Semiconductor laser device and its manufacturing method

Abstract

To provide a semiconductor laser device which contributes to an improvement in visibility or image quality.SOLUTION: A semiconductor laser device LD0 comprises a substrate 1, a first clad layer 2 of a first conductivity type, a second clad layer 3 of a second conductivity type, and a light-emitting layer EL. The semiconductor laser device also comprises: at least two, first and second light-emitting parts EM01 and EM02 formed in the light-emitting layer EL and radiating laser beams; an optical waveguide OW extending in a resonator direction; and an adjustment region AR adjusting a beam form of the laser beams. Further, the adjustment region AR is formed at least at a light emission end face side of the optical waveguide and includes a first adjustment region AR01 and a second adjustment region AR02. A first wavelength λ01 of a first laser beam radiated from the first light-emitting part EM01 is different from a second wavelength λ02 of a second laser beam radiated from the second light-emitting part EM02, and respective lengths of the first and second adjustment regions AR01 and AR02 in the resonator direction are different.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a semiconductor laser device. [Background technology]

[0002] 2. Description of the Related Art In recent years, the market for display devices such as projectors using semiconductor laser devices (hereinafter simply referred to as "semiconductor LD" or "LD") has been expanding.

[0003] Furthermore, reality technologies such as Augmented Reality (AR), Virtual Reality (VR), Mixed Reality (MR), and Substitutional Reality (SR) have been put to practical use in various fields, and display devices using these technologies, such as Head Mounted Displays (HMDs), Head-up Displays, and AR glasses, have been commercialized.

[0004] For example, in a head mounted display (HMD), a technology is known in which three colors of laser light, RGB (red, green, and blue), are used as the light source, an image is created by a MEMS (Micro Electro Mechanical System), which is a spatial modulation element for image display, and projected onto the retina or the like through a waveguide. This system using MEMS is said to have advantages such as a wide color gamut, high resolution, and wide viewing angle. On the other hand, in order to further improve image quality such as a wide color gamut, high resolution, and wide viewing angle, multi-beam LDs (multiple semiconductor laser devices) were used for each color of RGB, but the wavelengths of each color were the same. If the wavelengths of all the beams were the same (i.e., if the wavelengths were the same), the image quality would deteriorate due to the coherence of the laser light.

[0005] Patent Document 1 discloses a multi-wavelength semiconductor laser capable of oscillating lasers of multiple wavelengths within the same element. Patent Document 1 does not disclose the specific wavelength of the laser light, but since it is an AlGaAs-based quantum well laser, it describes laser light in the infrared region and in a color region other than RGB. In addition, the first and second quantum well active layers oscillating different wavelengths have different well widths (physical film thicknesses). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 05-082894 Summary of the Invention [Problem to be solved by the invention]

[0007] In addition to the above technical background, in order to improve image quality (resolution and frame rate), there is a demand for a monolithic single-mode lateral laser diode that independently drives a multi-emitter (multiple light-emitting parts) with a narrow pitch. However, the single-mode lateral laser diode has a narrow wavelength spectrum and high coherence, which causes degradation of image quality.

[0008] Moreover, in order to improve the performance of display devices, there is a demand for suppressing interference of laser light and further improving visibility and image quality such as a wide color gamut, high resolution, and wide viewing angle. In order to further improve visibility and image quality, for example, a semiconductor laser device capable of emitting a plurality of laser beams with different oscillation wavelengths for each color of a light source using three colors of laser light, RGB, is preferable from the viewpoint of suppressing deterioration in image quality due to the above-mentioned coherence of laser light.

[0009] However, the present inventors have found the following. In order to emit laser light of a plurality of wavelengths with different oscillation wavelengths, it is conceivable to change the band gap energy of the light emitting layer (active layer) of each light emitting section that emits each laser light. For this purpose, for example, by changing the film thickness of the light emitting layer, or the composition of the light emitting layer without changing the film thickness of the light emitting layer, for each light emitting section, laser light of a plurality of different wavelengths can be obtained. However, as a result of the intensive research of the present inventors, it has been found that if the wavelength of the laser light differs for each light emitting section, a difference occurs in the beam shape of the laser light emitted from each light emitting section. This is thought to be because, when the wavelength of the laser light differs, the equivalent refractive index felt by each laser light propagating in the optical waveguide changes, and as a result, a difference occurs in the beam shape of each laser light. And, if such a difference in the beam shape occurs (or if the deviation of each beam shape becomes large), it can be one of the causes of deterioration of visibility and image quality. In addition, if the beam shape and beam spread angle of the laser light emitted from the light-emitting end face of the LD differ for each laser light, problems caused by differences in beam shape can be corrected to some extent by designing and adjusting the optical system, such as the lens that receives the beam, for each beam. However, this is not only extremely time-consuming, but also leads to increased costs.

[0010] The above-mentioned Patent Document 1 does not mention anything about the beam shapes of the laser beams and the differences therebetween due to differences in emission wavelength.

[0011] It is an object of the present invention to provide a semiconductor laser device which contributes to improving visibility and image quality. Other objects and novel features will become apparent from the description of this specification and the drawings. [Means for solving the problem]

[0012] A semiconductor laser device according to an embodiment includes a substrate, a first cladding layer of a first conductivity type and a second cladding layer of a second conductivity type laminated on a main surface of the substrate, and a light emitting layer sandwiched between the first cladding layer and the second cladding layer and formed on a first surface parallel to the main surface of the substrate. The semiconductor laser device also includes at least two first and second light emitting sections formed in the light emitting layer and emitting laser light, an optical waveguide formed of the light emitting layer, the first cladding layer, and a part of the second cladding layer and extending in a resonator direction, and an adjustment region for adjusting the beam shape of the laser light emitted from the first and second light emitting sections. Furthermore, the adjustment region is formed at least on the light emitting end surface side of the optical waveguide, and includes a first adjustment region formed in the first light emitting section and a second adjustment region formed in the second light emitting section. Further, the first and second adjustment regions are formed in the light-emitting layer corresponding to at least the first and second light-emitting portions, respectively, a first wavelength of a first laser light emitted from the first light-emitting portion is different from a second wavelength of a second laser light emitted from the second light-emitting portion, and the first and second adjustment regions have different lengths in the resonator direction. Effect of the Invention

[0013] In the semiconductor laser device according to one embodiment, it is possible to provide a semiconductor laser device that contributes to improving visibility and image quality. [Brief description of the drawings]

[0014] [Figure 1] 1 is a perspective view showing a main part of an example of a configuration of a semiconductor laser device according to a preferred embodiment. [Diagram 2] 1 is a perspective view showing an example of a configuration of a main part of a semiconductor laser device according to a first embodiment. [Diagram 3] 1 is a top view of a main portion showing a configuration of a semiconductor laser device according to a first embodiment. [Figure 4] 2 is a cross-sectional view showing an example of a configuration of a main part of light-emitting layers EL11 to EL13 in the semiconductor laser device according to the first embodiment. [Diagram 5]FIG. 1 is an explanatory diagram (1) relating to the beam shape (NFP / FFP) of laser light. [Figure 6] FIG. 2 is an explanatory diagram (2) relating to the beam shape (NFP / FFP) of laser light. [Figure 7A] 4 is an explanatory diagram showing an improvement result of the beam shape (NFP) of the laser light in the semiconductor laser device according to the first embodiment. FIG. [Figure 7B] 4 is a graph showing an improvement result of the beam shape (NFP) of the laser light in the semiconductor laser device according to the first embodiment. [Figure 7C] 4 is a graph showing an improvement result of the beam shape (FFP) of the laser light in the semiconductor laser device according to the first embodiment. [Figure 8] 3 is a cross-sectional view of a main part illustrating an example of a process included in a manufacturing method of the semiconductor laser device according to the first embodiment. [Figure 9] 3 is a cross-sectional view of a main part illustrating an example of a process included in a manufacturing method of the semiconductor laser device according to the first embodiment. [Figure 10] 3 is a cross-sectional view of a main part illustrating an example of a process included in a manufacturing method of the semiconductor laser device according to the first embodiment. [Figure 11] 3 is a cross-sectional view of a main part illustrating an example of a process included in a manufacturing method of the semiconductor laser device according to the first embodiment. [Figure 12] 3 is a cross-sectional view of a main part illustrating an example of a process included in a manufacturing method of the semiconductor laser device according to the first embodiment. [Figure 13] 3 is a cross-sectional view of a main part illustrating an example of a process included in a manufacturing method of the semiconductor laser device according to the first embodiment. [Figure 14] 11A and 11B are a top view and a cross-sectional view of a main portion showing a configuration of a semiconductor laser device according to a second embodiment. [Figure 15] 11 is an explanatory diagram showing a distribution of laser light near an optical waveguide in a semiconductor laser device according to a second embodiment. FIG. [Figure 16] 11A and 11B are a top view and a cross-sectional view of a main portion showing a configuration of a semiconductor laser device according to a third embodiment. [Figure 17] 11 is a top view of a main part showing a configuration of a semiconductor laser device according to a fourth embodiment. FIG. [Figure 18] 13 is an explanatory diagram showing the operation of the semiconductor laser device according to the fourth embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the semiconductor laser device according to the embodiment will be described in detail with reference to the drawings. In the specification and the drawings, the same or corresponding components are given the same reference numerals, and duplicated descriptions are omitted. In addition, in the drawings, the configuration may be omitted or simplified for convenience of description. In addition, at least a part of each embodiment and each modified example may be arbitrarily combined with each other. In addition, when it is necessary to explain each of the components individually because of differences in the formation locations, for example, different reference numerals are given to each of the light emitting units EM11, EM12, EM13, etc., but when explaining the functions that the components originally have, it may be expressed as, for example, the light emitting unit EM.

[0016] [Configuration of a semiconductor laser device according to a preferred embodiment] FIG. 1 is a perspective view of a main part showing an example of the configuration of a semiconductor laser device according to a preferred embodiment.

[0017] In addition, regarding the x-axis, y-axis, and z-axis shown in Fig. 1, x means the horizontal direction / width direction / lateral direction, y means the resonator direction / depth direction / vertical direction, and z means the vertical direction / thickness direction / height direction. The definitions of these directions are the same in other figures.

[0018] 1, in the semiconductor laser device LD0 according to the preferred embodiment, an n-type cladding layer 2, an emission layer EL, and a p-type cladding layer 3 are formed on a GaAs substrate 1. At least two light emitting portions EM01 and EM02 that emit laser light are formed at a predetermined interval in the x direction. Laser light λ01 and λ02 with different wavelengths are emitted from the light emitting portions EM01 and EM02, respectively.

[0019] In the light emitting sections EM01 and EM02, optical waveguides OW01 and OW02 constituted by a light emitting layer EL and a part of the first cladding layer 2 and the second cladding layer 3 are formed in the cavity direction (y direction), respectively.

[0020] Further, at least on the light emitting end surface side of the optical waveguide OW, an adjustment region AR for adjusting (correcting) the beam shape of the laser light λ01, λ02 emitted from the first and second light emitting units EM01, EM02 is provided. The adjustment region AR includes a first adjustment region AR01 formed in the first light emitting unit EM01 and a second adjustment region AR02 formed in the second light emitting unit EM02. The first and second adjustment regions AR01, AR02 may be formed at least in the light emitting layers EL01, EL02 of the optical waveguides OW01, OW02. The lengths ARL01, ARL02 of the first and second adjustment regions AR01, AR02 in the resonator direction are formed differently. Note that, although the adjustment region AR is formed within the region of the light emitting unit EM in the x direction in FIG. 1, the formation range in the x direction is not particularly limited thereto and can be formed in any range that produces an effect.

[0021] In this way, by making the lengths of the first and second adjustment regions AR01 and AR02 in the resonator direction different, the difference in the beam shapes of the laser beams λ01 and λ02 caused by the different wavelengths can be corrected, and the variation in the beam shapes can be suppressed.

[0022] The adjustment region AR for adjusting (correcting) the beam shape of the laser light means a region where the degree of light confinement is relatively weak, and is a region where the difference in refractive index between the first cladding layer 2, the second cladding layer 3, and the light emitting layer EL constituting the optical waveguide is small. As an example, it is a region selected from the following. (1) A region in the light-emitting layer EL where the band gap energy of the light-emitting layer EL in a specific region is wider than that of the light-emitting layer EL in other regions. (2) A region in the light-emitting layer EL where the band gap energy of the light-emitting layer EL in a specific region is closer to that of the cladding layers 2 and 3. (3) A region in the optical waveguide where the equivalent refractive index of the optical waveguide OW in a specific region is relatively lower than that of the waveguide OW in other regions. (4) A region in the light-emitting layer EL where the thickness of the light-emitting layer EL in a specific region is relatively thinner than that of the light-emitting layer EL in other regions. (5) A region in the light-emitting layer EL where the composition of the light-emitting layer EL in a specific region is made different from that of the light-emitting layer EL in other regions so as to widen the band gap energy or reduce the equivalent refractive index. An example of a different composition is whether or not a large amount of zinc (Zn) is mixed in as an impurity compared to other regions. (6) A region where the above-mentioned (1) to (5) are appropriately combined.

[0023] [Embodiment 1] In the semiconductor laser device LD1 according to the first embodiment, three light emitting parts EM11, EM12, and EM13 that emit laser light are formed, and the light emitting parts EM emit laser light λ11, λ12, and λ13 with different wavelengths. In the light emitting parts EM11, EM12, and EM13, optical waveguides OW11, OW12, and OW13 that are constituted by the light emitting layer EL and a part of the first cladding layer 2 and the second cladding layer 3 are formed in the resonator direction (y direction). Furthermore, in the region on the light emitting end face side of the semiconductor laser device LD1 including the optical waveguides OW11, OW12, and OW13, an adjustment region AR that adjusts (corrects) the beam shape of the laser light λ11, λ12, and λ13 emitted from the light emitting parts EM11, EM12, and EM13 is provided. The adjustment region AR includes adjustment regions AR11, AR12, and AR13 that correspond to the light emitting parts EM11, EM12, and EM13, respectively. The adjustment regions AR11, AR12, and AR13 have lengths ARL11, ARL12, and ARL13 in the resonator direction, respectively, and the lengths ARL are different from each other.

[0024] In this embodiment, the adjustment region AR is a region in which the band gap energy of the light emitting layer EL on the light emitting end face side is widened and the equivalent refractive index of the optical waveguide is made relatively small.

[0025] (Configuration of Semiconductor Laser Device) Fig. 2 is a perspective view of a main part showing an example of the configuration of the semiconductor laser device LD1 according to the embodiment 1. Fig. 3 is a top view of a main part showing the configuration of the semiconductor laser device LD1 according to the embodiment 1. Fig. 4 is a cross-sectional view of a main part showing an example of the configuration of light-emitting layers EL11-EL13 in the semiconductor laser device LD1 according to the embodiment 1.

[0026] As shown in Fig. 2, the semiconductor laser device LD1 has an n-type cladding layer 2 (thickness 2 µm), light emitting layers EL11, EL12, EL13, and a p-type cladding layer 3 (thickness 1.7 µm) formed on a GaAs substrate 1. The composition of the n-type cladding layer 2 and the p-type cladding layer 3 is (Al x Ga 1-x ) 1-y In y P(0 <x≦1、0<y<1)であり、ここではx=1、y=0.5とした。

[0027] The semiconductor laser device LD1 is formed with three light emitting sections EM11, EM12, and EM13, and in order to emit laser beams of different wavelengths λ, the thicknesses (ET11, ET12, ET13) of the light emitting layers EL11, EL12, and EL13 in each light emitting section EM are made different. That is, the thicknesses have the relationship ET11>ET12>ET13. In this embodiment, the respective thicknesses ET are ET11 (104 nm), ET12 (92 nm), and ET13 (80 nm). As will be described in detail later, the light emitting layers EL11, EL12, and EL13 are formed by selective growth, so that the respective thicknesses ET can be made different.

[0028] The wavelengths λ emitted from the three light-emitting sections EM11, EM12, and EM13 have the following relationship: light-emitting section EM11>light-emitting section EM12>light-emitting section EM13. As an example, the light-emitting region ER11 emits laser light with a wavelength of 642 nm (λ11), the light-emitting region ER12 emits laser light with a wavelength of 639 nm (λ12), and the light-emitting region ER13 emits laser light with a wavelength of 636 nm (λ13). In this way, the wavelength of the laser light varies depending on the thickness ET of the light-emitting layer EL, and the thicker the thickness ET of the light-emitting layer EL, the larger the value of the wavelength λ.

[0029] In the above example, the wavelengths are set with a difference of 3 nm, but the difference between these wavelengths can be appropriately selected between 1 nm and 30 nm. For example, when the difference in wavelength is 1 nm, the light emitting region ER11 emits laser light with a wavelength of 622 nm, the light emitting region ER12 emits laser light with a wavelength of 621 nm, and the light emitting region ER13 emits laser light with a wavelength of 620 nm. When the difference in wavelength is 30 nm, the light emitting region ER11 emits laser light with a wavelength of 690 nm, the light emitting region ER12 emits laser light with a wavelength of 660 nm, and the light emitting region ER13 emits laser light with a wavelength of 630 nm.

[0030] In each of the light emitting sections EM11, EM12, EM13, a ridge groove RG is formed by etching a part of the p-type cladding layer 3, and ridges R11, R12, R13 are formed as a current confinement structure (current injection structure) and a structure for lateral light confinement (x direction). In this way, the ridge R has a ridge structure formed along the resonator direction (y direction) so that it is sandwiched on both sides by air (refractive index = 1) which has a lower refractive index than the p-type cladding layer 3.

[0031] In the light emitting sections EM11, EM12, and EM13, optical waveguides OW11, OW12, and OW13 constituted by a light emitting layer EL and a part of the first cladding layer 2 and the second cladding layer 3 are formed in the cavity direction (y direction), respectively.

[0032] Further, an adjustment region AR that adjusts (corrects) the beam shapes of the laser beams λ11, λ12, λ13 emitted from the light emitters EM11, EM12, EM13 is provided in an area on the light emitting end face side of the semiconductor laser device LD1 including the optical waveguides OW11, OW12, OW13. That is, the adjustment region AR is formed in a part of the first cladding layer 2, the light emitting layer EL, and the second cladding layer 3 on the light emitting end face side.

[0033] The adjustment region AR is a region in which the band gap energy of the light emitting layer EL on the light emitting end face side is widened and the equivalent refractive index of the optical waveguide is relatively small. In the present embodiment, as an example, it is a region in which zinc (Zn) is mixed by a method such as thermal diffusion. By mixing zinc (Zn), the light emitting layer EL and the clad layers 2 and 3 are mixed, and the band gap energy of the light emitting layer EL is widened. As a result, the refractive index of the light emitting layer EL is reduced, and the equivalent refractive index of the optical waveguide is lowered. Although the details will be described later, the region with a small equivalent refractive index has a small degree of light confinement, and can act in a direction to widen the beam shape of the laser light in the optical waveguide.

[0034] In the semiconductor laser device LD1 according to this embodiment, the adjustment region AR is formed continuously in the x direction on the light emitting end face, but has different lengths in the resonator direction (y direction). That is, the adjustment region AR includes adjustment regions AR11, AR12, and AR13 corresponding to the light emitting portions EM11, EM12, and EM13, respectively. The adjustment regions AR11, AR12, and AR13 have lengths ARL11, ARL12, and ARL13 in the resonator direction, and the lengths ARL are different. In this embodiment, as an example, the lengths ARL are ARL11 (20 μm), ARL12 (15 μm), and ARL13 (10 μm).

[0035] 2 and 3, in the semiconductor laser device LD1 according to this embodiment, a rear region ARR having a configuration similar to that of the adjustment region AR is also formed on the light reflecting end face side. In the plan views (a) of FIGS. 2 and 3, the rear region ARR is formed continuously over the x direction on the light reflecting end face, and the length of the rear region ARR in the resonator direction is the same. Note that, from the viewpoint of suppressing the variation in the beam shape of the laser light, it is not necessarily required to form the rear region ARR, but it may be formed for other reasons (described later in the fourth embodiment), from the viewpoint of end face protection, or for convenience in manufacturing.

[0036] As a modification of the rear region ARR, as shown in the plan view (b) of Fig. 3, the rear region ARR formed on the light reflecting end face side may be made similar in shape to the adjustment region AR formed on the light emitting end face side. That is, the lengths ARL11 and ARRL111 of the adjustment region AR11 and the rear region ARR111 in the resonator direction in the light emitting unit EM11 are formed to be the same. Similarly, the lengths ARL12 and ARRL121 of the adjustment region AR12 and the rear region ARR121 ​​in the resonator direction in the light emitting unit EM12 are formed to be the same. Also, the lengths ARL13 and ARRL131 of the adjustment region AR13 and the rear region ARR131 in the resonator direction in the light emitting unit EM13 are formed to be the same.

[0037] When the thickness of the light-emitting layer EL is large, the degree of light confinement increases, and the light density at the end face becomes high. For example, the thickness of the light-emitting layer EL11 is formed to be thicker than the thicknesses of the other light-emitting layers EL12 and EL13. Therefore, by making the rear region ARR111 formed on the light-reflecting end face side of the thick light-emitting layer EL11 longer, it is possible to further improve protection of the rear end face (light-reflecting end face). Furthermore, an n-side electrode and a p-side electrode (not shown) are formed on the back surface of the GaAs substrate 1 and the upper surface of the ridge R. When a current is applied to the n-side electrode and the p-side electrode, laser light (wavelength: 600 nm to 700 nm) in the red region is emitted from light emitting regions ER11, ER12, and ER13 formed in the three light emitting units EM11, EM12, and EM13.

[0038] The configuration of the light-emitting layers EL11, EL12, and EL13 will be described with reference to FIG. 4. The light-emitting layer EL functions as a core layer as an optical waveguide. As shown in FIG. 4, the light-emitting layer EL is composed of, from the bottom, a lower n-side guide layer nGL, a barrier layer BL, a quantum well layer QW, a barrier layer BL, and an upper p-side guide layer pGL. The thickness of the light-emitting layer EL depends on the wavelength and the refractive index of each layer, but is selected from the range of about 50 nm to about 500 nm for red lasers, and is about 100 nm in this embodiment. The light-emitting regions ER11, ER12, and ER13 shown in FIG. 2 mainly correspond to desired regions of the quantum well layer QW. In FIG. 4, the quantum well layer QW is shown as a single quantum well layer (SQW), but may be a multiple quantum well layer (MQW).

[0039] In the semiconductor laser device LD1 according to this embodiment, the thicknesses of the layers constituting the light-emitting layer EL are set as follows. The light-emitting layer EL11 is composed of, from the bottom, a lower n-side guide layer nGL (40 nm), a barrier layer BL (9 nm), a quantum well layer QW (6 nm), a barrier layer BL (9 nm), and an upper p-side guide layer pGL (40 nm), and the total thickness ET11 is 104 nm. The light-emitting layer EL12 is composed of, from the bottom, a lower n-side guide layer nGL (35 nm), a barrier layer BL (8.25 nm), a quantum well layer QW (5.5 nm), a barrier layer BL (8.25 nm), and an upper p-side guide layer pGL (35 nm), and the total thickness ET12 is 92 nm. The light-emitting layer EL13 is composed of, from the bottom up, a lower n-side guide layer nGL (30 nm), a barrier layer BL (7.5 nm), a quantum well layer QW (5 nm), a barrier layer BL (7.5 nm) and an upper p-side guide layer pGL (30 nm), and has a total thickness ET13 of 80 nm.

[0040] Thus, the thicknesses ET of the light-emitting layers EL are ET11 (104 nm), ET12 (92 nm), and ET13 (80 nm), and the thicknesses vary in increments of 12 nm.

[0041] The crystalline layers of the light-emitting layers EL11, EL12, and EL13 are (Al x Ga1-x ) 1-y In y It is composed of a crystal layer of P(0≦x<1, 0<y<1). The quantum well layer QW is (Ga 1-y In y P(x = 0, y = 0.55), and the guide layer GL and the barrier layer BL are (Al x Ga 1-x ) 1-y In y P(x = 0.7, y = 0.5). In the quantum well layer QW, the Al composition (x) is set to x = 0, but the Al composition (x) in the light-emitting layer EL can be appropriately selected so that it is the smallest in the quantum well layer QW. However, when the Al composition (x) of the quantum well layer QW becomes larger than about 0.5, it becomes an indirect transition type. Therefore, the Al composition (x) of the quantum well layer QW is preferably 0.5 or less.

[0042] Also, in the semiconductor laser device according to this embodiment, by changing the thickness ET of the light-emitting layer EL, it is possible to emit laser light of different wavelengths from one chip. However, even without changing the thickness of the light-emitting layer EL, by changing the composition ratio of, in particular, In (indium) among the compositions constituting the crystal layer of the light-emitting layer EL, the energy bandgap can be changed, and it is also possible to emit a plurality of laser lights of different wavelengths from one chip. In this case, as an example, if the In composition ratio (y) of the light-emitting layer EL11 is 0.59, the In composition ratio (y) of the light-emitting layer EL12 is 0.55, and the In composition ratio (y) of the light-emitting layer EL13 is 0.51, it is possible to emit laser light of different wavelengths from one chip. Note that this In composition ratio (y) is preferably selected from the range of 0.35 to 0.65.

[0043] Note that when referring to the light-emitting layer EL in this embodiment, it means including all of the above-mentioned lower n-side guide layer nGL, quantum well layer QW, barrier layer BL, and upper p-side guide layer pGL in the light-emitting layer EL. In addition, it may mean including the quantum well layer QW and the barrier layer BL, or may also mean including at least a part of either one of the p-type clad layer 3 and the n-type clad layer 2.

[0044] Moreover, unless otherwise specified, the configuration of the light-emitting layer EL shown in FIG. 4 is the same as that of the light-emitting layer EL in other embodiments described later.

[0045] (Laser light beam shape (NFP / FFP)) Next, the near field pattern (NFP) and far field pattern (FFP) used to evaluate the beam shape and characteristics of laser light will be described with reference to Fig. 5 and Fig. 6. Note that the NFP and FFP have shapes in the horizontal direction (slow axis) corresponding to the x direction and the vertical direction (fast axis) corresponding to the z direction. In evaluating the characteristics of the beam shape, evaluation and consideration are required in both the horizontal and vertical directions, but in this embodiment, the beam shape in the vertical direction will be described unless otherwise specified.

[0046] First, the definitions of NFP and FFP will be described with reference to Fig. 5. In Fig. 5, (a) is a schematic side view of the light-emitting end face of a semiconductor laser device, (b) is a schematic top view of the semiconductor laser device as seen from above, and (c) and (d) are diagrams showing distribution examples indicating NFP and FFP, respectively.

[0047] As shown in (b), the laser light propagates through the optical waveguide OW and is emitted from the light output surface to the outside. NFP indicates the characteristics of the beam shape at the light output surface, and as shown in (c), the horizontal axis is expressed as the vertical position (μm) corresponding to the z direction, and the vertical axis is expressed as the light intensity. FFP indicates the characteristics of the beam shape at a position (approximately 10 mm) away from the light output surface, and as shown in (d), the horizontal axis is expressed as the angle (deg) indicating the beam spread angle in the z direction, and the vertical axis is expressed as the light intensity. In other words, when it comes to the beam shape of laser light, it is important to evaluate the beam shape after it is emitted from the light output surface that is directly visible to humans, that is, the beam shape indicated by FFP.

[0048] FIG. 6 is an explanatory diagram showing the relationship between NFP and FFP. In FIG. 6, the solid line shows the characteristics when the wavelength λ is long, and the dashed line shows the characteristics when the wavelength λ is short. In the case of laser light with a narrow vertical beam shape in NFP, the vertical beam spread angle is wider in FFP. On the other hand, in the case of laser light with a wide vertical beam shape in NFP, the vertical beam spread angle is narrower in FFP. This can be explained by the wave diffraction phenomenon, but the explanation will be omitted here. Thus, it can be said that it is necessary to improve the beam characteristics in NFP in order to adjust the beam spread angle in FFP.

[0049] Here, the laser light propagates through the optical waveguide and is emitted to the outside. The optical waveguide is composed of the ridge R (part of the p-type cladding 3), the light emitting layer EL, and part of the n-type cladding 2. As described above, the semiconductor laser device LD1 according to this embodiment employs a ridge structure, and therefore, the ridge R is surrounded by SiO 2 There are media with low refractive index such as air.

[0050] The beam shape of laser light varies depending on the equivalent refractive index weighted by the light distribution (i.e., the equivalent refractive index felt by the light). The light distribution includes three elements: the refractive index of the material through which the laser light passes, the film thickness, and the wavelength (the wavelength of light in a vacuum). For example, when the wavelength λ of the laser light changes, the equivalent refractive index felt by the light propagating in the optical waveguide changes, and as a result, the beam shape (NFP) of the laser light changes. Similarly, when the film thickness of the light-emitting layer EL increases, the equivalent refractive index felt by the light propagating in the optical waveguide increases, and as a result, the beam shape (NFP) of the laser light changes.

[0051] In the structure of this embodiment, when the equivalent refractive index increases due to the increase in the thickness of the light-emitting layer EL, the degree of light confinement in the optical waveguide becomes relatively stronger, and the beam shape (NFP) of the laser light becomes narrower. In other words, the beam shape of the laser light with a long wavelength becomes relatively narrower than the beam shape of the laser light with a short wavelength.

[0052] Therefore, when emitting multiple laser beams with different wavelengths, in order to align the beam divergence angle (FFP), it is important to consider the laser beam's beam shape (NFP) as it propagates through the optical waveguide. In this way, by controlling the equivalent refractive index of each optical waveguide of laser beams with different wavelengths, it is possible to adjust (correct) the beam shape of each laser beam, and as a result, it is possible to suppress the difference in the beam shape of each emitted laser beam.

[0053] (Improved beam shape) Next, the improvement results of NFP and FFP by forming the adjustment region AR will be described. Fig. 7A is an explanatory diagram showing the improvement results of the beam shape (NFP) of the laser light in the semiconductor laser device LD1 according to the present embodiment 1. Fig. 7B is a graph showing the improvement results of the beam shape (NFP) of the laser light in the semiconductor laser device LD1 according to the present embodiment 1. Fig. 7C is a graph showing the improvement results of the beam shape (FFP) of the laser light in the semiconductor laser device LD1 according to the present embodiment 1. In FIG. 7A, (A) is a diagram showing a schematic diagram of the process in which the laser beams λ11 to λ13 in the light emitting units EM11 to EM13 propagate through the optical waveguide. The right side is the direction of the light emitting end face on the front side, and the left side is the direction of the light reflecting end face on the rear side. In addition, in the figure, the vertical beam shape (NFP) at each position ((a) to (e)) in the optical waveguide is shown. The dotted line (P) is the boundary between the adjustment region AR and the gain region (also called the non-adjusted region non-AR) formed in the optical waveguide, and the right side of the dotted line (P) is the adjustment region AR, and the left side is the gain region (non-adjusted region non-AR). In addition, in FIG. 7A, (B) is a graph showing qualitatively the degree of spread of the beam shape (NFP) in the vertical direction of the laser beams λ11 to λ13 as they propagate through the optical waveguide. The horizontal axis indicates the propagation length (μm), and the vertical axis indicates the full width at half maximum of the vertical beam shape (NFP). As mentioned above, the wavelengths of the laser beams are λ11 (642 nm), λ12 (639 nm), and λ13 (636 nm).

[0054] As shown in FIG. 7A (A), at position (a) in the optical waveguide, the beam shapes of the laser beams λ11, λ12, and λ13 are different. This is because the quantum well of EM11 is thick and the degree of optical confinement is relatively strong, so the vertical beam shape (NFP) is narrow and the NFP value is small. In addition, in EM13, the quantum well is thin and the degree of optical confinement is relatively weak and the equivalent refractive index in the optical waveguide is relatively low. Therefore, the vertical beam shape (NFP) spreads and the NFP value increases. The vertical NFP at position (a) varies greatly, as shown in FIG. 7A (B) near the propagation length of 0 μm. If the adjustment region AR is not provided, each laser beam will be emitted from the light emitting end face with the beam shape at position (a), resulting in laser beams with uneven spread angles of the vertical beam shape (FFP).

[0055] In this embodiment, an adjustment area AR is provided to adjust (correct) the vertical beam shape (NFP) of each laser light. The adjustment area AR is formed up to a position 20 μm (ARL11) from the light output end face in EM11, 15 μm (ARL12) from the light output end face in EM12, and 10 μm (ARL13) from the light output end face in EM13.

[0056] Here, as described above, the adjustment region AR is a region in which the band gap energy of the light emitting layer EL on the light emitting end surface side is widened and the equivalent refractive index of the optical waveguide is relatively small. Therefore, in the laser light λ11 having a narrow vertical beam shape (NFP), the vertical beam shape (NFP) can be corrected in the widening direction by propagating the laser light λ11 through an optical waveguide with a relatively small equivalent refractive index over a long distance. As shown in FIG. 7A, the beam shape of the laser light λ11 in EM11 can be widened from position (a) to position (e). In addition, in the laser light λ13 having a wide vertical beam shape (NFP), the widening width of the vertical beam shape (NFP) can be reduced by propagating the laser light λ13 through an optical waveguide with a relatively small equivalent refractive index over a short distance.

[0057] In this way, by adjusting the length ARL of the adjustment region AR in the resonator direction for each light emitting portion EM, it is possible to suppress the variation in the vertical beam shape (NFP) in the vicinity of the propagation length of 20 μm (light emitting end face) corresponding to position (e), as shown in (B). Therefore, by adjusting the propagation distance in the adjustment region AR according to the beam shape of each laser light (i.e., according to the wavelength of the laser light), it is possible to align the spread angle of the beam shape (FFP) of the laser light emitted from the light emitting end face.

[0058] 7B and 7C show the results of improving the beam shape (NEP, FFP) of the laser light. In each figure, (a) shows the NFP characteristic and the FFP characteristic when the adjustment region AR is not formed as a comparative example. (b) shows the NFP characteristic and the FFP characteristic in the semiconductor laser device LD1 according to the first embodiment. The solid line shows the NFP characteristic and the FFP characteristic corresponding to the light emitting unit EM13 (wavelength λ13=636 nm), and the dotted line shows the NFP characteristic and the FFP characteristic corresponding to the light emitting unit EM11 (wavelength λ=642 nm). Note that, for the sake of comparison, the NFP characteristic and the FFP characteristic of the light emitting unit EM12 (wavelength λ12=639 nm) that emits an intermediate wavelength are omitted in FIG. 7B and FIG. 7C.

[0059] 7B, in the comparative example (a), the difference in the full width at half maximum of the NFP was 0.15 μm, but in the semiconductor laser device LD1 according to the first embodiment (b), the difference in the full width at half maximum of the NFP could be reduced to 0.03 μm. In this way, the variation in the characteristics of the NFP shape in the vertical direction is improved.

[0060] 7C, in the comparative example (a), the difference in the FWHM of the FFP was 1.9°, but in the semiconductor laser device LD1 according to the first embodiment (b), the difference in the FWHM of the NFP could be reduced to 0.3°. In this way, the variation in the characteristics of the FFP shape in the vertical direction is improved.

[0061] In this way, by making the length ARL of the adjustment region AR in the resonator direction different for each light-emitting section EM, the NFP of the laser light propagating within the optical waveguide is improved, and as a result, the FFP (spread angle of the beam shape) is improved, making it possible to suppress the variation in the vertical spread angle of each beam shape.

[0062] The degree of difference in the divergence angle of the beam shape of the multiple laser beams depends on the design of the semiconductor laser device, but (Al x Ga 1-x ) 1-y In y Compared to GaN-based blue lasers, P-based red lasers have a larger refractive index difference between the light emitting layer and the cladding layer, so there is a tendency for the influence of differences in structure such as film thickness to be greater. Therefore, the method of adjusting the equivalent refractive index in the optical waveguide as in this embodiment has a more significant effect when applied to red lasers.

[0063] (Relationship between beam shape adjustment area AR and window structure) As the output of semiconductor laser devices increases, catastrophic optical damage (COD) occurs, and as a countermeasure, a method called an end face window structure that reduces the optical absorption of the light emitting end face is known. Next, the relationship between the adjustment area AR and the window structure in this embodiment will be described.

[0064] The window structure is a technology that aims to reduce heat generation near the light-emitting end face by expanding the band gap energy near the light-emitting end face and suppressing light absorption. Such a window structure is formed by diffusing impurities into the light-emitting end face and intermixing the cladding layer with the light-emitting layer and the guide layer.

[0065] The adjustment region AR in this embodiment is a region for eliminating the difference in refractive index between the entire light-emitting layer EL and the clad layers 2 and 3. As described above, the light-emitting layer EL is composed of the quantum well layer QW, the barrier layer BL, and the guide layer GL, and even if the refractive index of at least the guide layer GL is reduced, it has the effect of adjusting (correcting) the beam shape.

[0066] On the other hand, the minimum requirement for a window structure to counter COD is that the band gap energy of the quantum well layer must be wide. Even if the band gap energy of the guide layer or barrier layer changes, if the band gap energy of the quantum well layer does not change, there will be almost no effect as a COD countermeasure.

[0067] Moreover, the adjustment region AR in this embodiment is a region where the band gap energy is expanded. As an example of the adjustment region AR, when the band gap wavelength is 10 nm shorter than the emission wavelength, it is insufficient as a window structure for COD countermeasures, but can be considered as a region that has the effect of changing the beam shape. For example, in the case of a light emitting section with an emission wavelength of 630 nm, if the band gap wavelength of the light emitting layer or the guide layer in the vicinity of the region near the light emitting end face is 620 nm or less, the effect of widening the beam shape can be obtained. On the other hand, a region (gain region) where a current is injected and light is emitted, or a region where the band gap wavelength does not change even if no current is injected is not the adjustment region AR in this embodiment, but a non-adjustment region. Note that, as an example of a method for confirming the band gap wavelength of the adjustment region AR, there is photoluminescence measurement. This is a method of measuring light generated in the process of a material in an excited state relaxing to a stable state by applying light having energy higher than the band gap energy from the outer surface. When the photoluminescence wavelength near the end face is 10 nm or more shorter than the emission wavelength, or when the photoluminescence intensity decreases due to progress in intermixing, it can be assumed that the device has the characteristics of the adjustment region AR in this embodiment.

[0068] (Method of manufacturing a semiconductor laser device) Next, a description will be given of an example of a method for manufacturing the semiconductor laser device LD1 according to the first embodiment. Figures 8 to 13 are cross-sectional views of a main part showing an example of steps included in the method for manufacturing the semiconductor laser device LD1.

[0069] The manufacturing method of the semiconductor laser device LD1 according to Embodiment 1 mainly includes: (1) a step of forming an n-type clad layer 2 on a GaAs substrate 1; (2) a step of forming a mask MK; (3) a step of selectively growing light-emitting layers EL11, EL12, and EL13; (4) a step of forming a p-type clad layer 3 and a cap layer 4 (including the step of removing the mask MK); (5) a step of forming an adjustment region AR; and (6) a step of forming a ridge R and electrodes and separating them into individual chips.

[0070] (1) A step of forming an n-type clad layer 2 on a GaAs substrate 1 First, as shown in FIG. 8, an n-type clad layer 2 with a thickness of about 2 μm is epitaxially grown on the GaAs substrate 1 by the MOCVD method. The source gases used are trimethylaluminum (TMA), trimethylgallium (TMG), trimethylindium (TMI), etc. The composition of the n-type clad layer 2 is (Al x Ga 1-x ) 1-y In y P (0 < x ≦ 1, 0 < y < 1), and here x = 1 and y = 0.5. In this embodiment, considering the lattice matching with the GaAs substrate 1, the In composition y is adjusted to 0.5. Also, the composition ratio of Al to Ga (x: 1 - x) is preferably such that x is larger, and (x: 1 - x) = 1: 0 is also acceptable.

[0071] (2) A step of forming a mask MK Next, after forming the n-type clad layer 2, a silicon oxide (SiO 2 ) film that functions as a mask MK is formed on the surface of the n-type clad layer 2 by the CVD method. This SiO 2 film is a film that inhibits crystal growth, and for example, a silicon nitride (Si 3 N 4 ) film may be used.

[0072] After forming the SiO 2 film, as shown in FIG. 9, using the lithography method, SiO 2A plurality of stripe-shaped openings (three openings in this embodiment) are formed in the film. The widths of the three openings (corresponding to the size in the x-direction (horizontal direction)) are different from each other, and they are formed so as to become wider in order from the left side of FIG. 9. That is, as an example, the widths of the openings are EW11 (20 μm), EW12 (30 μm), and EW13 (40 μm). Also, as an example, the respective mask widths are MK1 (50 μm), MK2 (25 μm), MK3 (15 μm), and MK4 (5 μm).

[0073] (3) Step of forming light-emitting layers EL11, EL12, and EL13 by selective growth method Next, as shown in FIG. 10, in the region of the opening of the mask MK, light-emitting layers EL11, EL12, and EL13 composed of a lower n-side guide layer nGL, a barrier layer BL, a quantum well layer QW, a barrier layer BL, and an upper p-side guide layer pGL are formed. The formation of these layers is carried out by a method called selective growth. The selective growth method utilizes the fact that no crystal is deposited on the upper surface of the mask MK, and forms a desired film only in the region of the opening of the mask MK.

[0074] The crystal grown by the selective growth method is (Al x Ga 1-x ) 1-y In y P (0 ≦ x <1, 0 <y <1), and the source gases used are trimethylaluminum (TMA), trimethylgallium (TMG), trimethylindium (TMI), etc.

[0075] By selective growth, the lower n-side guide layer nGL, the barrier layer BL, the quantum well layer QW, the barrier layer BL, and the upper p-side guide layer pGL are formed in the order shown in FIG. 4 in each region of the opening of the mask MK. In the region (EW11) of the mask MK shown in FIG. 9 where the opening is the narrowest, the light-emitting layer EL11 is formed as shown in FIG. 10, and in the region (EW13) of the mask MK where the opening is the widest, the light-emitting layer EL13 is formed. When the light-emitting layer EL is formed by selective growth, a gentle slope is formed on the side of the light-emitting layer EL, but this is omitted in the drawing. Also, FIG. 4 shows the case of a single quantum well layer QW, but a multiple quantum well layer having multiple quantum wells may be used.

[0076] In the process of forming the light-emitting layer EL, (Al x Ga 1-x ) 1-y In y P is formed by selective growth, and the values ​​of x and y, which indicate the composition ratio of each element, are set as follows. That is, in this embodiment, the guide layer GL and the barrier layer BL have x=0.7 and y=0.5. In addition, the quantum well layer QW is formed of GaInP that does not contain Al (i.e., x=0) without supplying TMA as a source gas during growth.

[0077] The guide layer GL is sometimes called an SCH (Separated Confinement Heterostructure) layer or confinement layer, and preferably has a higher refractive index than the cladding layer 2(3) and a lower refractive index than the quantum well layer QW. Therefore, the supply ratio of the raw material is adjusted so that the Al composition ratio x is smaller than that of the cladding layer 2(3). For example, the supply amount of the raw material gas is adjusted so that the Al composition ratio x is highest in the cladding layer 2(3), and decreases in the order of the guide layer GL or barrier layer BL, and the quantum well layer QW.

[0078] As described above, the quantum well layer QW is formed to a thickness in the range of 5 nm to 6 nm. The light emitting layer EL formed by the selective growth method functions as a core layer as an optical waveguide. The thickness of the light emitting layer EL depends on the wavelength and the refractive index of each layer, but is selected from the range of about 50 nm to about 500 nm for red lasers, and in this embodiment, the total thickness is about 100 nm.

[0079] In addition, the thickness ET of the light-emitting layer EL formed by the selective growth method is different for each light-emitting layer EL. That is, the thickness of the selectively grown light-emitting layer EL differs depending on the size of the opening of the mask MK, and the narrower the width EW of the light-emitting layer EL, the thicker the thickness ET of the light-emitting layer EL. Specifically, the thicknesses ET have the following relationship (see FIG. 2): ET11 (104 nm)>ET12 (92 nm)>ET13 (80 nm).

[0080] As described above, when the light-emitting layer EL is deposited in different opening regions of the mask MK by selective growth, the film thickness of the light-emitting layer EL differs. Although the mechanism behind this is not clear, it can be assumed that the following reasons (i) to (iv) are involved.

[0081] (i) In the selective growth method, since no film growth occurs on the surface of the mask MK, the source gas supplied to the surface of the mask MK migrates over the surface of the mask MK and moves to the opening region of the mask MK. (ii) The larger the surface area of ​​the mask MK, the greater the amount of source gas that moves. (iii) In the opening region of the mask MK adjacent to the mask MK with a large surface area, a larger amount of source gas moves to the opening, and the concentration of the source gas at the opening becomes higher. Also, if the opening of the mask MK is smaller, the concentration of the source gas becomes higher. (iv) As a result, a larger amount of source gas is supplied to the light-emitting layer EL11 formed in the region where the opening of the mask MK is narrowest.

[0082] Note that, not limited to the above embodiment, a part of the lower n-side guide layer nGL may be formed continuously on the n-type cladding layer 2 before the formation of the mask MK. Alternatively, after forming an opening in the mask MK, a part of the n-type cladding layer 2 may be selectively grown, and then the lower n-side guide layer nGL may be selectively grown. Further, after the formation of the upper p-side guide layer pGL, a part of the p-type cladding layer 3 formed in the next step (4) may be selectively grown.

[0083] (4) Step of forming the p-type cladding layer 3 and the cap layer 4 (including the step of removing the mask MK) Next, as shown in FIG. 11, the mask MK is removed. Then, as shown in FIG. 12, a p-type cladding layer 3 having a thickness of about 1.7 μm is epitaxially grown by the MOCVD method, and the source gases used are trimethylaluminum (TMA), trimethylgallium (TMG), trimethylindium (TMI), etc. The composition of the p-type cladding layer 3 is (Al x Ga 1-x ) 1-y In y P (0 <x ≦ 1, 0 <y <1), and here x = 1, y = 0.5. Subsequently, GaAs is formed as a 300 nm cap layer 4 on the upper surface of the p-type cladding layer 3.

[0084] Note that, during the formation of the p-type cladding layer 3, a step of forming an etch stop layer (not shown) may be included. The etch stop layer functions as an etching stop layer when etching the p-type cladding layer 3 to form the ridge R in the subsequent step (6).

[0085] (5) Step of forming the adjustment region AR Next, as shown in FIG. 13, a silicon oxide (SiO 2 ) film that functions as a mask MK is formed on the surface of the cap layer 4 by the CVD method. Instead of this SiO 2 film, a material such as a silicon nitride (Si 3 N 4 ) film that can protect the semiconductor surface in the heat treatment process may be used.

[0086] After forming the mask MK, as shown in FIG. 13, an opening is formed in the mask MK by using a lithography method. This opening is formed so as to open a region corresponding to the light emitting end face. In the figure, the broken line P indicates the cleavage position of the wafer when forming the element, and is the position that becomes the resonator end face when the element is separated. Then, in this embodiment, zinc (Zn) is mixed into the p-type cladding layer 3 and the light emitting layer EL by using a method such as a thermal diffusion method or an ion implantation method at about 600° C. Alternatively, zinc (Zn) may reach the n-type cladding layer 2. The region where zinc (Zn) is mixed is a region that functions as the adjustment region AR.

[0087] At this time, by changing the size of the opening of the mask MK for each of the light-emitting portions EM11, EM12, EM13, the lengths ARL11, ARL12, ARL13 of the adjustment region AR in the resonator direction can be made different for each of the light-emitting portions EM11, EM12, EM13.

[0088] It should be noted that the vertical dashed lines P shown in FIG. 13 correspond to the locations that will be divided by cleavage during the subsequent singulation in step (6).

[0089] (6) Forming ridges and electrodes and dividing them into individual pieces Next, the p-type cladding layer 3 is etched to form the ridge groove RG shown in FIG. 2, thereby forming ridges R extending in the cavity direction for each of the light emitting layers EL11, EL12, and EL13.

[0090] Although not shown in FIG. 2 for simplicity, SiO 2 A passivation oxide film such as the above is formed, and an opening is made in the oxide film at the top of the ridge using photolithography and etching techniques, and an electrode is formed on top of it. The GaAs substrate is then cleaved, and an end face coating is formed on the cleaved surface. Through these steps, the semiconductor laser device LD1 shown in Figures 2 and 3 is formed.

[0091] Thus, in the present embodiment 1, the layer deposited by selective growth is the relatively thin light-emitting layer EL formed in step (3). On the other hand, the thick n-type cladding layer 2 and p-type cladding layer 3 formed in steps (1) and (4) are formed without using selective growth.

[0092] (effect) In the region on the light emitting end face side, an adjustment region AR for adjusting (correcting) the beam shapes of the laser beams λ11, λ12, and λ13 emitted from the light emitting parts EM11, EM12, and EM13 is provided, and the length ARL of the adjustment region AR in the resonator direction is adjusted for each light emitting part EM, thereby suppressing the variation in the vertical beam shape (NFP) of each laser beam propagating in the optical waveguide. Furthermore, it becomes possible to align the spread angle of the beam shape (FFP) of the laser beam emitted from the light emitting end face.

[0093] This enables further improvements in visibility and image quality, such as a wide color gamut, high resolution, and wide viewing angle. That is, in the first embodiment, it is possible to provide a semiconductor laser device that contributes to improvements in visibility and image quality.

[0094] [Embodiment 2] (Configuration of Semiconductor Laser Device) The semiconductor laser device LD2 according to the second embodiment has the same configuration as the semiconductor laser device LD1 according to the first embodiment, except that the concentration distribution of zinc (Zn) in the adjustment region AR2 is different. Therefore, unless otherwise specified, the following mainly describes the differences from the first embodiment, and the same description will not be repeated.

[0095] 14A and 14B are a top view and a cross-sectional view, respectively, of a main part of a semiconductor laser device LD2 according to the second embodiment. In the cross-sectional view of the main part (b), a cross-sectional view in the cavity direction (y direction) of three light-emitting layers EL21, EL22, and EL23 is shown.

[0096] In the second embodiment, as in the first embodiment, the adjustment region AR2 is a region in which the band gap energy of the light emitting layer EL on the light emitting end face side is widened and the equivalent refractive index of the optical waveguide is relatively small. That is, zinc (Zn) is mixed into the adjustment region AR2 to widen the band gap energy of the light emitting layer EL and relatively reduce the equivalent refractive index of the optical waveguide.

[0097] In this embodiment, as shown in Fig. 14, the lengths ARL21, ARL22, and ARL23 of the adjustment regions AR21, AR22, and AR23 in the resonator direction are different from each other, and the adjustment region AR2 in this embodiment has a gradient in the concentration of zinc (Zn) mixed in the adjustment region AR2. The concentration of zinc (Zn) is formed so that it gradually increases from the gain region on the light reflecting end face side toward the light emitting end face in the resonator direction. In other words, the band gap energy is gradually expanded from the gain region toward the light emitting end face. Therefore, the equivalent refractive index of the optical waveguide can be gradually reduced.

[0098] FIG. 15 is an explanatory diagram for explaining the distribution of laser light near the optical waveguide in the semiconductor laser device LD2 according to the second embodiment. In FIG. 15, the upper part shows the equivalent refractive index and zinc (Zn) concentration distribution in the resonator direction, and the lower part shows a simulation result showing the distribution of laser light. Also, (a) shows a case where there is no gradient in the zinc (Zn) concentration in the adjustment region AR, and (b) shows a case where there is a gradient in the zinc (Zn) concentration in the adjustment region AR2 according to the second embodiment. In the lower part of FIG. 15, the white region between the black regions corresponds to the region of the light emitting layer EL, and indicates that the light intensity is strong. Also, the black region corresponds to the optical waveguide OW, including a part of the cladding layers 2 and 3. In both FIG. 15(a) and (b), the right side of the figure is the light emitting end face side.

[0099] As can be seen from FIG. 15(a), when there is no gradient in the zinc (Zn) concentration and the equivalent refractive index changes sharply at the boundary of the adjustment region AR (i.e., the equivalent refractive index drops sharply), light is scattered near the boundary (dotted line portion). On the other hand, as shown in FIG. 15(b), when the zinc (Zn) concentration is gradient and the concentration is gradually increased toward the light-emitting end face, the equivalent refractive index can also be gradually decreased. As a result, the scattering of light as seen in FIG. 15(a) is suppressed, and it is possible to suppress the loss of light propagating through the optical waveguide OW. This makes it possible to increase the output efficiency of the semiconductor laser device.

[0100] (Method of manufacturing a semiconductor laser device) The concentration distribution of zinc (Zn) in the adjustment region AR2 as described above can be formed in the step (5) (FIG. 13) of forming the adjustment region AR described in embodiment 1. That is, when zinc (Zn) is diffused by a method such as thermal diffusion, the desired concentration distribution can be obtained by adjusting the temperature and time.

[0101] The other steps are similar to the manufacturing steps shown in the first embodiment, and therefore the description thereof will be omitted.

[0102] (effect) The semiconductor laser device LD2 according to the second embodiment also has the same effects as the semiconductor laser device LD1 according to the first embodiment. In the semiconductor laser device LD2 according to the second embodiment, the change rate of the equivalent refractive index in the adjustment region AR2 is gradually changed, so that it is possible to suppress the variation in the beam shape of the laser light and also to suppress the loss of the light propagating through the optical waveguide OW.

[0103] [Embodiment 3] (Configuration of Semiconductor Laser Device) The semiconductor laser device LD3 according to the third embodiment has the same configuration as the semiconductor laser device LD1 according to the first embodiment, except for the configuration of the adjustment region AR3. Therefore, unless otherwise specified, the following mainly describes the differences from the first embodiment, and the same description will not be repeated.

[0104] 16A and 16B are a top view and a cross-sectional view, respectively, of a main part of a semiconductor laser device LD3 according to the third embodiment. In the cross-sectional view of the main part (b), a cross-sectional view in the cavity direction (y direction) of three light-emitting layers EL31, EL32, and EL33 is shown.

[0105] In the adjustment region AR3 in the third embodiment, the film thicknesses Et31, Et32, and Et33 of the light-emitting layer EL in the adjustment region AR3 are made thinner than the film thicknesses ET31, ET32, and ET33 of the light-emitting layer EL in the gain region. That is, by making the film thickness Et of the light-emitting layer EL in the adjustment region AR3 thinner, the band gap energy of the light-emitting layer EL is widened and the equivalent refractive index of the optical waveguide is relatively reduced.

[0106] That is, since the thickness of the quantum well layer in the light emitting layer EL in the adjustment region AR3 is thinner than that of the quantum well layer in the gain region, the quantum level of the carriers in the quantum well layer becomes higher, and the band gap energy relatively expands. Also, since the thicknesses of the quantum well layer and the guide layer become thinner, the equivalent refractive index of the optical waveguide decreases, and the degree of optical confinement can be relatively weakened.

[0107] Also in this embodiment, as shown in FIG. 16, the lengths ARL31, ARL32, ARL33 of the adjustment regions AR31, AR32, AR33 in the resonator direction are different from one another.

[0108] It is also possible to gradually reduce the film thickness Et of the light emitting layer EL in the adjustment region AR3 toward the light reflecting end face in the resonator direction. By forming a gradient in the film thickness Et of the light emitting layer EL in the resonator direction, it is possible to suppress a steep change in the equivalent refractive index at the boundary between the adjustment region AR3 and the gain region, as described in the second embodiment. By providing a gradient in the film thickness in this way, it is possible to suppress loss due to light scattering, as in the second embodiment.

[0109] (Method of manufacturing a semiconductor laser device) The adjustment region AR3 in the third embodiment can be formed in the manufacturing process in the first embodiment, in which (2) a mask MK is formed (FIG. 9) and (3) the light-emitting layers EL11, EL12, and EL13 are formed by selective growth (FIG. 10). In addition, in the manufacturing process in the first embodiment, (5) a process of forming the adjustment region AR (FIG. 13) is omitted in the third embodiment. Unless otherwise specified, the following mainly describes the points that are different from the first embodiment, and the same description will be omitted. In addition, the other steps are the same as the manufacturing process shown in the first embodiment, and therefore the description thereof will be omitted.

[0110] (2) Step of forming a mask MK In the first embodiment, stripe-shaped openings extending in the y direction are formed in the mask MK so that openings are formed in the region where the light-emitting layer EL is formed (see FIG. 9), but in the third embodiment, continuous openings are provided in the mask MK along the x direction on both the light-emitting end face side and the light-reflecting end face side (for example, the portion of the adjustment region AR shown in FIG. 3 corresponds to the opening where the mask MK is not provided). That is, in addition to the stripe-shaped openings, large continuous openings including regions corresponding to the adjustment region AR3 and the rear region ARR3 in the x direction are provided on both the light-emitting end face side and the light-reflecting end face side.

[0111] (3) A process for forming the light-emitting layer EL by selective growth. The openings of the mask MK on the light emitting end face side and the light reflecting end face side formed in step (2) are wide openings that are continuous in the x direction. That is, the light emitting layer EL is formed as a film that is continuous in the x direction on the light emitting end face side and the light reflecting end face side. Therefore, when the light emitting layer EL is selectively grown, the film thickness Et of the light emitting layer EL in the regions corresponding to the adjustment region AR3 and the rear region ARR3 can be formed thin. The reason why different film thicknesses are formed depending on the size of the opening of the mask MK has been explained in the first embodiment, and will not be repeated here.

[0112] In this manner, the thickness Et of the light-emitting layer EL in the adjustment region AR3 can be formed thinner than the thickness ET of the light-emitting layer EL in the gain region.

[0113] In the above-described manufacturing process, the light emitting layer EL of the gain region and the light emitting layer of the adjustment region AR are formed simultaneously, but the light emitting layer EL of the gain region and the light emitting layer of the adjustment region AR may be formed separately in separate processes.

[0114] (effect) The semiconductor laser device LD3 according to the third embodiment has the same effects as those of the semiconductor laser device LD1 according to the first embodiment.

[0115] [Embodiment 4] (Configuration of Semiconductor Laser Device) The semiconductor laser device LD4 according to the fourth embodiment has the same configuration as the semiconductor laser device LD1 according to the first embodiment, except that a rear region ARR4 having a configuration similar to the adjustment region AR formed on the light emitting end face side is provided on the light reflecting end face side, and the length ARRL of the rear region ARR4 in the resonator direction is made different for each light emitting unit EM. Therefore, unless otherwise specified, the following mainly describes the points that are different from the first embodiment, and the same description will not be repeated.

[0116] Fig. 17 is a top view of a main part showing the configuration of a semiconductor laser device LD4 according to the fourth embodiment. Fig. 18 is an explanatory diagram showing the operation of the semiconductor laser device according to the fourth embodiment.

[0117] In Embodiment 4, similar to Embodiments 1, 2, and 3 described above, an adjustment region AR4 is formed on the light-emitting end face side. Note that the adjustment region AR4 can be selected from the configurations of the adjustment region AR described in Embodiments 1, 2, and 3 above. The adjustment region AR4 formed on the light-emitting end face side includes adjustment regions AR41, AR42, and AR43 formed for each light-emitting part EM. Also, the lengths ARL in the resonator direction of the adjustment regions AR41, AR42, and AR43 are different from each other, similar to the other embodiments described above, and have the relationship of ARL41 > ARL42 > ARL43.

[0118] The rear region ARR4 formed on the light-reflecting end face side includes rear regions ARR41, ARR42, and ARR43 formed for each light-emitting part EM. Also, the lengths ARRL in the resonator direction of the rear regions ARR41, ARR42, and ARR43 are different from each other and have the relationship of ARRL41 < ARRL42 < ARRL43.

[0119] Differences in the beam shape due to different wavelengths of the laser light can be adjusted (corrected) in the adjustment region AR4 formed on the light-emitting end face side, similar to the other embodiments, to suppress differences in the beam shape. However, the output characteristics of the laser light shown in FIG. 18 differ depending on the length of the gain region where the adjustment region AR is not formed. If the length of the gain region is different, variations will occur in the threshold value at which the laser light oscillates and the output efficiency.

[0120] Therefore, in this embodiment, in order to suppress the variation in the output characteristics in each light-emitting unit EM, the lengths of the gain regions are made uniform. That is, the lengths ARRL of the rear regions ARR41, ARR42, and ARR43 in the resonator direction are changed, so that the lengths of the gain regions are made uniform. In other words, the difference in the length of the gain region caused by the lengths ARL of the adjustment regions AR4 formed on the light-emitting end face side is adjusted by the rear region ARR4. Therefore, in each light-emitting unit EM, the length ARL of the adjustment region AR4 on the light-emitting end face side and the length ARRL of the rear region ARR4 on the light-reflecting end face side are formed to be different from each other.

[0121] (Method of manufacturing a semiconductor laser device) The rear region ARR41 can be formed, for example, in the step (5) (FIG. 13) of forming the adjustment region AR described in the first embodiment. That is, the rear region ARR41 can be formed by adding openings for forming the rear regions ARR41, ARR42, and ARR43 to a mask MK used when diffusing zinc (Zn) by a method such as thermal diffusion. The other steps are the same as the manufacturing steps described in the first embodiment, and therefore the description thereof will be omitted.

[0122] (effect) The semiconductor laser device LD4 according to the fourth embodiment also has the same effects as the semiconductor laser device LD1 according to the first embodiment. In the semiconductor laser device LD4 according to the fourth embodiment, the lengths ARRL of the rear regions ARR4 on the light reflecting end face side are made different for each of the light-emitting portions EM, so that the lengths of the gain regions can be made uniform for each of the light-emitting portions EM, thereby making it possible to suppress variations in output characteristics between laser light beams.

[0123] The invention made by the present inventors has been specifically described above based on the embodiments, but the present invention is not limited to the above embodiments and may be modified in various ways without departing from the gist of the invention. For example, the above embodiments have been described with respect to a semiconductor laser device in the red region, but the present invention may be applied to semiconductor laser devices in other color regions as long as the semiconductor laser device is in a visible light region other than red and can be manufactured using the same material system. In addition, the above embodiments have been described based on a ridge structure as the optical waveguide structure, but other optical waveguide structures may be used, such as a buried type, a high mesa type, a channel type, and the like. Furthermore, the respective embodiments may be appropriately combined.

[0124] Furthermore, in the above embodiment, the case has been described where three or four laser beams with different wavelengths are emitted from one semiconductor laser device, but the number of laser beams emitted may be five or more.

[0125] In addition, even if a specific numerical example is described, the numerical value may be greater than or less than the specific numerical value, unless it is theoretically clearly limited to that numerical value. In addition, the component means "B containing A as a main component," and does not exclude embodiments containing other components.

[0126] In addition, the light emitting unit EM that emits one wavelength may not be provided with the adjustment area AR, and the light emitting unit EM that emits the other wavelength may be provided with the adjustment area AR to suppress the variation in output characteristics between the beams of the laser light.

[0127] (Appendix 1) A substrate; a first clad layer of a first conductivity type and a second clad layer of a second conductivity type laminated on a main surface of the substrate; a light emitting layer formed on a first surface parallel to the main surface of the substrate, the light emitting layer being sandwiched between the first cladding layer and the second cladding layer; At least two first and second light emitting sections formed in the light emitting layer and emitting laser light; an optical waveguide including the light emitting layer, the first cladding layer, and a part of the second cladding layer, the optical waveguide extending in a resonator direction; an adjustment region that adjusts the beam shape of the laser light emitted from the first and second light-emitting units; the adjustment region is formed at least on the light emitting end surface side of the optical waveguide, and includes a first adjustment region formed in the first light emitting portion and a second adjustment region formed in the second light emitting portion, the first and second adjustment regions being formed in the light emitting layer corresponding at least to the first and second light emitting portions, respectively; a first wavelength of the first laser light emitted from the first light-emitting unit is different from a second wavelength of the second laser light emitted from the second light-emitting unit; A semiconductor laser device, wherein the first and second adjustment regions have different lengths in the resonator direction.

[0128] (Appendix 2) 2. The semiconductor laser device according to claim 1, the first wavelength is longer than the second wavelength; A semiconductor laser device, wherein the length of the first adjustment region in the resonator direction is longer than the length of the second adjustment region in the resonator direction.

[0129] (Appendix 3) 2. The semiconductor laser device according to claim 1, A semiconductor laser device, wherein the band gap energy of each of the first and second adjustment regions is wider than the band gap energy of each of the light emitting layers located at a central portion in the cavity direction.

[0130] (Appendix 4) 2. The semiconductor laser device according to claim 1, A semiconductor laser device, wherein the equivalent refractive index of each of the first and second adjustment regions is lower than the equivalent refractive index in each of the waveguides located at the center in the resonator direction.

[0131] (Appendix 5) 2. The semiconductor laser device according to claim 1, A semiconductor laser device, wherein the thicknesses of the light-emitting layers in the first and second adjustment regions are different from the thicknesses of the light-emitting layers located in a central portion in the resonator direction.

[0132] (Appendix 6) 6. The semiconductor laser device according to claim 5, a thickness of each of the light-emitting layers in the first and second adjustment regions is thinner than a thickness of each of the light-emitting layers located in a central portion in the resonator direction.

[0133] (Appendix 7) 2. The semiconductor laser device according to claim 1, A semiconductor laser device, wherein the composition of each of the light-emitting layers in the first and second adjustment regions is different from the composition of each of the light-emitting layers located in a central portion in the cavity direction.

[0134] (Appendix 8) 8. The semiconductor laser device according to claim 7, The first and second adjustment regions are regions in which zinc (Zn) is mixed at a higher concentration than the central portion in the resonator direction, The concentration of the zinc is gradually decreased from the light emitting end face toward the resonator.

[0135] (Appendix 9) 2. The semiconductor laser device according to claim 1, a light reflecting end face formed on the opposite side of the light emitting end face in the resonator direction, and on the light reflecting end face side, regions having the same configuration as the first and second adjustment regions are formed with different lengths in the resonator direction.

[0136] (Appendix 10) 2. The semiconductor laser device according to claim 1, A semiconductor laser device, wherein the length in the resonator direction of the gain region disposed at the center of the waveguide is the same in the first and second light emitting portions.

[0137] (Appendix 11) In the semiconductor laser device according to Appendix 1, the light emitting layer is composed of a crystal layer of (Al x Ga 1-x ) 1-y In y P (0 ≦ x < 1, 0 < y < 1), and the laser light is laser light in the red region.

Explanation of symbols

[0138] AR Beam shape adjustment region Length in the resonator direction of the ARL adjustment region ARR Rear region Length in the resonator direction of the ARRL rear region BL Barrier layer EM Light emitting portion EL Light emitting layer ER Light emitting region EW Width of the light emitting layer ET Thickness of the light emitting layer OW Optical waveguide region R Ridge LD Semiconductor laser device QW Quantum well layer MK Mask nGL Lower n-side guide layer pGL Upper p-side guide layer 1 GaAs substrate 2 n-type cladding layer 3 p-type cladding layer 4 Cap layer

Claims

1. A substrate; a first clad layer of a first conductivity type and a second clad layer of a second conductivity type laminated on a main surface of the substrate; a light emitting layer formed on a first surface parallel to the main surface of the substrate, the light emitting layer being sandwiched between the first cladding layer and the second cladding layer; At least two light emitting sections, a first light emitting section and a second light emitting section, are formed in the light emitting layer and emit a laser beam in a single transverse mode; an optical waveguide including the light emitting layer, the first cladding layer, and a part of the second cladding layer, the optical waveguide extending in a resonator direction; an adjustment region that adjusts a variation in a vertical divergence angle in a beam shape of the laser light emitted from the first and second light emitting units; having a beam wavelength difference between the first light-emitting unit and the second light-emitting unit is 1 to 30 nm; the adjustment region is formed at least on the light emitting end surface side of the optical waveguide, and includes a first adjustment region formed in the first light emitting portion and a second adjustment region formed in the second light emitting portion, the first and second adjustment regions being formed in the light emitting layer corresponding at least to the first and second light emitting portions, respectively; a first wavelength of the first laser light emitted from the first light-emitting unit is longer than a second wavelength of the second laser light emitted from the second light-emitting unit; a length of the first adjustment region in the resonator direction is longer than a length of the second adjustment region in the resonator direction; the light emitting layer is composed of a crystal layer of (Al x Ga 1-x ) 1-y In y P (0≦x<1, 0<y<1), the laser light is a red laser light having a wavelength λ of 600≦λ≦700 nm, In the first and second light emitting sections, the thickness of the light emitting layer is thicker and the length of the adjustment region is longer as the wavelength of the laser light is larger. Semiconductor laser device.

2. 2. The semiconductor laser device according to claim 1, wherein the band gap energy of each of the first and second adjustment regions is wider than the band gap energy of each of the light emitting layers located at a central portion in the resonator direction.

3. 2. The semiconductor laser device according to claim 1, wherein the equivalent refractive index of each of the first and second adjustment regions is lower than the equivalent refractive index in each of the waveguides located at a central portion in the resonator direction.

4. 2. The semiconductor laser device according to claim 1, wherein the thicknesses of the light emitting layers in the first and second adjustment regions are different from the thicknesses of the light emitting layers located in a central portion in the resonator direction.

5. 5. The semiconductor laser device according to claim 4, wherein the thickness of each of the light emitting layers in the first and second adjustment regions is thinner than the thickness of each of the light emitting layers located at a central portion in the resonator direction.

6. 2. The semiconductor laser device according to claim 1, wherein a composition of each of said light emitting layers in said first and second adjustment regions is different from a composition of each of said light emitting layers located in a central portion in the resonator direction.

7. The first and second adjustment regions are regions mixed with zinc (Zn), 7. The semiconductor laser device according to claim 6, wherein the concentration of said zinc is gradually decreased from said light emitting end face toward said resonator.

8. 2. The semiconductor laser device according to claim 1, further comprising a light reflecting end face formed on the opposite side of the light emitting end face in the resonator direction, wherein regions having the same configuration as the first and second adjustment regions are formed on the light reflecting end face side, the regions having different lengths in the resonator direction.

9. 2. The semiconductor laser device according to claim 1, wherein a length in the resonator direction of a gain region disposed in a central portion of said optical waveguide is the same in said first and second light emitting portions.

10. A semiconductor laser device as described in claim 1, wherein the first light-emitting portion and the second light-emitting portion have equal distances from the lower surface of each light-emitting layer to the upper surface of the substrate.

11. A method for manufacturing the semiconductor laser device according to claim 1, comprising the steps of: A step (1) of forming an n-type cladding layer as the first cladding layer on the substrate; (2) forming a mask on the n-type cladding layer; (3) forming the light emitting layer by selective growth; (4) forming a p-type cladding layer as the second cladding layer and a capping layer; and (5) forming a ridge and an electrode as a part of the optical waveguide and dividing the optical waveguide into individual pieces. The step (4) further includes a step of removing the mask. A method for manufacturing a semiconductor laser device.

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