example, the polarizations of the radiation emitted by adjacent resonator regions 3 can be oriented perpendicular to each other. This can further reduce artifacts caused by closely spaced emission regions.

[0067] In the exemplary embodiment shown in FIGS. 1A and 1B, the layer sequence 4 is attached to the side face of the semiconductor body 2 by a direct bond connection to a connection surface 6. Here, the connection surface 6 is the side face 25 of the semiconductor body. Thus, the layer sequence 4 is directly adjacent to the side face 25 of the semiconductor body 2. Thus, although the active regions 20 of the resonator regions 3 are at least nominally not different from each other, the individual resonator regions 3 each emit radiation at different wavelengths of maximum emission from each other. Resonator regions 3 with different wavelengths of maximum emission can therefore be integrated in a common semiconductor body 2. Thus, small distances between the resonator regions 3 can be achieved, especially compared to individual semiconductor chips placed side by side.

[0068] In the exemplary embodiment shown in FIGS. 1A and 1B, the layer sequence 4 is arranged on a substrate body 45. The substrate body 45 forms a radiation exit surface 46 of the semiconductor laser. The substrate body 45 is expediently transmissive to the radiation generated by the semiconductor laser 1. However, the substrate body 45 may also be opaque to the radiation generated by the semiconductor laser 1 if the layer sequence 4 does not form the resonator mirror 5 at which the radiation is emitted during operation of the semiconductor laser, but forms the opposite resonator mirror 5.

[0069] The semiconductor body 2 comprises, for example, a III-V compound semiconductor material. The radiation to be generated is, for example, in the ultraviolet, visible or infrared spectral range.

[0070] For the formation of the resonator regions 3, for example, a structuring of the semiconductor bodies into ridge waveguides or a planar design of the semiconductor laser 1 is suitable, in which the radiation propagating in the resonator region 3 is gain-guided in the lateral direction.

[0071] The exemplary embodiment shown in FIGS. 2A and 2B is substantially the same as the exemplary embodiment described in connection with FIGS. 1A and 1B. In contrast, the connection surface 6 is formed by a coating 7 of a side face 25 of the semiconductor laser 1. The coating 7 may form resonator mirrors 5 for the resonator regions 3 together with the layer sequence 4, respectively. The coating 7 extends continuously over adjacent resonator regions 3, in particular over all resonator regions 3 of one semiconductor laser 1. Thus, no lateral structuring of the coating 7 is required when creating the coating 7. Suitable materials for the coating 7 are, for example, those indicated in connection with the layer sequence 4, for example a dielectric material, such as an oxide. The direct bond connection at the connection surface 6 can be made between two layers of the same material type, for example between two oxide layers. A direct bond connection can thus be formed particularly reliably.

[0072] The exemplary embodiment illustrated in FIGS. 3A and 3B is substantially the same as the exemplary embodiment described in connection with FIGS. 1A and 1B. In contrast, the substrate body 45 has a deflection surface 48. At the deflection surface 48, radiation emerging from the semiconductor body 2 and coupled into the substrate body 45 is deflected so that a main radiation direction of the semiconductor laser is arranged at an angle to the main extension plane of the active region 20. In the exemplary embodiment shown in FIGS. 3A and 3B, the angle is 90 so that the semiconductor laser radiates perpendicularly to the main extension plane of the active region 20. Thus, the radiation exit surface 46 is parallel to the main extension plane of the active region 20 of the semiconductor 1. However, other radiation angles can be set.

[0073] In the exemplary embodiment shown in FIG. 3A, the reflection at the deflection surface 48 takes place by total reflection at the deflection surface 48. Deviating from this, however, a reflective layer, for example a metal layer or a Bragg mirror, can also be arranged at the deflection surface 48.

[0074] Such a deflection surface may also be applied in the exemplary embodiments according to FIGS. 2A and 2B, 4, 5, 6 and 7.

[0075] The exemplary embodiment shown in FIG. 4 is essentially the same as the exemplary embodiment described in connection with FIGS. 1A and 1B. In contrast, the radiation exit surface 46 of the substrate body 45 has a reflection reducing coating 47. By means of the reflection reducing coating, the radiation portion that could be reflected at the radiation exit surface 46 and thus coupled back into the semiconductor body 2 can be minimized.

[0076] Such a reflection reducing coating 47 may also be applied to the other exemplary embodiments having a substrate body 45.

[0077] The exemplary embodiment shown in FIG. 5 is substantially the same as the exemplary embodiment shown in connection with FIGS. 1A and 1B.

[0078] In contrast, the layer sequence 4 is attached to a side face 25 of the semiconductor body 2 by means of an adhesive layer 65. A layer thickness of the adhesive layer 65 is preferably small with respect to the wavelength of the radiation to be emitted from the semiconductor laser, so that the adhesive layer 65 does not have a significant disturbing influence on the resonator between the resonator surfaces 5. For example, a layer thickness of the adhesive layer is between 10 nm and 40 nm inclusive.

[0079] The adhesive layer 65 may also be applied to a coating 7 of the side face 25 (see FIG. 2A). For example, the coating 7 is a reflection reducing coating. For example, the reflectivity for the wavelength of maximum emission of the radiation emitted by the semiconductor laser 1 is at most 1%. This can further reduce the influence of the adhesive layer 65 on the optical properties of the semiconductor laser 1.

[0080] Furthermore, the semiconductor laser 1 shown in FIG. 5 has a reflection reducing coating 47 on the radiation exit surface 46 of the substrate body 45 as described in connection with FIG. 4. However, such a reflection reducing coating 47 is not absolutely necessary.

[0081] The exemplary embodiment shown in FIG. 6 corresponds essentially to the exemplary embodiment described in connection with FIGS. 1A and 1B. In contrast, a spacer 8 is arranged between the side face 25 of the semiconductor body 2 and the layer sequence 4. The layer sequence 4 is attached to the side face 25 via the spacer 8. As described above, the attachment can be made via a direct bonding connection or an adhesive layer.

[0082] A gap 85 is formed between the side face 25 and the layer sequence 4. The gap 85 is free of solid material and is filled, for example, by a gas, such as air. The width of the gap 85, i.e. the extent along the main radiation direction of the radiation, is expediently small compared to the wavelength of the radiation to be generated by the semiconductor laser. Thus, the reflection at the side face 25, i.e. the interface to the gap 85, can be reduced. If the spacer 8 is attached via an adhesive layer 65, the adhesive bond can be formed in such a way that the radiation does not have to be coupled out of the semiconductor laser through the adhesive layer.

[0083] The exemplary embodiment shown in FIG. 7 corresponds essentially to the exemplary embodiment described in connection with FIG. 6. In contrast, the spacer 8 is arranged to the side of the layer sequence 4. The spacer 8 and the layer sequence 4 are thus located next to each other on the substrate body 45. The layer sequence 4 is thus attached to the side face 25 via the substrate body 45.

[0084] The exemplary embodiment shown in FIG. 8 corresponds essentially to the exemplary embodiment described in connection with FIGS. 1A and 1B. In contrast, the semiconductor laser 1 is free of a substrate body 45 of the layer sequence 4. In this case, therefore, the layer sequence 4 itself forms the radiation exit surface of the semiconductor laser 1 when the layer sequence 4 forms the resonator mirror 5 at which the radiation is emitted during operation of the semiconductor laser 1.

[0085] FIGS. 9A to 9C describe an exemplary embodiment of a method for producing a semiconductor laser 1.

[0086] As shown in FIG. 9A, a semiconductor body 2 is provided, the semiconductor body having a plurality of resonator regions, the resonator regions 3 being arranged side by side along a lateral direction and each having an active region 20 provided for generating radiation (compare FIG. 1B).

[0087] FIG. 9B illustrates a layer sequence 4 that has been formed on a substrate body 45. For example, the layer sequences can be deposited by a PVD process and/or a CVD process and subsequently patterned. The deposition of dielectric layers and the patterning can also be repeated several times.

[0088] The subregions 40 are formed on the substrate body 45 with a center-to-center distance corresponding to the center-to-center distance of the resonator regions 3 of the semiconductor body 2 to which the layer sequence 4 is attached in a subsequent production step.

[0089] FIG. 9C illustrates the completed semiconductor laser 1 with the layer sequence 4 attached to a side face 25 of the semiconductor body 2, wherein the layer sequence 4 forms at least part of a resonator mirror 5 for at least one resonator region, in the exemplary embodiment shown for each of the four resonator regions.

[0090] The method is exemplified by the production of a semiconductor laser 1 formed as described in connection with FIGS. 1A and 1B.

[0091] However, the method can also be modified to produce the semiconductor lasers 1 described in connection with the other exemplary embodiments or other semiconductor lasers. For example, the layer sequence 4 may be attached to the side face 25 of the semiconductor body 2 by an adhesive layer instead of by a direct bond. Further, the substrate body 45 may be removed, for example, even before the layer sequence 4 is attached to the side face 25 of the semiconductor body 2.

[0092] The substrate-less layer sequence 4 can be pressed against the side face 25 by a transfer process, for example.

[0093] With the described method, a layer sequence 4 can be formed separately from the semiconductor bodies 2 of the semiconductor laser 1, which has different reflection profiles for individual resonator regions 3 of the semiconductor laser 1. The reflection profiles can be checked even before they are attached to the semiconductor laser. Furthermore, minor deviations in the emission wavelength of the semiconductor laser can be made by adjusting the separately produced layer sequence without having to change the production of the semiconductor body 2 per se.

[0094] The invention is not limited by the description based on the exemplary embodiments. Rather, the invention encompasses any new feature as well as any combination of features, which in particular includes any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or exemplary embodiments.