Semiconductor laser diode

Abstract

To provide a semiconductor laser diode.SOLUTION: A semiconductor laser diode (100) includes a semiconductor laminate (2) having at least one active layer (3) and a web waveguide structure (9) having a web. The web extends in a longitudinal direction (93) from a light output surface (6) to a rear surface (7), and is delimited by web side surfaces (11) in a lateral direction (91) perpendicular to the longitudinal direction (93). The web has a first region (910) and a second region (920) adjacent to the first region in a vertical direction (92) perpendicular to the longitudinal and lateral directions. The web includes a first semiconductor material in the first region (910), and at least one second semiconductor material different from the first semiconductor material in the second region (920). The web has a first width (919) in the first region (910), and a second width (929) in the second region (920) larger than the first width (919).SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] A semiconductor laser diode is provided.

[0002] This application claims priority from German Patent Application No. 102017118477.5, the disclosure of which is incorporated herein by reference.

[0003] In laser diodes with a web waveguide structure, also known as a ridge, a refractive index jump between the ridge region and the material adjacent to the ridge results in lateral waveguiding during operation, which allows one or more laser modes to be formed laterally, particularly in the active region defined by the ridge. Electrical current is applied to the diode via contacts in the region above the ridge, which electrically inverts and pumps the active region, thereby enabling laser operation. In this case, one or more optical modes exponentially decay laterally outside the ridge region, while current within the ridge is limited by the sidewalls and can only diffuse downward due to the lateral conductivity of the material present there. To achieve an efficient device with a characteristic curve that is as linear as possible, it is necessary to achieve as much overlap between the pumping and mode regions as possible. However, dimensional changes in the ridge affect the mode characteristics and simultaneously the current conduction, significantly limiting the means for optimizing this overlap.

[0004] That is, the definition of the ridge usually determines the mode guiding and the current spreading simultaneously and interdependently, as described above. It is well known to vary the width of the electrical contact on the ridge in order to vary the local current application. However, in this case, the contact area, which is necessarily at least partially narrowed, has the disadvantage, inter alia, of increasing the operating voltage.

[0005] At least one object of certain embodiments is to provide a semiconductor laser diode.

[0006] This problem is solved by the subject matter of the independent claims. Advantageous embodiments and developments of the subject matter are characterized in the respective dependent claims and can be taken further from the following description and drawings.

[0007] According to at least one embodiment, the semiconductor laser diode comprises at least one active layer configured and arranged to generate light in an active region during operation. The active layer may in particular be part of a semiconductor stack comprising multiple semiconductor layers and have a main extension plane perpendicular to the layer arrangement direction of the semiconductor stack. For example, the active layer may have exactly one active region. The active region may be defined at least in part by contact surfaces comprising electrode layers of the semiconductor stack, i.e., at least in part by surfaces through which current is applied within the semiconductor stack and thus the active layer. The active region may also be defined at least in part by web waveguide structures, i.e., webs formed in the form of elongated ridges in the semiconductor material of the semiconductor stack. Furthermore, the active layer may comprise multiple active regions, which may be defined by a corresponding number of the above-mentioned measures. Although the features and embodiments described below mostly relate to semiconductor laser diodes having one active region in the active layer and thus exactly one corresponding web waveguide structure, the configurations described below also apply correspondingly to semiconductor laser diodes having multiple active regions in the active layer and thus multiple corresponding web waveguide structures.

[0008] According to another embodiment, a method for manufacturing a semiconductor laser diode includes manufacturing an active layer configured and arranged to generate light during operation of the semiconductor laser diode. In particular, the semiconductor layer stack including the active layer can be manufactured by an epitaxy process. The examples and features described above and below apply equally to the semiconductor laser diode and to the manufacturing method thereof.

[0009] According to another embodiment, the semiconductor laser diode has a light output surface and a back surface opposite the light output surface. The light output surface and the back surface may in particular be side surfaces of the semiconductor laser diode, particularly preferably side surfaces of the semiconductor layer stack, which may also be referred to as facets. Via the light output surface, the semiconductor laser diode can emit light generated in the active region during operation. The light output surface and the back surface can be provided with suitable optical coatings, in particular reflective or partially reflective layers, which can form an optical cavity for the light generated in the active layer. The active region can extend between the back surface and the light output surface along a direction referred to herein and hereinafter as the longitudinal direction. The longitudinal direction may in particular be parallel to the main extension plane of the active layer. The direction of the vertical arrangement of the layers, i.e., the direction perpendicular to the main extension plane of the active layer, is referred to herein and hereinafter as the vertical direction. The direction perpendicular to the longitudinal direction and perpendicular to the vertical direction is referred to herein and hereinafter as the transverse direction. Thus, the longitudinal and lateral directions allow the development of a plane parallel to the main extension plane of the active layer.

[0010] The semiconductor layer sequence can be formed in particular as an epitaxial layer sequence, i.e., an epitaxially grown semiconductor layer sequence. In this case, the semiconductor layer sequence can be formed, for example, based on InAlGaN. InAlGaN-based semiconductor layer sequences are particularly those in which epitaxially produced semiconductor layers generally have a layer sequence of different individual layers, which layer sequence is formed from the III-V compound semiconductor material system InAlGaN. x Al y Ga 1-x-y N [0≦x≦1, 0≦y≦1 and x+y≦1]. In particular, the active layer can be based on such a material. A semiconductor layer sequence having at least one active layer based on InAlGaN can emit electromagnetic radiation, for example, preferably in the ultraviolet to green wavelength range.

[0011] Alternatively or additionally, the semiconductor layer sequence can be based on InAlGaP, i.e. the semiconductor layer sequence comprises different individual layers, at least one of which, for example the active layer, is based on InAlGaP, a compound semiconductor material system of III-V. x Al y Ga 1-x-y P[0≦x≦1, 0≦y≦1 and x+y≦1]. A semiconductor layer sequence having at least one active layer based on InAlGaP can, for example, emit electromagnetic radiation having one or more spectral components preferably in the green to red wavelength range.

[0012] Alternatively or additionally, the semiconductor stack may include other III-V compound semiconductor materials, such as InAlGaAs-based materials, or II-VI compound semiconductor materials. In particular, an active layer including an InAlGaAs-based material may be configured to emit electromagnetic radiation having one or more spectral components in the red to infrared wavelength range. The II-VI compound semiconductor materials may include at least one element from the second main group elements, such as Be, Mg, Ca, or Sr, and an element from the sixth main group elements, such as O, S, or Se. Examples of II-VI compound semiconductor materials include ZnSe, ZnTe, ZnO, ZnMgO, CdS, ZnCdS, and MgBeO.

[0013] The active layer and in particular the semiconductor layer sequence including this active layer can be formed on a substrate. For example, the substrate can be formed as a growth substrate on which the semiconductor layer sequence is grown. The active layer and in particular the semiconductor layer sequence including this active layer can be produced by an epitaxy process, for example metalorganic vapor phase epitaxy (MOVPE) or molecular beam epitaxy (MBE). This can particularly mean that the semiconductor layer sequence is grown on the growth substrate. Furthermore, the semiconductor layer sequence can be provided with electrical contacts in the form of electrode layers. The growth substrate can also be removed after the growth process. In this case, the semiconductor layer sequence can be transferred, for example, after growth, onto a substrate formed as a carrier substrate. The substrate can comprise a semiconductor material, for example one of the above-mentioned compound semiconductor material systems or other materials. In particular, the substrate can comprise or consist of sapphire, GaAs, GaP, GaN, InP, SiC, Si, Ge, and / or ceramic materials, for example SiN or AlN.

[0014] The active layer may comprise, for example, a conventional pn junction, a double heterostructure, a single quantum well structure (SQW structure) or a multiple quantum well structure (MQW structure) or quantum dots for light generation. In addition to the active layer, the semiconductor layer stack may comprise other functional layers and regions, such as p-type or n-type doped charge carrier transport layers, i.e., electron transport layers or hole transport layers, undoped, p-type doped or n-type doped confinement layers, cladding layers or waveguide layers, barrier layers, planarizing layers, buffer layers, protective layers and / or electrode layers, and any combination thereof. Furthermore, additional layers, such as buffer layers, barrier layers and / or protective layers, may be provided perpendicular to the growth direction of the semiconductor layer stack, for example, around the periphery of the semiconductor layer stack, i.e., for example, on the side surfaces of the semiconductor layer stack.

[0015] According to another embodiment, the semiconductor layer stack has at least one web waveguide structure. If the semiconductor laser diode has a substrate on which the semiconductor layer stack is formed, the web waveguide structure is formed on the top surface of the semiconductor layer stack opposite the substrate. Even if the semiconductor laser diode does not have a substrate, the surface having the web waveguide structure will be referred to as the top surface here and below. The web waveguide structure can in particular be formed by a web-like, vertically extending raised region of the semiconductor layer stack, i.e., by a web extending vertically from the light output surface to the back surface, which protrudes vertically beyond the top surface region that is laterally adjacent to it. The web can be vertically adjacent to the web top surface and laterally defined by web side surfaces. The side surfaces that laterally define the web waveguide structure can in particular form a step-like profile together with the laterally adjacent top surface region of the top surface of the semiconductor layer stack. The terms "web-like region," "web," and "web waveguide structure" may be used synonymously below. The semiconductor layer sequence can also have a number of web-like regions that are arranged laterally and spaced apart from one another and extend in the longitudinal direction, for which the following characteristics apply accordingly:

[0016] According to another embodiment, the web has at least one first region and one second region that differ from each other in at least one characteristic selected from the group consisting of width, material, and lateral characteristics. The first and second regions can be arranged adjacent to each other, particularly vertically one above the other. In this case, the web can be formed entirely from one or more first regions and one or more second regions, thereby forming the web from the first and second regions.

[0017] According to another embodiment, the web comprises a first semiconductor material in the first region and at least one second semiconductor material different from the first semiconductor material in the second region. For example, the first region can be formed of the first semiconductor material. Alternatively, the first region can comprise at least one other semiconductor material in addition to the first semiconductor material. When the first region comprises different semiconductor materials, these materials can be formed as individual layers of the first region, thereby forming the first region as a stack including at least two semiconductor layers, at least one layer of which comprises the first semiconductor material. Furthermore, the second region can be formed of the second semiconductor material. Alternatively, the second region can comprise at least one other semiconductor material in addition to the second semiconductor material. If the second region comprises different semiconductor materials, these materials may in particular be formed as individual layers of the second region, whereby the second region may be formed by a stack comprising at least two semiconductor layers, at least one layer of which comprises the second semiconductor material.

[0018] According to another embodiment, the web has at least one heterointerface in the second region. The heterointerface can be formed, in particular, by two semiconductor layers arranged one above the other and containing different semiconductor materials. Correspondingly, the web can have at least two layers containing different semiconductor materials in the second region. By forming at least one heterointerface, the piezoelectric effect and the formation of a two-dimensional charge carrier gas at this interface can be utilized, thereby achieving an increase in current spreading. Particularly preferably, the second region has multiple heterointerfaces, which further amplifies or even maximizes current spreading due to the aforementioned effect. Thus, the web can have, for example, multiple semiconductor layers in the second region, where directly adjacent semiconductor layers each contain a different semiconductor material. In particular, the web can have, in the second region, a plurality of periodically consecutive sets of at least two semiconductor layers containing different semiconductor materials, where at least two sets of semiconductor layers can contain or consist of the second semiconductor material. By taking the above-mentioned measures, in particular by forming one or more heterointerfaces, the web has a superlattice structure, also called a "superlattice", in the second region, which has the above-mentioned effect of having a positive effect on the current spreading properties of the second region.

[0019] According to another embodiment, the web has a first width in a first region and a second width in a second region, where the region width may be any characteristic selected from a maximum width, an average width, and a width characteristic, i.e., a width variation depending on vertical position in each web region, where the width of the web waveguide structure is measured in the lateral direction. That is, the web is not formed with a uniform width, but has a width variation depending on vertical position in the web due to the different widths of the first and second regions.

[0020] According to another embodiment, the second width is greater than the first width. That is, the second region can preferably have a region that is wider than the entire first region, for example. The wider region can be a portion of the second region or the entire second region. In the latter case, the transition from the first region to the second region can be particularly stepped in width, so that the web side of the transition from the first region to the second region has a single step. Alternatively, the transition from the first region to the second region can be continuous in width, so that the first and second regions meet at the same width and the pitch from the second region to the first region gradually increases, resulting in a wider web. The web waveguide structure can include, at least in the second region, an obliquely extending web side.

[0021] For example, the web can have a second width in the second region that increases in the direction towards the active layer. Furthermore, the second region can be provided between the first region and the active layer, particularly preferably if its width increases in the direction towards the active layer. The second region can also form the base region of the web, i.e., the region where the web waveguide structure is in contact with the rest of the semiconductor layer stack. In particular in this case, it can be further advantageous if the semiconductor layer stack comprises a semiconductor layer between the active region and the web that is in direct contact with the second region and that contains the same semiconductor material as the second region.

[0022] Furthermore, the web can have a second width in the second region that decreases in the direction towards the active layer. Furthermore, particularly preferably, the first region can be located between the second region and the active layer, if the second width decreases in the direction towards the active layer. Furthermore, that is, particularly preferably, the second region can form an upper surface region of the web together with the upper surface of the web, in particular the vertically closed part of the web waveguide structure on the side facing away from the active layer.

[0023] According to another embodiment, the first region has a uniform first width. In other words, the first region has substantially the same width regardless of vertical position. Alternatively, the first region may have a varying first width. For example, the web may have an increasing width in the first region in a direction toward the active layer. Alternatively, the web in the first region may have a decreasing width in a direction toward the active layer. When the first and second regions each have a varying, in particular increasing, width, the change in width of the second region is preferably greater than the change in width of the first region.

[0024] As mentioned above, the web may have two or more first regions and / or two or more second regions. Particularly preferably, the web has two second regions and a first region disposed therebetween, each of the second regions having a second semiconductor material and a width greater than that of the first region. In this case, the two second regions can be formed equal or different in material and / or width, and each second region can have one or more of the above-mentioned characteristics. In particular, one of the two second regions can form the base region of the web waveguide structure, and the other of the two second regions can form the top region of the web.

[0025] According to another embodiment, the web has a web height in the vertical direction. The web height may in particular be the vertical distance from the top surface of the web to a top surface region of the top surface of the semiconductor layer sequence that is laterally adjacent to the web. Correspondingly, the first region may have a first height and the second region may have a second height in the vertical direction. Particularly preferably, the second region may have a second height in the vertical direction that is 2% to 65% of the web height. The web height may typically be in the range of 500 nm, and the second height may typically, particularly preferably, be in the range of about 80 nm.

[0026] According to another embodiment, the web has a maximum first width B in the first region. max,1 and the second region has a maximum second width B max,2and the magnitude of the lateral setback from the second region to the first region is ΔB=(B max,2 -B max,1 ) / 2 Here, preferably 0.01%≦(ΔB / B max,1 )≦20%, Particularly preferably 0.02%≦(ΔB / B max,1 )≦10% The above holds. A particularly preferred value of the first width may be 1 μm or more and 3 μm or less, typically about 2 μm. Furthermore, ΔB may preferably be 2 nm or more, or 10 nm or more, or 15 nm or more, and may be 1 μm or less, or 300 nm or less, or 150 nm or less.

[0027] According to another embodiment, the web side surface of the second region, or at least a part of it, is inclined at an angle α relative to a plane extending in the longitudinal and transverse directions, preferably 20°≦α≦100°, more preferably 20°≦α≦90°. In other words, the web side surface, at least partially in the second region, forms a slope inclined by the aforementioned angle α relative to a top surface region of the semiconductor layer sequence that laterally borders the web waveguide structure. Thus, an angle α=90° for at least a part of the second region means that the web side surface in this region is perpendicular to the aforementioned plane extending in the longitudinal and transverse directions. The side surface or part of the side surface that forms an angle α<90° or α>90° is also referred to here and below as an oblique side surface.

[0028] According to another embodiment, the semiconductor layer sequence is based on nitride semiconductor material, i.e. InAlGaN, which may also include InGaN, AlGaN and GaN. In this case, the first semiconductor material may particularly preferably comprise or be AlGaN, and the second semiconductor material, which is different from the first semiconductor material, may be AlGaN. x In y Ga 1-x-y N[0≦x≦0.2 and 0≦y≦0.2].

[0029] In the semiconductor laser diodes described herein, according to the above-described embodiments, a portion of the web waveguide structure, i.e., a portion of the ridge, can be fabricated as a superlattice comprising multiple epitaxial layers, with the superlattice region having a different width and shape than the other regions, sometimes referred to as the "bulk" or "ridge bulk" of the web waveguide structure. The region configured as a superlattice can preferably be, for example, angled or stepped, as described above. This allows for the desired adjustment of the mode characteristics of the laser diode and the overlap of the mode region with the electrical pumping region or current spreading region within the laser diode. This allows for semiconductor laser diodes with low lasing thresholds, high efficiency, and very linear characteristic curves. The ease of passivation coating of the web waveguide structure, even at the angled edges, provides an additional advantage, allowing for high quality and yields to be achieved.

[0030] Further advantages, advantageous embodiments and developments result from the respective examples described below in conjunction with the figures. [Brief explanation of the drawings]

[0031] [Figure 1] 1A and 1B are schematic diagrams showing a semiconductor laser diode according to an embodiment. [Figure 2] 10A and 10B are schematic diagrams showing a semiconductor laser diode according to another embodiment. [Figure 3] FIG. 10 is a schematic diagram illustrating a portion of a semiconductor laser diode according to another embodiment. [Figure 4] FIG. 10 is a schematic diagram illustrating a portion of a semiconductor laser diode according to another embodiment. [Figure 5] FIG. 10 is a schematic diagram illustrating a portion of a semiconductor laser diode according to another embodiment. [Figure 6] FIG. 10 is a schematic diagram illustrating a portion of a semiconductor laser diode according to another embodiment. [Figure 7]FIG. 10 is a schematic diagram illustrating a portion of a semiconductor laser diode according to another embodiment. [Figure 8] FIG. 10 is a schematic diagram illustrating a portion of a semiconductor laser diode according to another embodiment. [Figure 9] FIG. 10 is a schematic diagram illustrating a portion of a semiconductor laser diode according to another embodiment. [Figure 10] FIG. 10 is a schematic diagram illustrating a portion of a semiconductor laser diode according to another embodiment. [Figure 11] FIG. 10 is a schematic diagram illustrating a portion of a semiconductor laser diode according to another embodiment. [Figure 12] FIG. 10 is a schematic diagram illustrating a portion of a semiconductor laser diode according to another embodiment.

[0032] In the various embodiments of the figures, the same reference numerals may be used to designate identical, similar, or functionally similar elements. The dimensions of the illustrated elements and their respective relative dimensions are not to scale; rather, individual elements, e.g., layers, modules, elements, regions, etc., may be intentionally enlarged for better illustration and / or understanding.

[0033] 1A and 1B show an example of a semiconductor laser diode 100, with FIG. 1A showing a cross-sectional view of the semiconductor laser diode 100 parallel to a horizontal direction 91 and a vertical direction 92, and FIG. 1B showing a cross-sectional view of the semiconductor laser diode 100 parallel to a vertical direction 92 and a vertical direction 93. In the following description, reference will also be made to FIGS. 1A and 1B. Note that the following description relates to a preferred embodiment of a semiconductor laser diode based on a nitride semiconductor material, i.e., InAlGaN, but the above-described embodiments and features also apply correspondingly to semiconductor laser diodes based on other compound semiconductor material systems.

[0034] The semiconductor laser diode 100 has a substrate 1, which serves as a growth substrate for a semiconductor layer sequence 2, which is epitaxially grown on top of it. Alternatively, the substrate 1 may be a carrier substrate onto which the semiconductor layer sequence 2, grown on the growth substrate, is transferred after growth. For example, the substrate 1 may be formed of GaN grown on a semiconductor layer sequence 2 based on InAlGaN compound semiconductor material. Other materials are also possible for the substrate 1 and the semiconductor layer sequence 2, as described in particular in the Background section. Furthermore, the semiconductor laser diode 100 may not have a substrate. In this case, the semiconductor layer sequence 2 may be grown on a growth substrate and subsequently removed. The semiconductor layer sequence 2 includes an active layer 3 configured to generate light 8 during operation, in particular laser light, when a lasing threshold is exceeded, and to emit this light via a light output surface 6.

[0035] 1A and 1B, the direction extending parallel to the main extension direction of the layers of the semiconductor stack 2, for example when viewing the light output surface 6 from above, is referred to here and hereinafter as the lateral direction 91. The direction in which the layers of the semiconductor stack 2 are arranged vertically and the direction in which the semiconductor stack 2 is disposed on the substrate 1 is referred to here and hereinafter as the vertical direction 92. The direction perpendicular to the lateral direction 91 and the vertical direction 92 and along the radiation direction of the light 8 is referred to here and hereinafter as the longitudinal direction 93.

[0036] The side of the semiconductor stack 2 opposite the substrate 1, which forms the top surface of the device 100, is provided with an electrode layer 4 arranged and configured for electrical connection of the semiconductor stack 2. The electrode layer 4 may comprise, for example, one or more of the following metals or materials: Ag, Al, Au, Pt, Pd, Ni, Rh, Ti, ITO. The semiconductor laser diode 100 may have another electrode layer for electrical connection of another side of the semiconductor stack 2, which is not shown for clarity.

[0037] The semiconductor stack 2 may include other semiconductor layers in addition to the active layer 3, such as a cladding layer, a waveguide layer, a barrier layer, a current spreading layer, and / or a current limiting layer, but these are not shown for simplicity. For example, the semiconductor stack 2 has a buffer layer on the substrate 1, a first cladding layer thereon, and a first waveguide layer thereon, with the active layer 3 provided on the first waveguide layer. At least one second waveguide layer, a second cladding layer, and a semiconductor contact layer may be formed on the active layer 3. If the semiconductor stack 2 is based on an InAlGaN compound semiconductor material as described above, for example, the buffer layer may contain or be made of undoped or n-type doped GaN, the first cladding layer may contain or be made of n-type doped AlGaN, the first waveguide layer may contain or be made of n-type doped GaN, the second waveguide layer may contain or be made of p-type doped GaN, the second cladding layer may contain or be made of p-type doped AlGaN, and the semiconductor contact layer may contain or be made of p-type doped GaN. The n-type doped material may be Si, for example, and the p-type doped material may be Mg, for example. The active layer 3 may be formed by a pn junction or a multi-layer quantum well structure, for example, by alternating layers containing or made of InGaN and layers containing or made of GaN. In such a semiconductor stack, the substrate may contain or be made of n-type doped GaN, for example.

[0038] The top surface of the semiconductor layer sequence 2, facing away from the substrate 1, except for the contact area of ​​the semiconductor layer sequence 2 with the electrode layer 4, is covered by a passivation material 19, which may for example comprise or be formed from an electrically insulating oxide, nitride or oxynitride, such as silicon dioxide, silicon nitride, silicon oxynitride, aluminum oxide, tantalum oxide, rhodium oxide, niobium oxide and / or titanium dioxide. Other oxides, nitrides or oxynitrides are also possible, including one or more materials selected from Al, Ce, Ga, Hf, In, Mg, Nb, Rh, Sb, Si, Sn, Ta, Ti, Zn, Zr.

[0039] Furthermore, on the light output surface 6 and on the opposite side, on the back surface 7 which forms the side of the semiconductor stack 2 and the substrate 1, a reflective layer or reflective layer body or a partially reflective layer or partially reflective layer body can be formed, which are not shown for clarity but are arranged and configured to form an optical cavity within the semiconductor stack 2.

[0040] On the top surface of the semiconductor layer stack 2 facing away from the substrate 1, a web waveguide structure 9 is formed by removing a portion of the semiconductor material from the surface of the semiconductor layer stack 2 facing away from the substrate 1. Here, the top web surface 10 forms the top-side contact area of ​​the semiconductor layer stack 2 with the electrode layer 4. The web waveguide structure 9 extends in a longitudinal direction 93 and is bounded on both sides in a lateral direction 91 by web side surfaces 11. The web side surfaces 11 and the remaining top surface of the semiconductor layer stack 2 that laterally adjoins the web side surfaces 11 are covered with the above-mentioned passivation material 19. The refractive index jump at the web side surfaces 11, which is caused by the transition from the semiconductor material to the passivation material 19, allows so-called index guiding of the light generated in the active layer 3 to occur. This is crucial for the formation of the active region 5 in the semiconductor layer stack 2, which represents the region where the generated light is guided and amplified in laser operation.

[0041] 1A, the web waveguide structure 9 can be formed by completely removing the semiconductor material on both lateral sides of the web. Alternatively, a so-called "tripod" configuration is possible, in which the semiconductor material is removed only along two channels lateral to the web.

[0042] The following figures, which illustrate portions of the semiconductor laser diode 100 in cross section as shown in FIG. 1A, will explain the features of the web waveguide structure 9 described above in the context of alternative embodiments. Therefore, the following description will primarily relate to variations of the web waveguide structure 9 of the semiconductor laser diode 100 described in connection with FIGS. 1A and 1B. Therefore, for clarity, the following figures do not show, in particular, the electrode layer 4 and passivation material 19, which preferably contact the entire web top surface 10 as shown in FIG. 1A.

[0043] 2A and 2B show an embodiment of a semiconductor laser diode 100 having a web waveguide structure 9 with a first region 910 and a second region 920 arranged vertically one above the other and adjacent to each other. The first region 910 and the second region 920, as in the following embodiments, differ in width and / or material and / or lateral characteristics. In the embodiment of FIG. 2A and 2B, the first region 910 and the second region 920 differ in all of the characteristics mentioned herein.

[0044] The first region 910 comprises at least one semiconductor layer 911 having a first semiconductor material, and the second region 920 comprises at least one semiconductor layer 921 having a second semiconductor material different from the first semiconductor material. For the nitride semiconductor material system described with respect to this embodiment, the first semiconductor material of the first region 910 may particularly preferably comprise or be formed from AlGaN. The second semiconductor material of the second region 920 may particularly preferably comprise AlGaN. x In y Ga 1-x-yN [0≦x≦0.2 and 0≦y≦0.2]. For example, the second region 920 can include GaN or InGaN as the second semiconductor material. In addition to the semiconductor layer 911, the first region 910, in the illustrated embodiment, includes another semiconductor layer 912 forming a semiconductor contact layer, which contacts the upper surface 10 of the web and thus the upper surface of the semiconductor stack 2 with the upper electrode layer. In other words, the first region 910 includes a different semiconductor material in addition to the first semiconductor material. Similarly, in the illustrated embodiment, the second region 920 includes at least one other semiconductor material in addition to the second semiconductor material. The second semiconductor material and the different semiconductor material of the second region 920 include or are AlInGaN having a composition different from that of the second semiconductor layer 921, but are formed as semiconductor layers 921 and 922, respectively. That is, as shown, the web waveguide structure 9 includes, in the illustrated embodiment, multiple semiconductor layers 921, 922 arranged alternately within the second region 920, such that directly adjacent semiconductor layers in the second region 920 include different semiconductor materials. This periodic sequence of at least two semiconductor layers 921, 922, each including a different semiconductor material, forms a superlattice with multiple heterointerfaces, which can improve current spreading, as discussed above in the Background of the Invention section. Instead of the illustrated first region 910 and second region 920 each including multiple semiconductor layers, the first region 910 and second region 920 can also be formed solely from the above-mentioned first semiconductor material or solely from the above-mentioned second semiconductor material.

[0045] The second region 920 is provided between the active layer 3 and the first region 910 and forms a base region of the web waveguide structure 9. The second region 920 of the web waveguide structure 9 therefore borders on that part of the semiconductor layer sequence 2 which does not belong to the web waveguide structure 9, so that the second region 920 forms a step profile on the top surface of the semiconductor layer sequence 2 in the laterally bordering top surface region. In particular in this case, it may be advantageous if the semiconductor layer sequence 2 comprises, as shown, a semiconductor layer 21 between the active layer 3 and the web waveguide structure 9 which directly borders the second region 920 and which has the same semiconductor material as the second region 920. In other words, the second region 920 comprises at least one semiconductor layer which comprises the same material as the semiconductor layer 21. In particular, the semiconductor layer in the second region 920 may be the lowest semiconductor layer in the second region when viewed from the active layer, and therefore the semiconductor layer in the second region containing the same semiconductor material as the semiconductor layer 21 may be in direct contact with the semiconductor layer 21. Therefore, the lowest semiconductor layer in the second region 920 and the semiconductor layer 21 may intersect with each other without a discernible layer boundary.

[0046] The web waveguide structure 9 may further be configured such that it does not have a uniform width, but rather has a width that varies depending on the vertical position. In particular, the web waveguide structure 9 has a first width 919 in the first region 910 and a second width 929 in the second region 920. The widths of the regions are their respective maximum widths in the illustrated embodiment, as shown in FIG. 2A. Alternatively, an average width or respective width characteristics may be used. In particular, the second width 929 of the second region 920 is greater than the first width 919 of the first region 910, so that the second region 920 is wider than the first region 910 in at least one region, or substantially entirely as shown, and the first region 910 and the second region 920 abut each other at a location of equal width. The maximum width of the first region 910, i.e., the first width 919 in the illustrated embodiment, is defined as B. max,1 , the maximum width of the second region 920, i.e., the second width 929 in the illustrated embodiment, is B max,2 When ΔB=(B max,2 -B max,1 ) / 2 is the size of the setback from the second region 920 to the first region 910. The widths mentioned above are preferably 0.01%≦(ΔB / B max,1 )≦20%, Or particularly preferably 0.02%≦(ΔB / B max,1 )≦10% In this case, the first width 919 may preferably be 0.5 μm or more and 100 μm or less, and particularly preferably 1 μm or more and 50 μm or less. Also, 2 nm≦ΔB≦1000 nm, or preferably 10 nm≦ΔB≦300 nm, or particularly preferably 15 nm≦ΔB≦150 nm may be satisfied.

[0047] Furthermore, the web waveguide structure 9 has inclined web side faces in the second region 920, so that the width of the web waveguide structure 9 in the second region 920 increases continuously in at least one region in the direction towards the active layer 3. The web side faces 11 form a slope in part of the second region, which slope is inclined by an angle 930, shown in FIG. 2A, with respect to a plane formed by the top surface region of the semiconductor layer sequence that laterally borders the web waveguide structure 9. The angle 930 may preferably be between 20° and 100°, particularly preferably 90° or less. In contrast, the first region 910 has a uniform width 919 in the illustrated embodiment.

[0048] The web waveguide structure 9 described above further has a web height 90. It has been found that the base region of the web waveguide structure 9 formed by the second region 920 preferably has a second height 923 in the range of 2% to 65% of the web height 90. For example, the web height 90 may be approximately 500 nm, while the second height 923 may be approximately 80 nm, in a particularly preferred embodiment.

[0049] To fabricate the web waveguide structure 9 described above, for example, one or more suitable etching processes can be performed, with parameters set to form the above-described structure. By using such an etching process, the current application in the region of the web waveguide structure 9 can be tailored to optimize current spreading toward the active layer. As described above, the current spreading region is formed as a superlattice region, which in the illustrated embodiment includes multiple AlInGaN layers with different compositions. In this way, the piezoelectric effect and the formation of a two-dimensional charge carrier gas at the interface can be utilized to achieve maximum current spreading without significantly affecting mode guiding. This allows for the intentional tuning of lateral mode dispersion and current spreading to achieve optimal overlap. To this end, FIG. 2B shows a lateral laser mode 990 and a current flow 991, the latter of which is distinctly spread by the above-described structure in the web waveguide structure 9. Tailoring the mode pattern and current spreading can result in high efficiency, low threshold current, and linear characteristics.

[0050] The following figures illustrate modifications of the embodiments described in connection with Figures 2A and 2B. Therefore, the descriptions of the following figures primarily relate to differences from the preceding embodiments. Other than the differences described, the embodiments of the following figures may have features of the preceding embodiments, even if not all features are explicitly shown.

[0051] 3 shows an embodiment in which the web waveguide structure 9 has a width that decreases in the direction towards the active layer 3 in a second region 920, which can be formed similarly to the previous embodiment. Also, the first region 910 is now provided between the second region 920 and the active layer 3, so that the second region 920 forms the top region of the web waveguide structure 9.

[0052] The embodiment of Figure 4 is a combination of the embodiments shown in Figures 2A and 2B and 3. The web waveguide structure 9 of this embodiment has two second regions 920 formed as described above and separated by a first region 910. The two second regions 920 may be formed identically or differently in terms of material and / or width.

[0053] Unlike the embodiments shown in Figures 2A to 4, in which the first regions 910 are each formed with a uniform first width 919, the width of the first regions can also vary depending on the vertical position, as shown in Figures 5 and 6. For example, the web waveguide structure 9 can widen (Figure 5) or narrow (Figure 6) in the first regions 910 in the direction toward the active layer 3, with the angle selected such that the corresponding slope of the web side surface 11 in the first regions 910 is smaller than the slope in the second regions 920, and the web waveguide structure 9 can otherwise be formed preferably in the same manner as described in connection with Figures 2A and 2B or 3. Furthermore, as shown in Figures 7 to 9, the second regions 920 can be formed by non-sloped web sides, have a uniform width, and form a step together with the first regions 910, so that the transition from the first regions 910 to the second regions 920 is stepped in width.

[0054] The semiconductor layers 921, 922 in the second region 920 can each have equal or different thicknesses, and as shown in the partial view of Figure 10, the semiconductor layers 921, 922 can vary in pitch and thickness as well as composition.

[0055] 11 and 12 show another embodiment in which the second regions 920, which can be formed with stepped or oblique web flanks, respectively have exactly one heterointerface compared to the previous embodiment, i.e. exactly two semiconductor layers 921, 922, each comprising different semiconductor materials. Furthermore, it is also possible for the second regions 920 to have exactly one semiconductor layer of the semiconductor layer sequence that forms a heterointerface with the semiconductor layer that borders the web waveguide structure 9, i.e. the semiconductor layer that laterally borders the web waveguide structure 9 and forms the top surface of the semiconductor layer sequence 2.

[0056] The illustrated embodiments and features are not limited to the respective combinations shown. Rather, the illustrated embodiments and individual features can be combined with each other, even if not all possible combinations are explicitly stated. Furthermore, the illustrated embodiments may alternatively or additionally include further features as described in the Background section.

[0057] The present invention is not limited to the specific embodiments described, but rather includes all novel features and combinations thereof, and thus specifically includes all combinations of features in the claims, even if the novel feature or combination itself is not explicitly set forth in the claims or in the specific embodiments. [Explanation of symbols]

[0058] 1 board 2. Semiconductor laminate 3 Active layer 4 electrode layer 5 Active area 6 Light output surface 7 Back 8 light 9. Web Waveguide Structure 10 Web top 11 Web Side 19 Passivation Materials 21,911,912,921,922 Semiconductor layer 910 First Area 919 First Width 920 Second Realm 923 height 929 Second Width 930 angle 90 web height 91 Horizontal 92 Vertical 93 Vertical 100 Semiconductor laser diode 990 Laser Mode 991 Current Flow

Claims

1. A semiconductor laser diode (100), The semiconductor layer stack (2) has at least one active layer (3) and a web waveguide structure (9) having a web, the web extending in a longitudinal direction (93) from a light output face (6) to a rear face (7) and being defined by web sides (11) in a transverse direction (91) perpendicular to the longitudinal direction (93), The web has a first region (910) and a second region (920) bordering the first region in a vertical direction (92) perpendicular to the machine direction and the cross direction; the web comprises a first semiconductor material in the first region (910) and at least one second semiconductor material in the second region (920) that is different from the first semiconductor material; the web has a first width (919) in the first region (910); the web has a second width (929) in the second region (920) that is greater than the first width (919); the first region and the second region have varying widths, the variation in width of the second region being greater than the variation in width of the first region; The active layer (3) is disposed below the web waveguide structure (9) in a plan view of the web waveguide structure (9) and spaced apart from the web waveguide structure (9). A semiconductor laser diode (100).

2. the transition from the first region (910) to the second region (920) is stepped; The semiconductor laser diode (100) of claim 1.

3. the webs have a width in the second region (920) that increases in a direction towards the active layer (3); The semiconductor laser diode (100) according to claim 1 or 2.

4. The second region (920) is located between the first region (910) and the active layer (3); The semiconductor laser diode (100) according to any one of the preceding claims.

5. the second region (920) forming a base region of the web; The semiconductor laser diode (100) according to any one of the preceding claims.

6. The semiconductor laminate (2) has a semiconductor layer (21) between the active layer (3) and the web, the semiconductor layer (21) being in direct contact with the second region (920) and containing the same semiconductor material as the second region (920). The semiconductor laser diode (100) according to any one of the preceding claims.

7. the webs have a width in the second region (920) that decreases in a direction towards the active layer (3); The semiconductor laser diode (100) according to claim 1 or 2.

8. The first region (910) is located between the second region (920) and the active layer (3); The semiconductor laser diode (100) of claim 7.

9. the second region (920) forming a top surface region of the web; The semiconductor laser diode (100) according to claim 7 or 8.

10. the web has at least one heterointerface in the second region (920); The semiconductor laser diode (100) according to any one of the preceding claims.

11. the web has at least two layers (921, 922) in the second region (920) comprising different semiconductor materials; The semiconductor laser diode (100) according to any one of the preceding claims.

12. the web has, in the second region (920), a periodic sequence of at least two layers (921, 922); The semiconductor laser diode (100) according to any one of the preceding claims.

13. the webs have a width in the first region (910) that increases in a direction towards the active layer (3); The semiconductor laser diode (100) according to any one of the preceding claims.

14. the webs have a width in the first region (910) that decreases in a direction towards the active layer (3); The semiconductor laser diode (100) according to any one of the preceding claims.

15. the web has a web height (90) in the vertical direction (92); The second region (920) has a height (923) in the vertical direction (92) that is greater than or equal to 2% and less than or equal to 65% of the web height. The semiconductor laser diode (100) according to any one of the preceding claims.

16. The web has a maximum first width B in the first region (910). ｍａｘ，１ and a maximum second width B ｍａｘ，２ where ΔB=(B ｍａｘ，２ -B ｍａｘ，１ ) / 2 And, 0.01%≦ΔB / B ｍａｘ，１ ≦20% holds true. The semiconductor laser diode (100) according to any one of the preceding claims.

17. 2 nm≦ΔB≦1000 nm holds true. The semiconductor laser diode (100) of claim 16.

18. In said second region (920), said web side (11) is inclined at an angle α to a plane extending in said transverse direction (91) and said longitudinal direction (93), where: ２０°≦α≦１００° holds true. The semiconductor laser diode (100) according to any one of the preceding claims.

19. The first semiconductor material includes AlGaN, and the second semiconductor material, which is different from the first semiconductor material, includes AlGaN. ｘ In ｙ G １－ｘ－ｙ N [0≦x≦0.2 and 0≦y≦0.2], The semiconductor laser diode (100) according to any one of the preceding claims.

20. In the second region (920), the web comprises a structure of a superlattice including InAlGaN layers having different compositions. The semiconductor laser diode (100) according to any one of the preceding claims.

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