Semiconductor laser device and its manufacturing method

Abstract

To provide a semiconductor laser device capable of suppressing a practical problem caused by height difference in a chip.SOLUTION: A semiconductor laser device LD001 comprises a substrate 1, a first clad layer 2 of a first conductivity type and a second clad layer 3 of a second conductivity type laminated on a principal surface of the substrate, and a light-emitting layer EL formed so as to be sandwiched between the first clad layer 2 and the second clad layer 3 on a first surface parallel to the principal surface of the substrate. The light-emitting layer EL includes a plurality of light-emitting regions for emitting laser beams of a red region. A value of a peak wavelength λ in an optical spectrum of a laser beam emitted from each of the plurality of light-emitting regions differs depending on a thickness EH of the light-emitting layer EL from the first surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a semiconductor laser device and a method for manufacturing the same. [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] Moreover, in recent years, reality creation 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, and 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 improve the performance of images 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 that oscillate different wavelengths have the same composition, but the well widths (physical film thicknesses) are different. [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] To improve image quality (resolution and frame rate), a monolithic single-mode lateral laser diode that independently drives a multi-emitter (multiple light-emitting parts) with a narrow pitch is required. 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] In Patent Document 1, in order to oscillate lasers of multiple wavelengths within the same element (same chip), crystal layers of different thicknesses are selectively grown for each laser wavelength to be oscillated. Specifically, the crystal layers for oscillating each laser are formed by selectively growing an upper n-type cladding layer, a quantum well active layer, a p-type cladding layer, and a cap layer in sequence to form a striped crystal structure. Therefore, not only does the position of the oscillated laser differ due to the difference in height of the quantum well active layer, but the thickness (height) of the striped crystal layer also differs greatly. Since the cladding layer is usually formed on the order of several microns, the difference in thickness (height) of the striped crystal layer becomes more noticeable. In addition to the difference in height of the light emitting point, the difference in height of the striped crystal layer causes practical problems such as a complicated power supply structure to the laser chip.

[0010] By the way, one of the mounting methods of laser chips is the junction-down (J-down) mounting method, in which the active layer side (i.e., the stripe or ridge side) of the element is bonded to a base such as a stem, rather than the substrate side. Compared with semiconductor laser devices in the infrared wavelength region, semiconductor laser devices in the red wavelength region have a large temperature dependency of characteristics such as threshold value and efficiency due to the physical properties of the material system. Therefore, heat dissipation is important to obtain stable characteristics and high optical output, and semiconductor laser devices in the red wavelength region often adopt the J-down mounting method that allows heat dissipation from the active layer side to the submount. However, if the height of the stripe is significantly different in the laser regions of each wavelength, problems such as distortion will occur in the cladding layer during J-down mounting, reducing the reliability of the element will occur. Furthermore, problems such as tilt of the element due to the difference in the height of the stripe (ridge), variation in solder wetting, and poor bonding of the ridge with a low height will occur during J-down mounting. In addition, if the heights of the stripes (ridges) are different, problems may occur when forming an opening for contact between the electrode formed on the ridge and the p-type cladding layer. If the difference in height of the stripes (ridges) becomes significant in this way, practical problems will arise during mounting and the like.

[0011] It is an object of the present invention to provide a semiconductor laser device that suppresses practical problems caused by differences in height within a chip. 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 one embodiment of the present invention comprises a substrate, a first cladding layer of a first conductivity type and a second cladding layer of a second conductivity type stacked on a main surface of the substrate, and a light-emitting layer formed between the first cladding layer and the second cladding layer and on a first surface parallel to the main surface of the substrate, the light-emitting layer having a plurality of light-emitting regions emitting laser light in a red region, and a peak wavelength value in an optical spectrum of the laser light emitted from each of the plurality of light-emitting regions differs depending on a thickness of the light-emitting layer from the first surface. Effect of the Invention

[0013] In a semiconductor laser device according to an embodiment of the present invention, it is possible to provide a semiconductor laser device that suppresses practical problems caused by differences in height within a chip. [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 an embodiment; [Figure 2A] 11 is a perspective view showing a main part of an example of a configuration of a semiconductor laser device according to another embodiment 1. FIG. [Figure 2B] 10 is a cross-sectional view showing an example of a configuration of a main part of light-emitting layers EL01 to EL04 in a semiconductor laser device according to another embodiment 1. FIG. [Figure 3A] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing the semiconductor laser device according to the first alternative embodiment. FIG. [Figure 3B] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing the semiconductor laser device according to the first alternative embodiment. FIG. [Figure 4]10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing the semiconductor laser device according to the first alternative embodiment. FIG. [Diagram 5] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing the semiconductor laser device according to the first alternative embodiment. FIG. [Figure 6] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing the semiconductor laser device according to the first alternative embodiment. FIG. [Figure 7A] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing the semiconductor laser device according to the first alternative embodiment. FIG. [Figure 7B] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing the semiconductor laser device according to the first alternative embodiment. FIG. [Figure 7C] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing the semiconductor laser device according to the first alternative embodiment. FIG. [Figure 8A] 10 is a cross-sectional view of a main part illustrating an example of a step included in a first modified example of a method for manufacturing a semiconductor laser device according to the first alternative embodiment. [Figure 8B] 11 is a cross-sectional view of a main part illustrating an example of a process included in a second modified example of the method for manufacturing a semiconductor laser device according to the first alternative embodiment. FIG. [Figure 9A] 11 is a perspective view showing a main part of an example of a configuration of a semiconductor laser device according to another embodiment 2. FIG. [Figure 9B] 10 is a cross-sectional view showing an example of a configuration of a main part of light-emitting layers EL11 to EL13 in a semiconductor laser device according to another embodiment 2. FIG. [Figure 10A] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 10B] 11 is a perspective view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 10C] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 10D] 11 is a perspective view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 11A] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 11B] 11 is a perspective view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 12A] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 12B] 11 is a perspective view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 13A] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 13B] 11 is a perspective view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 14A] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 14B] 11 is a perspective view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 14C] 10 is a cross-sectional view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 14D] 11 is a perspective view of a main part illustrating an example of a process included in a method of manufacturing a semiconductor laser device according to another embodiment 2. FIG. [Figure 15] FIG. 2 is a diagram showing the relationship between the In composition ratio and the lasing wavelength in a quantum well layer QW formed by selective growth. [Figure 16] FIG. 2 is a diagram showing the relationship between the In composition ratio and the lasing wavelength in a quantum well layer QW formed by selective growth. [Figure 17] 1 is a diagram showing the amount of strain in Ga1-yInyP versus the In composition ratio of a quantum well layer QW. 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 one embodiment of the present invention] Fig. 1 is a perspective view of a main part showing an example of the configuration of a semiconductor laser device according to one embodiment. Note that, with respect to the x-axis, y-axis, and z-axis shown in Fig. 1, x means the horizontal direction / width direction / lateral direction, y means the depth direction / longitudinal direction, and z means the vertical direction / thickness direction / height direction, respectively. The definitions of these directions are the same in other figures.

[0017] 1, in a semiconductor laser device LD001 according to one 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. In addition, four light emitting portions EM001, EM002, EM003, and EM004 that emit laser light are formed at predetermined intervals in the x direction in FIG.

[0018] From the light emitting section EM, laser light (wavelength λ = 600 nm to 700 nm) in the red region is emitted. Preferably, from the light emitting sections EM001, EM002, EM003, and EM004, laser light with different wavelengths λ001 to λ004 is emitted within the wavelength range of the red region. Note that not all of the wavelengths λ of the laser light emitted from the light emitting section EM need to be different, as long as at least one wavelength is different from the other wavelengths. The wavelength λ shown here indicates the value of the peak wavelength in the optical spectrum of the laser light emitted from the light emitting section EM, and the same applies to the following Other Embodiments 1 and 2.

[0019] Also, the light emitting layers EL001, EL002, EL003, and EL004 in each of the light emitting sections EM001, EM002, EM003, and EM004 are formed on the same main surface of (Al x Ga 1-x ) 1-y In y P (0 ≦ x < 1, 0 < y < 1) crystal layer. The thickness EH of the crystal layers of the light emitting layers EL001, EL002, EL003, and EL004 are different from each other. Note that not all of the thicknesses EH of the light emitting layers EL need to be different, as long as at least one thickness EH of the light emitting layer EL is different from the other thicknesses EH. Here, the thickness EH of the crystal layer has the relationship of EH001 < EH002 < EH003 < EH004. In this way, depending on the thickness of the light emitting layer EL, the value of the wavelength λ of the emitted laser light also differs.

[0020] Note that in FIG. 1, a semiconductor laser device having a ridge structure was described, but it can also be applied to other semiconductor laser devices without a ridge structure, such as an embedded structure type semiconductor laser device having a current confinement layer.

[0021] [Other Embodiment 1] In another semiconductor laser device LD01 according to Embodiment 1, four light-emitting parts EM01, EM02, EM03, and EM04 that emit laser light are formed, and the widths (EW01, EW02, EW03, EW04) of the light-emitting layers EL of the respective light-emitting parts EM01, EM02, EM03, and EM04 are different. Also, the thicknesses EH of the crystal layers of the light-emitting layers EL01, EL02, EL03, and EL04 in the respective light-emitting parts EM01, EM02, EM03, and EM04 are different. Further, laser light of different wavelengths λ is emitted from the respective light-emitting parts EM01, EM02, EM03, and EM04.

[0022] (Configuration of semiconductor laser device) FIG. 2A is a perspective view of a main part showing an example of the configuration of a semiconductor laser device LD01 according to Another Embodiment 1. FIG. 2B is a cross-sectional view of a main part showing an example of the configuration of the light-emitting layers EL01 to EL04 in the semiconductor laser device according to Another Embodiment 1.

[0023] As shown in FIG. 2A, on a GaAs substrate 1, an n-type clad layer 2 (thickness 2 μm), light-emitting layers EL01, EL02, EL03, and EL04, and a p-type clad layer 3 (thickness 2 μm) are formed. The light-emitting layers EL01, EL02, EL03, and EL04 are composed of crystal layers of (Al x Ga 1-x ) 1-y In y P (0 ≦ x <1, 0 <y <1). Also, the light-emitting layers EL01, EL02, EL03, and EL04 are formed on the same plane as the n-type clad layer 2. That is, the bottom surface positions of the light-emitting layers EL01, EL02, EL03, and EL04 are the same in the vertical direction or the thickness direction (corresponding to the z direction in FIG. 2A).

[0024] In addition, four light-emitting portions EM01, EM02, EM03, and EM04 are formed in the semiconductor laser device LD01, and the widths EW of the light-emitting layers EL01, EL02, EL03, and EL04 in each light-emitting portion EM (corresponding to the size in the x direction (horizontal direction) shown in FIG. 2A) are different. That is, the widths are in the relationship of EW04 < EW03 < EW02 < EW01. As an example, the length of the width EW04 is 15 μm, the length of the width EW03 is 25 μm, the length of the width EW02 is 35 μm, and the length of the width EW01 is 45 μm. Further, the thicknesses EH of the crystal layers of the light-emitting layers EL01, EL02, EL03, and EL04 (corresponding to the size in the z direction (vertical direction) shown in FIG. 2A) are different. Specifically, the thickness EH of the light-emitting layer EL is in the relationship of EH01 < EH02 < EH03 < EH04. As an example, the thickness EH01 of the light-emitting layer EL01 is 100 nm, the thickness EH02 of the light-emitting layer EL02 is 110 nm, the thickness EH03 of the light-emitting layer EL03 is 120 nm, and the thickness EH04 of the light-emitting layer EL04 is 130 nm.

[0025] In each of the light-emitting portions EM01, EM02, EM03, and EM04, a current constriction structure (current injection structure) formed by etching and removing a part of the p-type clad layer 3 and a ridge 4 as a structure for lateral (x direction in FIG. 2A) optical confinement are formed. A p-side electrode 7P and an n-side electrode 7N are formed on the upper surface of the ridge 4 and the back surface of the GaAs substrate 1.

[0026] By applying a current to the n-side electrode 7N and the p-side electrode 7P, laser light (wavelength: 600 nm to 700 nm) in the red region is emitted from the light-emitting regions ER01, ER02, ER03, and ER04 formed in the four light-emitting portions EM01, EM02, EM03, and EM04. The wavelength λ emitted from the light-emitting region ER is different for each of the light-emitting portions EM. Specifically, the wavelength λ is in the relationship of light-emitting portion EM01 < EM02 < EM03 < EM04. As an example, laser light having wavelengths of 640 nm from the light-emitting portion EM01, 643 nm from EM02, 646 nm from EM03, and 649 nm from EM04 is emitted respectively. In this way, the greater the thickness EH of the light-emitting layer EL, the greater the value of the wavelength λ.

[0027] Although the details will be described later, the dashed line A (FIGS. 2A and 7) is illustrated to show the difference in height (z direction in FIG. 2A) of the upper surface of the ridge 4 (to be precise, the upper surface of the cap layer 5 formed on the ridge 4) formed in each light-emitting portion EM. When forming the semiconductor laser device LD01 according to the other embodiment 1, the light-emitting layers EL01, EL02, EL03, and EL04 are formed by selective growth, but the other crystal layers (n-type cladding layer 2 and p-type cladding layer 3) are formed without using selective growth. As described above, the light-emitting layers EL01, EL02, EL03, and EL04 are formed on the same surface, and the positions of their lower surfaces are the same in the vertical direction or thickness direction (corresponding to the z direction in FIG. 2A). Therefore, in the four light-emitting portions EM, as shown by the dashed line A, only the difference in thickness EH of the light-emitting layer EL occurs as a difference in the vertical direction or thickness direction (corresponding to the z direction in FIG. 2A).

[0028] Furthermore, the p-side electrode 7P formed on the upper surface of the ridge 4 may be formed with a different thickness for each light-emitting portion EM in order to compensate for the difference in height between the light-emitting portions EM. This makes the upper surface position of the p-side electrode 7P the same for each light-emitting portion EM, as shown by the dashed line B. This makes it possible to make the wettability of the solder uniform during J-down mounting, and also to prevent the chip from tilting. Furthermore, when the mounting device is used to image-recognize the chip during mounting, it is easy to focus all the beams on the electrode positions.

[0029] The pitch interval in the lateral direction (x direction in FIG. 2A) of each of the central positions of the multiple light-emitting regions ER (or central positions of the ridges 4) is selected from the range of 5 μm or more and 100 μm or less. In order to oscillate red laser light (600 to 700 nm) in a lateral single mode, the ridge width (corresponding to the x direction in FIG. 2A) needs to be about 2 μm so as to satisfy the cutoff condition of the higher mode. Therefore, taking into consideration the line and space of the multiple ridges of the multi-beam, it is preferable to set the minimum pitch interval of each of the central positions of the multiple light-emitting regions ER (or central positions of the ridges 4) to about 5 μm. In addition, in the J-down mounting, the p-side electrode 7P on the top of the ridge 4 is joined to a submount (not shown) via a joining material such as solder, and the submount is connected to a heat dissipation member.

[0030] FIG. 2B is a cross-sectional view of a main part showing an example of the configuration of light-emitting layers EL01 to EL04 in the semiconductor laser device according to the alternative first embodiment.

[0031] As shown in FIG. 2B, the light-emitting layer EL is composed of a lower n-side guide layer nGL (several tens of nm), a quantum well layer QW (several nm to several tens of nm), a barrier layer BL (several nm to several tens of nm), a quantum well layer QW (several nm to several tens of nm) and an upper p-side guide layer pGL (several tens of nm), and is formed to a total thickness of about 100 nm. The light-emitting regions ER01, ER02, ER03, and ER04 shown in FIG. 2A correspond to desired regions of the quantum well layer QW. In FIG. 2B, the quantum well layer QW is shown as a multiple quantum well layer (MQW), but may be a single quantum well layer (SQW). As an example, the lower n-side guide layer nGL and the upper p-side guide layer pGL are (Al x Ga 1-x ) 1-y In y The quantum well layer QW is made of GaInP with a thickness of 5 nm to 6 nm. The barrier layer BL is made of (AlxGa1-x)1-yInyP with a composition ratio of x = 0.7, y = 0.5, and a thickness of 5 nm to 6 nm.

[0032] In the case of expressing the light-emitting layer as EL in the present embodiment, it means that the light-emitting layer EL includes all of the above-described lower n-side guide layer nGL, quantum well layer QW, barrier layer BL, and upper p-side guide layer pGL, or means including the quantum well layer QW and the barrier layer BL, or may also mean including a part of at least one of the p-type clad layer 3 and the n-type clad layer 2.

[0033] (Method for manufacturing a semiconductor laser device) Next, an example of a method for manufacturing a semiconductor laser device LD01 according to another Embodiment 1 will be described. FIGS. 3 to 7 are cross-sectional views showing a main part of an example of the steps included in the method for manufacturing the semiconductor laser device LD01.

[0034] The method for manufacturing a semiconductor laser device LD01 according to another 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 EL01, EL02, EL03, and EL04; (4) a step of forming a p-type clad layer 3 and a cap layer 5 (including a step of removing the mask MK); and (5) a step of forming a ridge and electrodes and separating into individual chips.

[0035] (1) Step of forming an n-type clad layer 2 on a GaAs substrate 1 First, as shown in FIG. 3A, an n-type clad layer 2 having a thickness of about 2 μm is epitaxially grown on the GaAs substrate 1 by MOCVD. 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), where x = 1 and y = 0.5 in this example. In the present embodiment, considering lattice matching with the GaAs substrate 1, the In composition y is adjusted to 0.5. Also, the composition ratio of Al and Ga (x: 1 - x) is preferably such that x is larger, and (x: 1 - x) = 1: 0 may also be acceptable.

[0036] (2) Step of forming a mask MK Next, as shown in FIG. 3B, after forming the n-type clad layer 2, a silicon oxide (SiO2) film that functions as a mask MK is formed on the surface of the n-type clad layer 2 by CVD method. This SiO2 film is a film that inhibits crystal growth, and for example, a silicon nitride (Si3N4) film may be used.

[0037] After forming the SiO2 film, as shown in FIG. 4, a plurality of stripe-shaped openings (four openings in this embodiment) are formed in the SiO2 film using a lithography method. The widths of the four openings (corresponding to the sizes in the x-direction (horizontal direction) shown in FIG. 2A) are different from each other, and are formed so as to become narrower in order from the left side of FIG. 4. That is, masks MK01 to MK05 are formed so that the widths have the relationship of EW04 < EW03 < EW02 < EW01 (see FIG. 2A).

[0038] (3) Step of forming the light-emitting layers EL01, EL02, EL03, and EL04 by selective growth method Next, as shown in FIG. 5, in the region of the opening of the mask MK, light-emitting layers EL01, EL02, EL03, and EL04 composed of a lower n-side guide layer nGL, 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.

[0039] 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.

[0040] By selective growth, the lower n-side guide layer nGL, the quantum well layer QW, the barrier layer BL, the quantum well layer QW, and the upper p-side guide layer pGL are deposited in this order in the region of the opening of the mask MK, as shown in FIG. 2B. The light-emitting layer EL01 is formed in the region (EW01) where the opening of the mask MK is the widest, and the light-emitting layer EL04 is formed in the region (EW04) where the opening of the mask MK is the narrowest, as shown in FIG. 4. When the light-emitting layer EL is formed by selective growth, an inclined surface 11 is formed in the light-emitting layer EL. That is, the light-emitting layer EL has a side surface extending in the longitudinal direction of the ridge (corresponding to the y direction in FIG. 2A), and this side surface is inclined inward as the thickness of the light-emitting layer EL increases.

[0041] 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 the elements, are set as follows. 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.

[0042] In this embodiment, the composition of the guide layer GL and the barrier layer BL is x=0.7, y=0.5. In addition, the source gas TMA is not supplied in the growth of the quantum well layer QW, and the quantum well layer QW is GaInP that does not contain Al (i.e., x=0). The quantum well layer QW is formed to a thickness in the range of 5 nm to 6 nm.

[0043] 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. For a red laser, it is selected from the range of about 50 nm to about 500 nm, and in this embodiment, the total thickness is about 100 nm.

[0044] Also, the thickness EH of the light-emitting layer EL formed by the selective growth method is different for each light-emitting layer EL. That is, due to the size of the opening of the mask MK, there is a difference in the thickness of the selectively grown light-emitting layer EL. The narrower the width EW of the light-emitting layer EL, the thicker the thickness of the light-emitting layer EL. Specifically, the thickness EH has the relationship of EH01 < EH02 < EH03 < EH04.

[0045] As described above, when the light-emitting layer EL is deposited by the selective growth method in different opening regions of the mask MK, the film thickness of the light-emitting layer EL is different. Although the mechanism of this is not clear, it can be assumed to be the following (i) to (iv). (i) In the selective growth method, film growth does not occur on the surface of the mask MK. Therefore, the source gas supplied to the surface of the mask MK moves (migrate) on the surface of the mask MK and moves to the region of the opening of the mask MK. (ii) The larger the surface area of the mask MK, the larger the amount of the source gas that moves. (iii) In the region of the opening of the mask MK adjacent to the mask MK with a large surface area, a larger amount of the source gas moves to the opening, and the concentration of the source gas in the opening becomes high. Also, if the opening of the mask MK is small, the concentration of the source gas is also higher. (iv) As a result, more raw materials are supplied to the light-emitting layer EL04 formed in the region where the opening of the mask MK is the narrowest.

[0046] (4) Step of forming the p-type clad layer 3 and the cap layer 5 (including the step of removing the mask MK) Next, as shown in Fig. 6, the mask MK is removed. Then, as shown in Fig. 7A, a p-type cladding layer 3 having a thickness of about 2 µm is epitaxially grown by MOCVD, followed by the formation of a cap layer 5 having a thickness of 0.5 µm. The formation of the p-type cladding layer 3 includes a step of forming an etch stop layer 6. The etch stop layer 6 functions as an etch stop layer when the p-type cladding layer 3 is etched to form a ridge 4 in the next step (5).

[0047] (5) Forming ridges and electrodes and dividing them into individual pieces Next, as shown in FIG. 7B and FIG. 7C, the p-type cladding layer 3 is etched into a predetermined shape to form a ridge 4 for each of the light-emitting layers EL01, EL02, EL03, and EL04. In FIG. 7B, the thickness from the upper surface of the cladding layer 2 to the upper end of the ridge 4 (the end on the p-side electrode 7P side) is exaggerated, but the height (distance in the thickness direction) of the ridge 4 formed by etching is, for example, about 1 μm. Then, a passivation oxide film such as SiO2 (not shown) is formed, and an opening in the oxide film is provided on the upper part of the ridge using photolithography and etching techniques, and the p-side electrode 7P is formed thereon. In addition, an n-side electrode 7N is formed on the back surface of the GaAs substrate 1. FIG. 7C is a schematic cross-sectional view showing the semiconductor laser LD01 with the electrodes formed, and this shape corresponds to the semiconductor laser LD01 shown in the perspective view in FIG. 2A. Thereafter, the GaAs substrate is cleaved and an end face coating or the like is formed on the cleaved surface, thereby forming a semiconductor laser device LD01 as shown in FIG. 2A.

[0048] 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.

[0049] Here, the thickest light-emitting layer EL04 is about 1.2 to 1.3 times as thick as the thinnest light-emitting layer EL01. This means a difference in thickness of about 20 to 30 nm, which is a small thickness compared to the total thickness (several μm (several thousand nm)) including the GaAs substrate 1. For example, when the thickness TH from the lower surface of the n-type cladding layer 2 to the upper surface of the cap layer 5 is 4 to 5 μm (4000 to 5000 nm), the difference in thickness (20 to 30 nm) between the thickest light-emitting layer EL04 and the thinnest light-emitting layer EL01 is less than 1% of the thickness TH. In this way, by forming only the light-emitting layer EL by selective growth, the difference in height of each light-emitting portion EM can be suppressed.

[0050] (effect) The peak wavelength value in the optical spectrum of the laser light can be made different depending on the thickness of the light emitting layers EL01, EL02, EL03, and EL04 formed on the same surface. In addition, since only the light emitting layer EL is formed by selective growth in the manufacturing process of the semiconductor laser device (the n-type cladding layer and the p-type cladding layer are not formed by selective growth), the step difference in the height of the entire chip is reduced. In this way, by performing the crystal growth three times (n-type cladding layer, light emitting layer EL, and p-type cladding layer), no difference in film thickness occurs in the n-type / p-type cladding layers (about 4 μm), and only the film thickness of the light emitting layer (about 100 nm) formed relatively thinly occurs. Therefore, the difference in height of each beam position emitted from the light emitting unit EM is suppressed. Furthermore, even in the case of J-down mounting as described above, no problems occur. That is, in the first embodiment, it is possible to provide a semiconductor laser device that suppresses practical problems caused by differences in height within the chip. This makes it possible to suppress degradation of image quality due to interference of laser light, and also makes it possible to further improve visual sensitivity and image quality, such as a wide color gamut, high resolution, and wide viewing angle.

[0051] (Variation 1) A first modification of the method for manufacturing the semiconductor laser device LD01 according to the first alternative embodiment will be described. Fig. 8A is a cross-sectional view of a main part showing an example of a step included in the first modification of the method for manufacturing the semiconductor laser device according to the first alternative embodiment. Fig. 8A shows an enlarged view of a portion corresponding to the light-emitting layer EL shown in Fig. 7A.

[0052] In Modification 1 of Other Embodiment 1, as shown in Fig. 8A, a buffer layer BAL (also called a regrown interface layer) is formed immediately after step (1) and immediately after step (3). That is, the buffer layer BAL (thickness 3 nm) is formed on the surface of the n-type cladding layer 2 and the surface of the light-emitting layer EL.

[0053] As mentioned above, the red laser device contains Al (Al x Ga 1-x ) 1-y In y Although the buffer layer BAL is composed of a P crystal layer, Al is very easily oxidized. Therefore, the buffer layer BAL is formed as an oxidation prevention layer to suppress oxidation of the crystal growth interface between processes. If Al is oxidized, the rate of non-radiative recombination of carriers increases, which is undesirable because it causes performance degradation such as a decrease in luminous efficiency. In addition, the buffer layer BAL is selected from materials that do not contain Al or have a low Al mixed crystal ratio, for example, GaInP or GaAs. If GaAs is selected as the buffer layer BAL, it may be etched away immediately before the subsequent process after the buffer layer BAL is formed. This is because GaAs absorbs light, so it does not need to be present in the finished product if Al oxidation between processes is suppressed.

[0054] (Variation 2) A second modification of the method for manufacturing the semiconductor laser device LD01 according to the first alternative embodiment will be described. Fig. 8B is a cross-sectional view of a main part showing an example of a step included in the second modification of the method for manufacturing the semiconductor laser device according to the first alternative embodiment. Fig. 8B shows an enlarged view of a portion corresponding to the light-emitting layer EL shown in Fig. 7A.

[0055] In another modified example 2 of the first embodiment, as shown in FIG. 8B, the buffer layer BAL is formed in the middle of the steps (1) and (4) of the first embodiment. That is, the buffer layer BAL is formed in the middle of the formation of the n-type cladding layer 2, and after forming a mask MK thereon, the remaining n-type cladding layer 2, the light emitting layer EL, a part of the p-type cladding layer 3, and the buffer layer BAL are selectively grown in a continuous manner. Then, after the mask MK is removed, the remaining p-type cladding layer 3 and the cap layer 5 are crystal-grown in a continuous manner. Note that the p-type cladding layer 3 may include an etch stop layer 6. Through these steps, the buffer layer BAL is formed in the inside of the n-type cladding layer 2 and in the inside of the p-type cladding layer 3 at a predetermined distance from the interface with the light emitting layer EL. In this way, by providing the buffer layer BAL at a predetermined distance from the interface with the light emitting layer EL, it is possible to reduce light absorption and adjust the distribution of the refractive index. As an example of each layer, the p-type cladding layer 3 is made of AlInP and has a thickness of 2 μm. The cap layer 5 is made of GaAs and has a thickness of 0.5 μm, and the etch stop layer 6 is made of GaInP and has a thickness of 2 nm.

[0056] The above-mentioned first and second modifications can also be applied to another embodiment, embodiment 2, which will be described below.

[0057] [Another embodiment 2] In the semiconductor laser device LD1 (FIG. 9A) according to the second alternative embodiment, three light emitting portions EM11, EM12, EM13 that emit laser light are formed, and the widths (EW11, EW12, EW13) of the light emitting portions EM11, EM12, EM13 are different from each other. Laser light of different wavelengths is also emitted from the light emitting portions EM11, EM12, EM13. In addition to the thicknesses EH of the crystal layers of the light emitting layers EL11, EL12, EL13 in the light emitting portions EM11, EM12, EM13 being different from each other, the composition ratios of the crystal layers of the light emitting layers EL11, EL12, EL13 are also different from each other.

[0058] The semiconductor laser device LD1 according to the second alternative embodiment has the same configuration as the semiconductor laser device LD01 according to the first alternative embodiment, except that the composition ratios of the crystal layers of the light-emitting portions EM11, EM12, and EM13 are different. Therefore, unless otherwise specified, the following mainly describes the differences from the first alternative embodiment, and the same description will not be repeated. Note that in the second alternative embodiment, the left and right configurations of the first alternative embodiment are reversed, and the number of light-emitting portions and the etch stop layer 6 of the configuration shown in the first alternative embodiment are omitted for convenience of explanation.

[0059] Although details will be described later, for laser light in the red region, Al (aluminum) and In (indium) are added to the crystal layer of the semiconductor laser device, but in the semiconductor laser device of embodiment 2, by changing the composition ratio of In (indium) in the composition that constitutes the crystal layer, it is possible to emit multiple laser lights of different wavelengths from one chip.

[0060] (Configuration of Semiconductor Laser Device) Fig. 9A is a perspective view of a main part showing an example of the configuration of a semiconductor laser device LD1 according to another embodiment 2. Fig. 9B 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 according to another embodiment 2.

[0061] As shown in FIG. 9A, in the semiconductor laser device LD1, an n-type clad layer 2, light-emitting layers EL11, EL12, EL13, and a p-type clad layer 3 are formed on a GaAs substrate 1. Further, three light-emitting portions EM11, EM12, EM13 are formed in the semiconductor laser device LD1, and the widths of the light-emitting layers EL11, EL12, EL13 in each light-emitting portion EM (corresponding to the size in the x direction (horizontal direction) shown in FIG. 9A) are different. That is, the widths are in the relationship of EW13 < EW12 < EW11. Also, the thickness EH of the light-emitting layer EL is different for each, similar to that in the first embodiment, but the description regarding the thickness is omitted unless otherwise specified in the second embodiment. Note that the thickness EH is in the relationship of EH11 < EH12 < EH13. Furthermore, an inclined surface 11 is formed at the edge portion of the upper end of the light-emitting layer EL, similar to that in the first embodiment, but the description is omitted in the second embodiment.

[0062] In each of the light-emitting portions EM11, EM12, EM13, a current constriction structure (current injection structure) formed by etching away a part of the p-type clad layer 3 and a ridge 4 as a structure for lateral (x direction in FIG. 9A) optical confinement are formed. Note that an n-side electrode 7N and a p-side electrode 7P are formed on the back surface of the GaAs substrate 1 and the upper surface of the ridge 4.

[0063] By applying a current to the n-side electrode 7N and the p-side electrode 7P, laser light (wavelength: 600 nm to 700 nm) in the red region is emitted from the light-emitting regions ER11, ER12, ER13 formed in the three light-emitting portions EM11, EM12, EM13. The emitted wavelength λ is in the relationship of light-emitting portion EM13 > light-emitting portion EM12 > light-emitting portion EM11. As an example, laser light with wavelengths of 654 nm from the light-emitting region ER11, 658 nm from the ER12, and 662 nm from the ER13 are respectively emitted.

[0064] In the above example, each wavelength is set with a difference of 4 nm. However, the difference between these wavelengths can be appropriately selected within the range of 1 nm to 30 nm. For example, when the wavelength difference is 1 nm, laser light with wavelengths of 620 nm from the light-emitting region ER11, 621 nm from ER12, and 622 nm from ER13 is respectively emitted. Also, when the wavelength difference is 30 nm, laser light with wavelengths of 630 nm from the light-emitting region ER11, 660 nm from ER12, and 690 nm from ER13 is respectively emitted.

[0065] Also, the crystal layers of the light-emitting layers EL11, EL12, and EL13 are (Al x Ga 1-x ) 1-y In y P (0 ≦ x < 1, 0 < y < 1) crystal layers, and the In composition ratio (y) of the crystal layers in each light-emitting layer EL is different. As an example, the In composition ratio (y) of the light-emitting layer EL11 is 0.51, 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 0.59. This In composition ratio (y) is preferably selected from the range of 0.35 to 0.65, although details will be described later. Also, as will be described later, the light-emitting layer EL is composed of a plurality of layers, and the Al composition (x) is such that the quantum well layer QW is the smallest. Note that when the Al composition (x) becomes larger than about 0.5, it becomes an indirect transition type, so the Al composition (x) of the quantum well layer QW is 0.5 or less.

[0066] An example of the structure of the light-emitting layers EL11, EL12, and EL13 will be described with reference to FIG. 9B. As shown in FIG. 9B, the light-emitting layer EL is composed of a lower n-side guide layer nGL (several tens of nm), a quantum well layer QW (several nm to several tens of nm), a barrier layer BL (several nm to several tens of nm), and an upper p-side guide layer pGL (several tens of nm), and is formed with a total thickness of about 100 nm. The light-emitting regions ER11, ER12, and ER13 shown in FIG. 9A correspond to the desired regions of the quantum well layer QW. In FIG. 9B, the quantum well layer QW is shown as a single quantum well layer (SQW), but it may also be a multiple quantum well layer (MQW).

[0067] In the case of expressing the light-emitting layer as EL in the present embodiment, it means that the light-emitting layer EL includes all of the above-described lower n-side guide layer nGL, quantum well layer QW, barrier layer BL, and upper p-side guide layer pGL. In some cases, it may also mean including the quantum well layer QW and the barrier layer BL, or including a part of the p-type clad layer 3.

[0068] (Method for manufacturing a semiconductor laser device) Next, an example of a method for manufacturing a semiconductor laser device LD1 according to another Embodiment 2 will be described. FIGS. 10 to 14 are schematic diagrams showing an example of the steps included in the method for manufacturing the semiconductor laser device LD1. FIGS. 10A to 14A are cross-sectional views of main parts showing an example of the steps included in the method for manufacturing the semiconductor laser device according to another Embodiment 2. FIGS. 10B to 14B are perspective views of main parts showing an example of the steps included in the method for manufacturing the semiconductor laser device according to another Embodiment 2.

[0069] The method for manufacturing the semiconductor laser device LD1 according to another Embodiment 2 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 by a selective growth method; (4) a step of forming a p-type clad layer 3 and a cap layer 5 (including a step of removing the mask MK); and (5) a step of forming a ridge and electrodes and separating into individual chips.

[0070] (1) Step of forming an n-type clad layer 2 on a GaAs substrate 1 First, as shown in FIGS. 10A and 10B, an n-type clad layer 2 having a thickness of about 2 μm is epitaxially grown on the GaAs substrate 1 by MOCVD. 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), where x = 1 and y = 0.5 in this embodiment. In the present 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 and Ga (x: 1 - x) is preferably such that x is larger, and (x: 1 - x) = 1: 0 may also be acceptable.

[0071] (2) Step of forming mask MK Next, as shown in FIGS. 10C and 10D, after forming the n-type cladding layer 2, a silicon oxide (SiO2) film functioning as a mask MK is formed on the surface of the n-type cladding layer 2 by CVD method. This SiO2 film is a film that inhibits crystal growth, and for example, a silicon nitride (Si3N4) film may be used instead.

[0072] After forming the SiO2 film, as shown in FIGS. 11A and 11B, a plurality of stripe-shaped openings (three openings in this embodiment) are formed in the SiO2 film by lithography. The widths of the three openings are different (corresponding to the size in the x direction (horizontal direction) shown in FIG. 9A), and are formed so as to become wider in order from the left side of FIGS. 11A and 11B. That is, the widths are formed so as to satisfy the relationship of EW13 < EW12 < EW11. Also, the widths of the respective masks MK forming the three openings are formed so as to become narrower in order from the left side of FIGS. 11A and 11B (corresponding to the size in the x direction (horizontal direction) shown in FIG. 9A). As an example, the respective mask widths are set to MK4: 50 μm, MK3: 35 μm, MK2: 30 μm, and MK1: 15 μm.

[0073] (3) Step of forming light-emitting layers EL11, EL12, and EL13 by selective growth method Next, as shown in FIGS. 12A and 12B, light-emitting layers EL11, EL12, and EL13 composed of a lower n-side guide layer nGL, a quantum well layer QW, a barrier layer BL, and an upper p-side guide layer pGL are formed in the regions of the openings of the mask MK. 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 regions of the openings of the mask MK.

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

[0075] By the selective growth method, a film is formed in the region of the opening of the mask MK in the order of the lower n-side guide layer nGL, quantum well layer QW, barrier layer BL, and upper p-side guide layer pGL. An emission layer EL11 is formed in the region (EW11) where the opening of the mask MK is the widest, and an emission layer EL13 is formed in the region (EW13) where the opening of the mask MK is the narrowest. Also, an emission layer EL12 is formed in the region (EW12) of the intermediate opening.

[0076] In the step of forming this emission layer EL, (Al x Ga 1-x ) 1-y In y P is formed by the selective growth method, and the values of x and y indicating the composition ratio of the elements are set as follows.

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

[0078] In this embodiment, the compositions of the guide layer GL and the barrier layer BL are (Al x Ga 1-x ) 1-y In yThe quantum well layer QW is made of P, with a composition ratio of x=0.7, y=0.5, and a thickness of, for example, 50 nm to 60 nm. In addition, in the growth of the quantum well layer QW, the source gas TMA is not supplied, the quantum well layer QW does not contain Al (i.e., x=0), and the layer composition is GaInP. The quantum well layer QW is formed to a thickness in the range of 5 nm to 6 nm.

[0079] The light-emitting layer EL formed by the selective growth method functions as a core layer of 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 is set to a total thickness of about 100 nm in this embodiment.

[0080] In the process of forming the light-emitting layer EL, the growth rate by selective growth is set higher than the normal rate. For example, if the normal growth rate is 1 to 2 μm / h, in this embodiment, the supply amount of the raw material gas is increased to increase the growth rate to about 1.2 to 1.8. By increasing the growth rate in this manner, the In composition in the light-emitting layers EL11, EL12, and EL13 can be controlled. Specifically, the In composition is highest in the light-emitting layer EL13 formed in the region (EW13) where the opening of the mask MK is the narrowest, followed by the light-emitting layer EL12 and the light-emitting layer EL11 in that order. In this manner, conditions are used that result in a high In composition in the stripe with the narrowest opening width of the mask MK.

[0081] The mechanism by which the In composition can be controlled in each of the light-emitting layers EL11, EL12, and EL13 is not clear, but it can be assumed to be the following (i) to (iv). (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 on 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 small, the concentration of the source gas becomes higher. (iv) As a result, more In is taken in the light-emitting layer EL13 formed in the region where the opening of the mask MK is narrowest. In this way, the composition ratio of each opening is adjusted by utilizing the phenomenon that the lateral diffusion of the source gas on the surface of the mask MK is promoted and the composition of the source material (for example, TMI containing In) that is particularly susceptible to lateral diffusion becomes high.

[0082] The thicknesses of the light-emitting layers EL are in the following relationship: light-emitting layer EL11<light-emitting layer EL12<light-emitting layer EL13.

[0083] (4) A step of forming a p-type cladding layer 3 and a cap layer 5 (including a step of removing the mask MK) Next, as shown in Figures 13A and 13B, the mask MK is removed. Then, as shown in Figures 14A and 14B, a p-type cladding layer 3 having a thickness of about 2 μm is epitaxially grown by MOCVD, followed by forming a cap layer 5 having a thickness of 0.5 μm.

[0084] (5) Forming ridges and electrodes and dividing them into individual pieces Next, as shown in Figures 14C and 14D, the p-type cladding layer 3 is etched into a predetermined shape to form a ridge 4 for each of the light-emitting layers EL11, EL12, and EL13. Then, a passivation oxide film such as SiO2 (not shown) is formed, and an opening is provided in the oxide film at the top of the ridge using photolithography and etching techniques, and an n-side electrode 7P is formed thereon. Also, an n-side electrode 7N is formed on the back surface of the GaAs substrate 1. Thereafter, the GaAs substrate is cleaved, and an end face coating or the like is formed on the cleaved surface to form a semiconductor laser device LD1 as shown in Figure 9A.

[0085] (Relationship between oscillation wavelength and composition ratio (In composition ratio)) Next, the relationship between the oscillation wavelength and the composition ratio (In composition ratio) will be described with reference to Figs. 15 to 17. Figs. 15 and 16 are diagrams showing the relationship between the In composition ratio and the oscillation wavelength in the quantum well layer QW formed by the selective growth method. Fig. 17 shows the relationship between the Ga composition ratio and the In composition ratio of the quantum well layer QW. 1-y In y FIG. 13 is a diagram showing the distortion amount of P.

[0086] 15 and 16 show the fundamental relationship between the oscillation wavelength and the composition ratio (In composition ratio), and the data was obtained by forming the quantum well layer QW to have a large thickness (for example, 20 nm or more) so that the thickness of the quantum well layer QW does not affect the oscillation wavelength (the quantum well layer QW in the second embodiment is 5 nm to 6 nm). Therefore, Fig. 15 and Fig. 16 do not completely match the structure (dimensions, etc.) of the semiconductor laser device LD1 in the second embodiment.

[0087] FIG. 15 shows the results of selective growth conditions in step (3) for light-emitting portions EM11, EM12, and EM13 of different widths (corresponding to the opening width EW of mask MK in FIGS. 11A and 11B) when the lateral diffusion is increased (plotted with ◆ in the figure) and decreased (plotted with ■ in the figure). FIG. 16 shows specific numerical results for FIG. 15. As shown in FIG. 15, when the lateral diffusion is decreased (plotted with ■ in the figure), there is almost no change in the oscillation wavelength in the light-emitting portions EM11, EM12, and EM13. On the other hand, when the lateral diffusion is increased (plotted with ◆ in the figure), it can be seen that the oscillation wavelength changes in each of the light-emitting portions EM11, EM12, and EM13. As shown specifically in FIG. 16, the quantum well layer QW(Ga 1-y In y The In composition ratio y of the GaAs / GaP is 0.51, and the emission wavelength is 654 nm. 1-y In y The In composition ratio y of the GaAs / GaP is 0.55, and the oscillation wavelength is 658 nm. 1-y In y The In composition ratio y of the quantum well layer QW(Ga P) is 0.59, and the oscillation wavelength is 662 nm. 1-y In y The lasing wavelength can be controlled by changing the In composition ratio y of the active layer EL below the ridge 4. Note that the above-mentioned In composition ratio indicates the value in the active layer EL below the ridge 4.

[0088] FIG. 17 shows the Ga composition ratio versus In composition ratio in the quantum well layer QW. 1-y In y 17 is a diagram showing the amount of strain in Ga. As shown in FIG. 17, the amount of strain also changes when the In composition ratio is changed from 0.5 (amount of strain 0%). As shown in FIG. 15 and FIG. 16, the oscillation wavelength can be adjusted by the In composition ratio, but as the amount of strain increases, the quality of the active layer deteriorates and the light emission efficiency decreases. Therefore, Ga 1-y In yAlthough it depends on the thickness of P, the amount of strain of the quantum well layer QW having a thickness of about 10 nm is preferably in the range of -2.0% to +2.5%, and in that case, the In composition ratio is 0.35 to 0.65. That is, the In composition ratio of the quantum well layer QW in the light-emitting layer EL is preferably selected from the range of 0.35 to 0.65. When the In composition ratio of the quantum well layer QW is 0.35, the oscillation wavelength is 620 nm, and when the In composition ratio is 0.65, the oscillation wavelength is 690 nm. In this way, by changing the In composition ratio, it is possible to control the oscillation wavelength at least in the range from 620 nm to 690 nm.

[0089] Next, the inventors will explain how, in alternative embodiment 2, they came to change (control) the oscillation wavelength by changing not only the film thickness of the light-emitting layer but also the composition ratio of the crystals in the light-emitting layer EL.

[0090] The present inventors recognized that the wavelength can be changed by changing the thickness of the light-emitting layer and by changing the composition of the light-emitting layer. In addition, the inventors found that the shorter the wavelength, the smaller the amount of change in wavelength relative to the thickness of the light-emitting layer. For example, in the case of a wavelength band in the red region, the quantum well layer QW has a thickness of about 5 nm, and there is a limit to the amount of change in wavelength (adjustment range) by adjusting the thickness, and it was concluded that there is a possibility that sufficient wavelength difference cannot be secured by adjusting the thickness alone. Therefore, the present inventors have focused on controlling the wavelength by changing the energy band gap by utilizing the composition difference of the light emitting layer in addition to changing the film thickness of the light emitting layer.

[0091] Here, the red wavelength band (Al x Ga 1-x ) 1-y In y The P active layer is composed of at least Al and In (Al x Ga 1-x ) 1-y In yA cladding layer of P mixed crystal is necessary. In order to change the energy band gap, if the composition ratio (amount introduced) of Al is increased, technical difficulties in the process may occur as shown in the following (1) and (2). (1) Al is easily oxidized, so that the interface treatment in the selective growth process becomes difficult. (2) Al is likely to form poly deposits on the mask during selective growth, so that it becomes difficult to control the composition of the crystal to be grown. Therefore, the inventors of the present invention found that, in order to change the energy band gap, it is effective in both the controllability of the wavelength change amount and the advantage in the process, particularly by adjusting the In composition ratio in the crystal. That is, by changing the In composition ratio in the composition constituting the crystal layer, it becomes possible to easily emit multiple laser beams of different wavelengths from one chip.

[0092] (effect) The semiconductor laser device LD1 according to the second embodiment also has the same effects as the semiconductor laser device LD01 according to the first embodiment. In the semiconductor laser device LD1 according to the second embodiment, the wavelengths emitted from the three light-emitting portions EM11, EM12, and EM13 can be changed by forming the light-emitting layers EL having different composition ratios according to the widths of the light-emitting layers EL11, EL12, and EL13. This makes it possible to suppress deterioration in image quality due to interference of laser light, and further improve visibility and image quality, such as a wide color gamut, high resolution, and wide viewing angle.

[0093] The present invention has been described above in detail 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 spirit 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 can also 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. In addition, the above embodiments have been described with respect to a semiconductor laser device of GaAs (substrate) / AlGaInP (crystal layer), but the present invention can also be applied to semiconductor laser devices of GaAs / AlGaAs, GaAs / InGaAsP, and GaN / AlGaN. 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.

[0094] 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.

[0095] The above embodiment also includes the following configurations.

[0096] (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; the light-emitting layer has a plurality of light-emitting portions that emit laser light in a red region, a peak wavelength value in an optical spectrum of the laser light emitted from each of the plurality of light emitting portions differs depending on a thickness of the light emitting layer from the first surface.

[0097] (Appendix 2) 2. The semiconductor laser device according to claim 1, A semiconductor laser device in which the value of a peak wavelength in the optical spectrum of the laser light emitted from each of the plurality of light emitting portions becomes longer as the thickness of the light emitting layer from the first surface becomes larger.

[0098] (Appendix 3) 2. The semiconductor laser device according to claim 1, the light emitting layer is divided and formed on the first surface so as to separate the plurality of light emitting portions from each other; A semiconductor laser device, wherein the second cladding layer formed on the light emitting layer is formed to the same thickness on each of the plurality of light emitting portions.

[0099] (Appendix 4) 2. The semiconductor laser device according to claim 1, The semiconductor laser device further comprises a buffer layer formed between the first cladding layer and the light emitting layer, and between the light emitting layer and the second cladding layer.

[0100] (Appendix 5) 2. The semiconductor laser device according to claim 1, The semiconductor laser device further comprises a buffer layer formed in the first cladding layer and in the second cladding layer.

[0101] (Appendix 6) 5. The semiconductor laser device according to claim 4, The light emitting layer has a quantum well layer, and the buffer layer has a thickness smaller than that of the quantum well layer.

[0102] (Appendix 7) 2. The semiconductor laser device according to claim 1, A ridge is formed on the upper portion of the light emitting layer, The light emitting layer has side surfaces extending in the longitudinal direction of the ridge, the side surfaces being inclined inward as the thickness of the light emitting layer increases.

[0103] (Appendix 8) 2. The semiconductor laser device according to claim 1, A semiconductor laser device in which the distance between each of the plurality of light emitting sections is within a range of 5 μm or more and 100 μm or less.

[0104] (Appendix 9) 2. The semiconductor laser device according to claim 1, a ridge is formed on an upper portion of the light emitting layer so as to correspond to the plurality of light emitting portions; an electrode is formed on top of each of the ridges, each of the electrodes having a different thickness; a dimension in a thickness direction from a main surface of the substrate to an upper end surface of the electrode is the same for each of the ridges corresponding to the plurality of light emitting portions;

[0105] (Appendix 10) 2. The semiconductor laser device according to claim 1, a ridge is formed on an upper portion of the light emitting layer so as to correspond to the plurality of light emitting portions; the ridge is bonded to a submount via a bonding material at the electrode portion; The submount is connected to a heat dissipation member.

[0106] (Appendix 11) A step (A) of forming a first cladding layer of a first conductivity type on a main surface of a substrate; A step (B) of forming a mask layer having a predetermined opening on a main surface of the first cladding layer; a step (C) of selectively growing a light emitting layer having a plurality of light emitting portions emitting laser light in a red region on the main surface of the first cladding layer in the opening regions of the mask; a step (D) of removing the mask layer after the light emitting layer is grown; (E) forming a second cladding layer and a capping layer of a second conductivity type over the first cladding layer and the upper surface of the light emitting layer; a step (F) of forming a ridge portion in a predetermined region by etching away a portion of the second cladding layer and the cap layer; A method for manufacturing a semiconductor laser device comprising the steps of:

[0107] (Appendix 12) 12. The method for manufacturing a semiconductor laser device according to claim 11, A method for manufacturing a semiconductor laser device, comprising the step (G) of forming a buffer layer after each of the steps (A) and (C).

[0108] (Appendix 13) 12. The method for manufacturing a semiconductor laser device according to claim 11, A method for manufacturing a semiconductor laser device, comprising the step (G) of forming a buffer layer midway through each of the steps (A) and (E). [Explanation of symbols]

[0109] BL Barrier Layer BAL Buffer layer EM light emitting part EL light-emitting layer ER light emission region EW Emission layer width EH Thickness of the luminescent layer 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. Ridge 5 Cap Layer 6 Etch stop layer 7P p side electrode 7N n-side electrode 11 Slope

Claims

1. A substrate; a first clad layer of a first conductivity type and a second clad layer of a second conductivity type having a conductivity type different from the first conductivity type, the first clad layer and the second clad layer being 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; having the light-emitting layer has a plurality of light-emitting regions that emit laser light in the red region, a peak wavelength value in an optical spectrum of the laser light emitted from each of the plurality of light-emitting regions differs depending on a thickness of the light-emitting layer from the first surface, and is longer as the thickness of the light-emitting layer from the first surface increases; a ridge is formed on the upper portion of the light emitting layer so as to correspond to the plurality of light emitting regions; an electrode is formed on an upper portion of each of the ridges, each of the electrodes having a different thickness, and a height in a thickness direction from a main surface of the substrate to an upper end surface of the electrode is the same for each of the ridges corresponding to the plurality of light emitting regions; Semiconductor laser device.

2. the light emitting layer is divided and formed on the first surface so as to separate the plurality of light emitting regions from each other; 2. The semiconductor laser device according to claim 1, wherein said second cladding layer formed on said light emitting layer is formed to the same thickness on each of said plurality of light emitting regions.

3. 2. The semiconductor laser device according to claim 1, further comprising a buffer layer formed between said first cladding layer and said light emitting layer and between said light emitting layer and said second cladding layer.

4. 2. The semiconductor laser device according to claim 1, further comprising a buffer layer formed in said first cladding layer and in said second cladding layer so as to be interposed therebetween.

5. 4. The semiconductor laser device according to claim 3, wherein the light emitting layer has a quantum well layer, and the buffer layer has a thickness smaller than that of the quantum well layer.

6. 2. The semiconductor laser device according to claim 1, wherein said light emitting layer has side surfaces extending in a longitudinal direction of said ridge, said side surfaces being inclined inwardly as the thickness of said light emitting layer increases.

7. 2. The semiconductor laser device according to claim 1, wherein the distance between each of the plurality of light emitting regions is in the range of 5 [mu]m to 100 [mu]m.

8. the ridge is bonded to a submount via a bonding material at the electrode; 2. The semiconductor laser device according to claim 1, wherein the submount is connected to a heat dissipating member.

9. A step (A) of forming a first cladding layer of a first conductivity type on a main surface of a substrate; A step (B) of forming a mask layer having a plurality of openings on a main surface of the first cladding layer, the opening areas each having a different width; a step (C) of selectively growing an emission layer having a plurality of emission regions emitting laser light in a red region on the main surface of the first cladding layer in the opening regions of the mask layer; a step (D) of removing the mask layer after the growth of the light emitting layer; (E) forming a second cladding layer and a capping layer of a second conductivity type over the first cladding layer and the upper surface of the light emitting layer; a step (F) of forming a ridge portion in a predetermined region by etching away a portion of the second cladding layer and the cap layer; a step (G) of forming electrodes on the upper portions of the ridge portions, the electrodes being formed to different thicknesses so that the heights in the thickness direction from the main surface of the substrate to the upper end surfaces of the electrodes are the same for each of the electrodes; A method for manufacturing a semiconductor laser device comprising the steps of:

10. 10. The method for manufacturing a semiconductor laser device according to claim 9, further comprising a step (H) of forming a buffer layer after each of the steps (A) and (C).

11. 10. The method for manufacturing a semiconductor laser device according to claim 9, further comprising a step (H) of forming a buffer layer midway between said step (A) and said step (E).

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