JP4106906B2 - Semiconductor laser device and method for manufacturing semiconductor laser device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor laser element formed by selectively growing a semiconductor layer such as a compound semiconductor layer on a substrate and a method for manufacturing the semiconductor laser element, and more particularly, a semiconductor configured using a compound semiconductor layer such as a GaN-based semiconductor layer. The present invention relates to a laser element and a method for manufacturing a semiconductor laser element.
[0002]
[Prior art]
As a method of manufacturing a semiconductor laser element, a selective mask is formed on a sapphire substrate, and a semiconductor laser element or a light emitting diode is manufactured by selective growth in which a nitride semiconductor layer such as gallium nitride is grown from an opening formed in the selective mask. The technology to configure is known. In general, a sapphire substrate is often used to grow gallium nitride. However, due to lattice mismatch between the sapphire substrate and the gallium nitride to be grown, high-density dislocations may be inherent in the crystal. For this reason, the technique for forming the low-temperature buffer layer on the substrate is one means for suppressing defects generated in the crystal to be grown, and in order to reduce crystal defects, Japanese Patent Laid-Open No. 10-312971 Combined with lateral selective overgrowth (ELO). Further, as a method of forming a gallium nitride based semiconductor laser, a technique of forming a laminated structure with an inclined surface by selective growth is also known. Such a technique is described in, for example, Japanese Patent Application Laid-Open No. 11-31840. The
[0003]
In addition, each pixel is configured by combining light emitting diodes and semiconductor lasers of blue, green, and red colors, and an image display device can be configured by independently driving the pixels arranged in a matrix. Moreover, it can also be used as a white light emitting device or a lighting device by simultaneously emitting light emitting elements of blue, green, and red colors. In particular, a light emitting device using a nitride semiconductor has a band gap energy of about 1.9 eV to about 6.2 eV, and a full color display is possible with a single material. . In this specification, a nitride refers to a compound in which B, Al, Ga, In, and Ta are group III, and group V contains N, within 1% of the total or 1 × 10 ²⁰ cm ³ The following impurities may be included.
[0004]
[Problems to be solved by the invention]
First, in order to reduce threading dislocations from the substrate, in the technique of performing selective crystal growth in the lateral direction and the crystal growth method of forming a facet structure in the growth region, threading dislocations from the substrate are laterally shifted by the facet structure part, etc. The crystal defects can be greatly reduced. However, in order to form a light emitting region such as an active layer after that, selective crystal growth in the lateral direction is sufficiently performed or a facet structure is embedded, which increases the number of processes and increases the number of manufacturing steps. As a result, a problem arises that the time required for the process becomes longer.
[0005]
Further, in the gallium nitride semiconductor laser described in the above-mentioned Japanese Patent Application Laid-Open No. 11-31840 and its manufacturing method, a conductive selection mask is formed at substantially the center of the opening of the insulating selection mask, and selective growth is performed. Thus, a laminated structure having a triangular cross section can be obtained. However, the laminated structure having a triangular cross-section is only used as a high-resistance region for concentrating current mainly in the central active layer, and an S plane (1-101 plane) appears on the inclined plane. The S surface itself is excellent in the reproducibility of manufacturing, but conversely, the region to be the active layer is limited to the vicinity of the central conductive selection mask sandwiched between the laminated structures having a triangular cross section, It becomes difficult to control the film quality of the layer, and the problem arises that the reproducibility of the entire device deteriorates.
[0006]
In addition, in a semiconductor light emitting device using an inclined surface formed by other selective growth, such as a semiconductor device described in Japanese Patent Application Laid-Open No. 2000-183460, this active layer is formed by using an inclined surface as a surface on which an active layer is formed. Becomes non-parallel to the substrate, so that noise caused by return light or the like can be reduced. However, in general, when an inclined surface by selective growth is used, the composition of crystals tends to slightly shift at a position close to the substrate and a position far from the substrate even within the same inclined surface, for example, as the distance from the substrate increases. It is easy to increase the emission wavelength. Therefore, in a device that needs to keep the emission wavelength within a predetermined range, such as a semiconductor laser element, the process is required to have excellent reproducibility in relation to the emission wavelength.
[0007]
In view of the above technical problems, an object of the present invention is to provide a semiconductor laser element having a structure excellent in reproducibility in manufacturing an element and a method for manufacturing the semiconductor laser element.
[0008]
[Means for Solving the Problems]
In the semiconductor laser device of the present invention, an active layer extending along a crystal plane inclined with respect to a main surface of a substrate is sandwiched between a first conductive type semiconductor layer and a second conductive type semiconductor layer. Only , The active layer, the first conductive semiconductor layer, and the second conductive semiconductor layer have a structure formed in a substantially triangular shape or a substantially trapezoidal shape in a cross section substantially perpendicular to the crystal plane, An end surface substantially perpendicular to the crystal plane is a resonance surface, and a region that emits light is a partial region in the inclined plane of the active layer. The crystal plane inclined with respect to the substrate main surface is formed by selective growth from the substrate. It is characterized by that.
[0009]
According to the semiconductor laser device of the present invention, the active layer extended along the crystal plane inclined with respect to the main surface of the substrate has a structure sandwiched between the first conductive type semiconductor layer and the second conductive type semiconductor layer. The active layer emits light by supplying a required current to the first conductive type semiconductor layer and the second conductive type semiconductor layer. Since the active layer has an end face substantially perpendicular to the crystal plane as a resonance surface, laser oscillation is possible, but the light emitting region in the active layer is limited to a partial region that is part of the inclined plane. By doing so, it is possible to suppress variations in emission wavelength.
[0011]
Also, By forming the active layer, the first conductive semiconductor layer, and the second conductive semiconductor layer in a substantially triangular shape or a substantially trapezoidal shape in a cross section substantially perpendicular to the crystal plane, by selective growth A partial region that emits light can be formed by using the formed semiconductor layer as it is.
[0012]
According to another aspect of the present invention, there is provided a method for manufacturing a semiconductor laser device comprising: forming a first conductive semiconductor layer having a crystal plane inclined with respect to a main surface of a substrate by selective growth; and forming the first conductive semiconductor layer on the first conductive semiconductor layer. A step of forming an active layer; a step of forming a second conductive semiconductor layer on the active layer; and a part of an inclined surface on the second conductive semiconductor layer to be in contact with the second conductive semiconductor layer And a step of forming an electrode layer.
[0013]
By using the selective growth, it is possible to form a crystal plane inclined with respect to the main surface of the substrate, and by laminating the active layer on the first conductivity type semiconductor layer, the crystal plane inclined with respect to the main surface of the substrate. An active layer having can be formed. After forming the second conductivity type semiconductor layer on the active layer, an electrode layer in contact with the second conductivity type semiconductor layer is formed at a part of the inclined surface, so that the light emitting region in the active layer is inclined. It is possible to limit to a partial region which is a part of the semiconductor laser device, and it is possible to manufacture a device with excellent reproducibility by suppressing variations in emission wavelength of the semiconductor laser device.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The semiconductor laser device of the present invention has a structure in which an active layer extending along a crystal plane inclined with respect to a substrate main surface is sandwiched between a first conductive semiconductor layer and a second conductive semiconductor layer, and the crystal plane An end face substantially perpendicular to the resonance plane is a resonance surface, and a region that emits light is a partial region in the inclined plane of the active layer.
[0015]
The substrate used in the semiconductor laser device according to the present invention is not particularly limited as long as it can form a wurtzite type compound semiconductor layer, and various substrates can be used. For example, sapphire (Al ₂ O ₃ , A plane, R plane, C plane. ), SiC (including 6H, 4H, 3C), GaN, Si, ZnS, ZnO, AlN, LiMgO, LiGaO ₂ , GaAs, MgAl ₂ O ₄ , A substrate made of InAlGaN or the like, preferably a hexagonal substrate or a cubic substrate made of these materials, and more preferably a hexagonal substrate. For example, in the case of using a sapphire substrate, a sapphire substrate having a C-plane as a main surface, which is often used when growing a gallium nitride (GaN) -based compound semiconductor material, can be used. In this case, the C plane as the main surface of the substrate includes a plane orientation inclined within a range of 5 to 6 degrees. It is also possible to use a silicon substrate that is widely used in the manufacture of semiconductor devices. The substrate itself is used for supporting a semiconductor thin film being manufactured, and may have an element structure that is peeled off when an element is completed, or may be an element structure that is used for a laser element that has completed the substrate.
[0016]
The lower layer of the selective mask for selective growth may be the substrate itself, but an underlying growth layer such as a buffer layer can be included in order to obtain good crystallinity at the time of selection. As the underlying growth layer, a compound semiconductor layer can be selected, and a wurtzite type compound semiconductor is preferably selected because a facet structure is formed in a later step. Further, the compound semiconductor layer is preferably a nitride semiconductor having a wurtzite crystal structure, a BeMgZnCdS-based compound semiconductor, a BeMgZnCdO-based compound semiconductor, or the like. As the crystal layer made of a nitride semiconductor, for example, a group III compound semiconductor can be used, and further, a gallium nitride (GaN) compound semiconductor, an aluminum nitride (AlN) compound semiconductor, and an indium nitride (InN) compound semiconductor. Indium gallium nitride (InGaN) compound semiconductors and aluminum gallium nitride (AlGaN) compound semiconductors can be preferably formed, and gallium nitride compound semiconductors are particularly preferable. As an example, an undoped GaN layer may be formed on a sapphire substrate, and then a Si-doped GaN layer may be formed. In the present invention, InGaN, AlGaN, GaN, and the like do not necessarily refer to nitride semiconductors that include only ternary mixed crystals but only binary mixed crystals. For example, in InGaN, a small amount within a range that does not change the action of InGaN. Needless to say, the present invention includes Al and other impurities. Further, the plane substantially equivalent to the S plane includes a plane orientation inclined in the range of 5 to 6 degrees with respect to the S plane. Here, in this specification, nitride refers to a compound in which B, Al, Ga, In, and Ta are group III, and group V contains N, and is within 1% of the total or 1 × 10 ²⁰ cm ³ The following impurities may be included.
[0017]
Examples of the method for growing the compound semiconductor layer include various vapor phase growth methods. For example, a vapor phase such as a metal organic compound vapor phase growth method (MOCVD (MOVPE) method) or a molecular beam epitaxy method (MBE method). A growth method or a hydride vapor phase growth method (HVPE method) can be used. Among them, the MOVPE method can quickly obtain a crystal with good crystallinity. In the MOVPE method, TMG (trimethylgallium) and TEG (triethylgallium) are used as a Ga source, TMA (trimethylaluminum) and TEA (triethylaluminum) are used as an Al source, TMI (trimethylindium) and TEI (triethylindium are used as an In source. ) And the like, and gases such as ammonia and hydrazine are used as the nitrogen source. As the impurity source, silane gas is used for Si, germane gas is used for Ge, Cp2Mg (cyclopentadienylmagnesium) is used for Mg, and DEZ (diethyl zinc) is used for Zn. In the MOVPE method, an InAlGaN-based compound semiconductor can be epitaxially grown by supplying these gases to the surface of a substrate heated to, for example, 600 ° C. or more and decomposing the gases.
[0018]
In the semiconductor laser device of the present invention, a selection mask having openings that are opened in a stripe shape, for example, is formed on the surface of the compound semiconductor layer that serves as an underlying growth layer for crystal growth. The semiconductor layer is formed by selective growth so as to have a ridge line parallel to the long side. The mask is a growth inhibition film formed directly on the main surface of the substrate or on a buffer layer or other layer formed on the substrate. For example, a mask material made of an insulating film such as a silicon oxide film or a silicon nitride film is used. The The shape of the opening of the mask is, for example, a stripe shape, but may be another shape capable of obtaining a resonance surface, for example, a curved shape, a circular shape, an elliptical shape, a triangular shape, or a pentagonal shape. Alternatively, it may be a polygonal shape such as a hexagonal shape, or a complex thereof. In addition, a plurality of openings can be formed as in a normal semiconductor process.
[0019]
When such a selective growth mask or the like is formed, a semiconductor layer is formed by selective crystal growth. As an example, the semiconductor layer is formed so as to have a ridge line parallel to the long side of the opening that is opened in a stripe shape. This semiconductor layer is formed in a substantially triangular shape in a cross section substantially perpendicular to the inclined surface described later. When the selective growth conditions are changed, the cross section is formed in a substantially trapezoidal shape.
[0020]
The crystal growth in the selective growth can be performed by the same method as the method for forming the compound semiconductor layer described above. Specific examples of the growth method include various vapor phase growth methods. For example, vapor phase methods such as metal organic compound vapor phase growth method (MOCVD (MOVPE) method) and molecular beam epitaxy method (MBE method). A growth method or a hydride vapor phase growth method (HVPE method) can be used. In the MOVPE method, TMG (trimethylgallium) and TEG (triethylgallium) are used as a Ga source, TMA (trimethylaluminum) and TEA (triethylaluminum) are used as an Al source, TMI (trimethylindium) and TEI (triethylindium are used as an In source. ) And the like, and gases such as ammonia and hydrazine are used as the nitrogen source. As the impurity source, silane gas is used for Si, germane gas is used for Ge, Cp2Mg (cyclopentadienylmagnesium) is used for Mg, and DEZ (diethyl zinc) is used for Zn. The same applies to.
[0021]
In the semiconductor laser device according to the present invention, in order to form a crystal plane inclined with respect to the main surface of the substrate, the semiconductor layer is formed by selective growth so as to have, for example, a ridge line parallel to the long side of the stripe-shaped opening. Is done. The pair of crystal planes of the semiconductor layer sandwiching the ridgeline are preferably {1-101} planes or {11-22} planes or planes substantially equivalent to these planes. desirable. The pair of crystal planes are crystal planes inclined with respect to the ridge line. For example, when the main surface of the substrate or the substrate is a C + plane, the S plane or a plane substantially equivalent to the S plane, or {11− It is possible to easily form a surface substantially equivalent to the 22} plane or {11-22} plane. When selective growth is performed, the S plane and the {11-22} plane as inclined planes inclined with respect to the main surface of the substrate are stable planes that are seen when selectively grown on the C + plane, and are relatively advantageous. It is an easy side. The S + plane and the S− plane exist for the S plane in the same manner as the C + plane and the C− plane exist on the C plane. In this specification, unless otherwise specified, the S + plane is formed on the C + plane GaN. The surface is growing, and this is described as the S surface. For the S surface, the S + surface is a stable surface. The plane index of the C + plane is (0001).
[0022]
As for the S plane, when a crystal layer is formed using a gallium nitride compound semiconductor, the number of bonds from Ga to N on the S plane is 2 or 3 and the largest after the C-plane. Here, since the C-plane cannot be practically obtained on the C + plane, the number of bonds on the S-plane is the largest. For example, when nitride is grown on a sapphire substrate having a C + plane as a main surface, the surface of a wurtzite nitride is generally a C + plane, but the S plane is stably formed by utilizing selective growth. The N bond, which tends to desorb in a plane parallel to the C + plane, is bonded from Ga by a single bond, whereas the inclined S plane is bonded by at least one pound. It will be. Therefore, the V / III ratio is effectively increased, which is advantageous for improving the crystallinity of the laminated structure. Further, when growing in a different direction from the substrate, dislocations extending upward from the substrate may be bent, which is advantageous for reducing defects.
[0023]
When the longitudinal direction of the stripe-shaped opening of the selective growth mask is the [11-20] direction or the [1-100] direction, the semiconductor layer is easily formed to have a ridge line parallel to the longitudinal direction of the opening. be able to. In addition, an opening having a stripe shape with a direction inclined by an angle of 0.2 degrees or more and 20 degrees or less from either the [11-20] direction or the [1-100] direction as a longitudinal direction is selectively grown. It can also be used. When the direction is inclined by the required angle in this way, the crystal steps tend to be aligned over the entire crystal face, and by forming an electrode in the portion where the crystal steps are aligned, each element is formed. The variation can be greatly reduced. [11-20] direction in which the longitudinal direction of the opening is almost not displaced at an angle of less than 0.2 degrees from either the [11-20] direction or the [1-100] direction. Alternatively, it shows only the same crystallinity tendency as the [1-100] direction itself. Further, when an opening having a longitudinal direction that is inclined by an angle exceeding 20 degrees is used, the influence of the steps of other crystals can be exposed to the crystal plane.
[0024]
In such a semiconductor layer, a first conductivity type semiconductor layer, an active layer, and a second conductivity type semiconductor layer are stacked on inclined surfaces formed on both sides of the ridge line. The first conductivity type semiconductor layer may be formed continuously with the underlying semiconductor layer. In the first conductivity type semiconductor layer, the active layer, and the second conductivity type semiconductor layer stacked on the inclined surface, the first conductivity type is p-type or n-type, and the second conductivity type is the opposite conductivity type. is there. For example, when the crystal layer constituting the S plane is composed of a silicon-doped gallium nitride compound semiconductor layer, the n-type semiconductor layer is composed of a silicon-doped gallium nitride compound semiconductor layer, and an InGaN layer is formed thereon as an active layer. Further, a magnesium hetero-doped gallium nitride compound semiconductor layer can be formed thereon as a p-type semiconductor layer to form a double heterostructure. It is also possible to adopt a structure in which an InGaN layer as an active layer is sandwiched between AlGaN layers or a structure in which an AlGaN layer is formed only on one side. The active layer may be composed of a single bulk active layer, but a quantum well such as a single quantum well (SQW) structure, a double quantum well (DQW) structure, or a multiple quantum well (MQW) structure. A structure may be formed. In the quantum well structure, a barrier layer is used in combination for separating the quantum well as necessary. When the active layer is an InGaN layer, the structure is easy to manufacture, especially in the manufacturing process, and the light emission characteristics of the device can be improved. Furthermore, this InGaN layer is particularly easy to crystallize in the growth on the S plane, which is a structure in which nitrogen atoms are not easily detached, and the crystallinity is improved, so that the luminous efficiency can be increased. Nitride semiconductors are non-doped and have n-type properties due to nitrogen vacancies formed in the crystal, but usually by doping a donor impurity such as Si, Ge, or Se during crystal growth, A preferred n-type can be obtained. In order to make the nitride semiconductor p-type, it can be obtained by doping the crystal with acceptor impurities such as Mg, Zn, C, Be, Ca, Ba, etc. In order to obtain a p-layer with a high carrier concentration. After doping with acceptor impurities, annealing is preferably performed at 400 ° C. or higher in an inert gas atmosphere such as nitrogen or argon. There is also a method of activation by electron beam irradiation, which is active by microwave irradiation or light irradiation. There is also a way to make it.
[0025]
The first conductive type semiconductor layer, the active layer, and the second conductive type semiconductor layer extend in a plane parallel to the inclined plane. The formation in the plane parallel to the inclined plane is inclined. This can be done easily by continuing crystal growth where the surface is formed. The first conductivity type cladding layer can be made of the same material and the same conductivity type as the crystal layer constituting the S plane, and is formed while continuously adjusting the concentration after forming the crystal layer constituting the S plane. As another example, a structure in which a part of the crystal layer constituting the S plane functions as the first conductivity type semiconductor layer may be used.
[0026]
Electrodes are directly or indirectly connected to the first conductive semiconductor layer and the second conductive semiconductor layer sandwiching the active layer. In the semiconductor laser device according to the present invention, the light emitting region is set to a partial region in the inclined plane of the active layer. The partial region is not formed in the entire region in the in-plane direction of the inclined surface, but indicates a region formed only in a partial range. Such a partial region may be formed at one location in the direction within the inclined surface, or may be configured at a plurality of locations in the direction within the inclined surface. A part of the region substantially contributes to light emission, and as described below, it is possible to narrow the electrode to narrow the current, or to concentrate the current using an insulating film. .
[0027]
The width in the in-plane direction of such a partial region is desirably set in a range in which the variation in emission wavelength of the semiconductor laser element is about 10 nm or less. As described above, according to the experimental data conducted by the present inventors, the spectrum having a half-value width of about 20 nm or less is set as the reason why the width is set within a range in which the variation in the emission wavelength of the semiconductor laser element is about 10 nm or less. This is because the active layer can easily oscillate, and in this case, it can be inferred that the peak wavelength width allowed in the electrode stripe is within 10 nm, which is its half-value width.
[0028]
According to an empirical rule, such a width is set such that a part of the gallium nitride compound semiconductor layer has a width of about 3 μm or less, preferably 2 μm or less, more preferably in the in-plane direction. Is set to a width of 1 μm or less. That is, according to the experiment conducted by the present inventors, the range that can have the above-mentioned wavelength distribution of 10 nm is shown in FIG. 14 from the relationship between the height from the bottom of a typical pyramid and the emission peak wavelength. It is. FIG. 14 is a characteristic diagram in which the horizontal axis is the length from the bottom (μm) and the vertical axis is the peak wavelength (nm). The length from the bottom is the length along the slope and corresponds to the height. According to FIG. 14, when the peak shift is about 10 nm, the height is about 3 μm at a position where the length from the base is relatively long, that is, a position away from the base to some extent. As a result, the variation in the emission wavelength of the laser element is reduced.
[0029]
As a partial region structure, an electrode for supplying a current to the active layer can be formed to have a predetermined width in the direction within the inclined plane, or the first conductive semiconductor layer and the first layer sandwiching the active layer can be formed. It is also possible to form at least one of the two-conductivity type semiconductor layers so as to have a predetermined width in the direction in the inclined plane, or to form the active layer so as to have a predetermined width in the direction in the inclined plane. As a method for reducing the width of the electrode for supplying current to the active layer, the width of the electrode layer and the first and second conductive semiconductor layers can be reduced by photolithography. In order to effectively narrow the insulating film, an insulating film may be formed in a portion opened in a stripe shape for current confinement.
[0030]
Here, each electrode is formed for each element, but one of the p-electrode and the n-electrode can be shared among a plurality of laser elements. In order to reduce the contact resistance, a required contact layer may be formed, and then an electrode may be formed on the contact layer. In general, each electrode is formed by depositing a multilayer metal film by vapor deposition or the like, but can be finely processed by lift-off or the like using photolithography in order to classify each element. Each electrode can be formed on one surface of the selective crystal growth layer or the substrate, or electrodes can be formed on both sides so that the electrodes are wired at a higher density. The independently driven electrodes may be formed by finely processing the same material, but it is also possible to use different electrode materials for each region.
[0031]
In the semiconductor laser device of the present invention, a resonator is formed on the end face of the stripe-shaped crystal growth portion. As is well known, the resonator can be formed by cleaving the crystal. For example, the resonator surface can be formed by cleaving the resonance surface in a plane substantially perpendicular to the longitudinal direction of the stripe-shaped opening. it can. Even when the resonance surface is not formed by cleavage, the resonance surface may be formed by an etching method or the like.
[0032]
Moreover, a display apparatus can be comprised by forming so that the semiconductor laser element of this invention may be arranged in multiple numbers. In a display device in which a plurality of such semiconductor laser elements are arranged, the light emitting elements can be arranged at a high density, and the ease of manufacturing due to the common use of electrodes is improved. In addition, the display device is not limited to a display device that emits light of a single color, and a display device that emits light of multiple colors can be configured.
[0033]
Hereinafter, the present invention will be described in more detail with reference to each embodiment. The semiconductor laser device of the present invention can be modified and changed without departing from the gist thereof, and the present invention is not limited to the following embodiments.
[0034]
[First embodiment]
FIG. 1 is a cross-sectional view of an essential part of a gallium nitride compound semiconductor laser device of this embodiment. A selection mask 12 made of, for example, a silicon oxide film is formed on a base 11 which is a laminate of a sapphire substrate and a base growth layer with the substrate main surface. Specifically, the base 11 is a structure in which, for example, an undoped GaN layer and a silicon-doped GaN layer are stacked on a sapphire substrate whose principal surface is a C-plane. An AlN layer or the like may be formed as the buffer layer. In the selection mask 12, an opening 13 having a stripe shape is formed by hydrofluoric acid etching after forming a resist mask. In the present embodiment, the longitudinal direction of the opening 13 is the [1-100] direction or the [11-20] direction in order to achieve crystal growth with a ridge line.
[0035]
From the elongated strip-shaped opening 13, a silicon-doped GaN layer 14 is formed as a first conductivity type semiconductor layer by selective growth. In the present embodiment, the silicon-doped GaN layer 14 has a substantially triangular cross section, and the direction perpendicular to the cross section shown in the figure is the longitudinal direction in order to grow from the elongated strip-shaped opening 13. Resonant surfaces are formed by cleavage or etching at both ends of the longitudinal direction (not shown), and laser oscillation is possible. In the silicon-doped GaN layer 14, the plane formed by the hypotenuse having a substantially triangular cross section is a crystal plane inclined with respect to the main surface of the substrate. During the growth of the silicon-doped GaN layer 14, the growth temperature is set to 980 ° C., for example.
[0036]
On the silicon-doped GaN layer 14, In _0.05 Ga _0.95 The N layer 15 is formed as a guide layer with a film thickness of 10 nm, for example. _0.05 Ga _0.95 On the N layer 15, In is used as an active layer. _0.2 Ga _0.8 The N layer 16 is formed with a film thickness of 3 nm, for example, and its In _0.2 Ga _0.8 On the N layer 16, In is used as a guide layer. _0.05 Ga _0.95 The N layer 17 is formed with a film thickness of 10 nm, for example. These In _0.05 Ga _0.95 N layer 15, In _0.2 Ga _0.8 N layer 16 and In _0.05 Ga _0.95 The N layer 17 is formed so as to be stacked on the inclined surfaces on both sides across the ridge line of the silicon-doped GaN layer 14 corresponding to the apex having a substantially triangular cross section.
[0037]
In as a guide layer _0.05 Ga _0.95 On the N layer 17, a magnesium-doped GaN layer 18 is formed as a second conductivity type semiconductor layer. The magnesium-doped GaN layer 18 is a layer that functions as a second conductivity type semiconductor layer, and is a p-type compound semiconductor layer. An insulating film 21 such as a silicon oxide film is formed on the magnesium-doped GaN layer 18. The insulating film 21 is formed so as to cover a semiconductor layer having a triangular cross section, and an opening 20 is formed by opening a part on the inclined surface of the insulating film 21. The opening 20 extends in the horizontal direction, and faces the semiconductor layer at the height where the opening 20 exists. The width on the slope of the opening 20 is set to be narrow, for example, about 1 to 3 μm.
[0038]
A p-side electrode layer 19 is formed in the region where the opening 20 is formed. The p-side electrode layer 19 has a laminated structure of, for example, Ni / Pt / Au or Ni (Pd) / Pt / Au. The p-side electrode layer 19 is formed on the entire surface, and then formed into a thin strip pattern by a technique such as etching or lift-off. The p-side electrode layer 19 partially formed on this inclined surface is deposited on the interface of the magnesium-doped GaN layer 18 through the opening 20 narrowed to about 1 to 3 μm, for example, as described above. A current is intensively supplied to a predetermined height portion of the triangular semiconductor layer so that a region to emit light is a partial region limited in the width direction of the slope.
[0039]
The selection mask 12 and the insulating film 21 are opened beside the semiconductor layer having a triangular cross section, and the n-side electrode layer 22 is formed. The n-side electrode layer 22 has, for example, a Ti / Al / Pt / Au electrode structure, and is electrically connected to the silicon-doped GaN layer 14 as the first conductivity type semiconductor layer via the base 11.
[0040]
FIG. 2 is a schematic diagram conceptually showing a partial region in the semiconductor laser device of this embodiment. Triangular prism-shaped semiconductor layers 28 are arranged so that the horizontal direction is the longitudinal direction, and both end faces 25 and 25 rising vertically are used as laser resonance surfaces. In the middle of the inclined surface 26 in the height direction, a partial region 27 serving as a light emitting region is formed. That is, in the semiconductor laser device of this embodiment, the partial width W is not the entire width R of the inclined surface 26. ₁ A partial region 27 is formed over the entire area. For this reason, the light generated in the partial region 27 has a suppressed variation in wavelength, and when resonated on the resonance surface, a laser element having a narrow half-value width and excellent reproducibility can be obtained. The width R of the entire area of the inclined surface 26 is, for example, a size within a range of about 5 μm to 50 μm.
[0041]
Here, with reference to FIG. 3 to FIG. 8, a method for manufacturing the semiconductor laser device according to the present embodiment will be described. First, as shown in FIG. 3, a selection mask 32 made of a silicon oxide film is formed on a base 31 that is a laminate of a sapphire substrate and a base growth layer. For example, the base 31 is a structure in which, for example, an undoped GaN layer and a silicon-doped GaN layer are stacked on a sapphire substrate whose main surface is a C-plane. The selection mask 32 is formed with openings 33 which are opened in stripes with the horizontal direction as the longitudinal direction. This horizontal direction is, for example, the [1-100] direction or the [11-20] direction.
[0042]
Next, as shown in FIGS. 4 and 5, a silicon-doped GaN layer 34 that functions as a first conductivity type semiconductor layer is formed by selective growth in which an elongated strip-shaped opening 33 is formed in the selection mask 32. FIG. 5 corresponds to the cross-sectional view taken along the line VV of FIG. 4 and is a process cross-sectional view related to the same process. By this selective growth, a silicon-doped GaN layer 34 having a substantially triangular cross section is formed. The inclined planes formed on both sides of the ridge line of the GaN layer 34 are, for example, S planes or {11-22} planes, which are crystal planes that are stably formed during selective growth.
[0043]
After the formation of the silicon-doped GaN layer 34 having a substantially triangular cross section, as shown in FIG. _0.05 Ga _0.95 The N layer 35 is formed with a film thickness of 10 nm, for example, and its In _0.05 Ga _0.95 On the N layer 35, In is used as an active layer. _0.2 Ga _0.8 The N layer 36 is formed, for example, with a film thickness of 3 nm, and its In _0.2 Ga _0.8 On the N layer 36, as a guide layer, In _0.05 Ga _0.95 The N layer 37 is formed with a thickness of 10 nm, for example. In as a guide layer _0.05 Ga _0.95 On the N layer 37, a magnesium-doped GaN layer 38 is formed as a second conductivity type semiconductor layer. These In _0.05 Ga _0.95 N layer 35, In _0.2 Ga _0.8 N layer 36, In _0.05 Ga _0.95 Since the N layer 37 and the magnesium-doped GaN layer 38 are thin films and laminated, the inclined surfaces such as the S surface of the magnesium-doped GaN layer 38 are reflected, and inclined surfaces are formed on both sides of the ridge line. Configured.
[0044]
After these semiconductor layers are stacked, as shown in FIG. 7, an insulating film 39 such as a silicon oxide film or a silicon nitride film is coated on the entire surface. The insulating film 39 is finely processed using photolithography or the like so as to open a part of the inclined surface, and the opening 40 is formed by the fine processing. At the bottom of the opening 40, the surface of the magnesium-doped GaN layer 38 is exposed in stripes. The width of the opening 40 is about 3 μm or less, preferably 2 μm or less, more preferably 1 μm or less.
[0045]
Next, as shown in FIG. 8, the p-side electrode layer 41 is formed in the region where the opening 40 is formed. The p-side electrode layer 41 has a laminated structure of, for example, Ni / Pt / Au or Ni (Pd) / Pt / Au. Hereinafter, although not shown, an n-side electrode layer is formed, and a resonance surface is formed on an end surface substantially perpendicular to the crystal plane by using cleavage or the like. The steps for forming the n-side electrode layer and the resonance surface may be performed before and after. By supplying a required current, a current is supplied from the p-side electrode layer 41 formed in a thin stripe shape, and light emission occurs only in a narrow region of the inclined crystal plane reflecting the p-side electrode layer 41.
[0046]
In such a manufacturing method, since the narrow opening 40 formed in the insulating film 39 functions as a current constriction portion, a laser element can be formed while suppressing variations in the emission wavelength. It is possible to manufacture a stable semiconductor laser element with good reproducibility.
[0047]
In the present embodiment, the opening 40 is formed by photolithography to form a partial region for limiting the light emission region in the direction within the inclined plane, and the p-side electrode layer 41 is formed with a narrow width. Although described as being formed, the insulating film 39 may be thickened to form an opening with a high aspect ratio, and the p-side electrode layer 41 may be formed with a narrow width by lift-off due to a step of the opening. Is possible. In the present embodiment, the electrodes are described as being continuous in the horizontal direction. However, the electrode or the active layer may be intermittently provided in the horizontal direction.
[0048]
[Second Embodiment]
FIG. 9 shows a cross-sectional view of the element structure of the semiconductor laser element of the second embodiment. The present embodiment is an example in which two p-side electrode layers are formed in an inclined plane, and has an element structure capable of controlling the emission wavelength to a plurality.
[0049]
A selection mask 52 made of, for example, a silicon oxide film is formed on a base 51 that is a laminate of a sapphire substrate and an underlying growth layer with the substrate main surface. Specifically, the base 51 is a structure in which, for example, an undoped GaN layer and a silicon-doped GaN layer are stacked on a sapphire substrate whose principal surface is a C-plane. An AlN layer or the like may be formed as the buffer layer. In the selection mask 52, an opening 53 having a stripe shape is formed by hydrofluoric acid etching after forming a resist mask. Also in this embodiment, the longitudinal direction of the opening 53 is set to the [1-100] direction or the [11-20] direction in order to obtain crystal growth having a ridge line, as in the above-described embodiment.
[0050]
From the elongated strip-shaped opening 53, a silicon-doped GaN layer 54 is formed as a first conductivity type semiconductor layer by selective growth. In this embodiment, the silicon-doped GaN layer 54 has a substantially triangular shape in cross section, and the direction perpendicular to the cross section shown in FIG. To do. Resonant surfaces are formed by cleavage or etching at both ends of the longitudinal direction (not shown), and laser oscillation is possible. In the silicon-doped GaN layer 54, a plane constituted by the hypotenuse having a substantially triangular cross section is a crystal plane inclined with respect to the main surface of the substrate. During the growth of the silicon-doped GaN layer 54, the growth temperature is set to 980 ° C., for example.
[0051]
On the silicon-doped GaN layer 54, In _0.05 Ga _0.95 The N layer 55 is formed as a guide layer with a thickness of 10 nm, for example. _0.05 Ga _0.95 On the N layer 55, In is used as an active layer. _0.2 Ga _0.8 The N layer 56 is formed with a film thickness of 3 nm, for example. _0.2 Ga _0.8 On the N layer 56, as a guide layer, In _0.05 Ga _0.95 The N layer 57 is formed with a thickness of 10 nm, for example. These In _0.05 Ga _0.95 N layer 55, In _0.2 Ga _0.8 N layer 56 and In _0.05 Ga _0.95 The N layer 57 is formed so as to be laminated on the inclined surfaces on both sides across the ridge line of the silicon-doped GaN layer 54 corresponding to the apex having a substantially triangular cross section.
[0052]
In as a guide layer _0.05 Ga _0.95 On the N layer 57, a magnesium-doped GaN layer 58 is formed as a second conductivity type semiconductor layer. The magnesium-doped GaN layer 58 is a layer that functions as a second conductivity type semiconductor layer, and is a p-type compound semiconductor layer. An insulating film 61 such as a silicon oxide film is formed on the magnesium-doped GaN layer 58. The insulating film 61 is formed so as to cover the semiconductor layer having a triangular cross section. Openings 66 and 67 are formed by opening two locations on the inclined surface of the insulating film 61. The openings 66 and 67 are extended in the horizontal direction, and the semiconductor layer is exposed at the portions of the openings 66 and 67. The width on the slope of the openings 66 and 67 is set to be thin, for example, about 1 to 3 μm.
[0053]
In the region where the openings 66 and 67 are formed, the p-side electrode layers 64 and 65 are formed. The p-side electrode layers 64 and 65 have a laminated structure of, for example, Ni / Pt / Au or Ni (Pd) / Pt / Au. These p-side electrode layers 64 and 65 are formed on the entire surface, and then formed into a thin strip pattern by a technique such as etching or lift-off. The p-side electrode layers 64 and 65 partially formed on the inclined surface cover the interface of the magnesium-doped GaN layer 58 through the openings 66 and 67 that are narrowly opened to, for example, about 1 to 3 μm as described above. A current is concentratedly supplied to a predetermined height portion of the semiconductor layer having a triangular cross section, and the regions to emit light are made to be partial regions 68 and 69 limited in the width direction of the slope. The p-side electrode layers 64 and 65 can be formed by patterning a film having the same laminated structure by a photolithography technique, and electrode layers having different structures and materials may be sequentially formed and finely processed.
[0054]
An n-side electrode layer 62 is formed in the opening 63 where the selection mask 52 and the insulating film 61 are opened beside the semiconductor layer having a triangular cross section. The n-side electrode layer 62 has, for example, a Ti / Al / Pt / Au electrode structure, and is electrically connected to the silicon-doped GaN layer 54 as the first conductivity type semiconductor layer via the base 51.
[0055]
In the semiconductor laser device of this embodiment having such a structure shown in FIG. 9, two electrode layers 64 and 65 are formed in the crystal plane inclined with respect to the main surface of the substrate, and the emission wavelength is generally in the inclined plane. The closer to the apex, the longer the wavelength shifts to the longer wavelength side. Therefore, the emission wavelength differs between the partial region 68 corresponding to the p-side electrode layer 64 and the partial region 69 corresponding to the p-side electrode layer 65. Can be emitted within the same element. In addition, since the narrow opening portions 66 and 67 formed in the insulating film 61 function as current confinement portions, it is possible to form a laser element while suppressing variations in the emission wavelength, and the emission wavelength is stable. Semiconductor laser elements can be manufactured with good reproducibility.
[0056]
[Third Embodiment]
FIG. 10 shows a sectional view of the element structure of the semiconductor laser element of the third embodiment. The present embodiment is an example in which p-side electrode layers are formed on two inclined surfaces that face each other across a ridge line.
[0057]
A selection mask 72 made of, for example, a silicon oxide film is formed on a base 71 that is a laminate of a sapphire substrate and an underlying growth layer with the substrate main surface. The base 71 is a structure in which, for example, an undoped GaN layer and a silicon-doped GaN layer are stacked on a sapphire substrate whose main surface is a C-plane. An AlN layer or the like may be formed as the buffer layer. In the selection mask 72, an opening 73 having a stripe shape is formed by hydrofluoric acid-based etching after forming a resist mask. Also in this embodiment, the longitudinal direction of the opening 73 is, for example, the [1-100] direction or the [11-20] direction in order to obtain crystal growth having a ridge line, as in the above-described embodiment.
[0058]
From the elongated strip-shaped opening 73, a silicon-doped GaN layer 74 is formed as a first conductivity type semiconductor layer by selective growth. Also in the present embodiment, the silicon-doped GaN layer 74 has a substantially triangular cross section and grows from an elongated strip-shaped opening 73, as in the above-described embodiments. Therefore, the direction perpendicular to the illustrated cross section is the longitudinal direction. To do. Resonant surfaces are formed by cleavage or etching at both ends of the longitudinal direction (not shown), and laser oscillation is possible. In the silicon-doped GaN layer 74, the plane constituted by the hypotenuse having a substantially triangular cross section is a crystal plane inclined with respect to the main surface of the substrate. During the growth of the silicon-doped GaN layer 74, the growth temperature is set to 980 ° C., for example.
[0059]
On the silicon-doped GaN layer 74, In _0.05 Ga _0.95 The N layer 75 is formed as a guide layer with a thickness of 10 nm, for example. _0.05 Ga _0.95 On the N layer 75, In is used as an active layer. _0.2 Ga _0.8 The N layer 76 is formed with a film thickness of 3 nm, for example, and its In _0.2 Ga _0.8 On the N layer 76, In is used as a guide layer. _0.05 Ga _0.95 The N layer 77 is formed with a thickness of 10 nm, for example. These In _0.05 Ga _0.95 N layer 75, In _0.2 Ga _0.8 N layer 76 and In _0.05 Ga _0.95 The N layer 77 is formed so as to be laminated on the inclined surfaces on both sides across the ridge line of the silicon-doped GaN layer 74 corresponding to the apex having a substantially triangular cross section.
[0060]
In as a guide layer _0.05 Ga _0.95 On the N layer 77, a magnesium-doped GaN layer 78 is formed as a second conductivity type semiconductor layer. The magnesium-doped GaN layer 78 is a layer that functions as a second conductivity type semiconductor layer, and is a p-type compound semiconductor layer. An insulating film 81 such as a silicon oxide film is formed on the magnesium-doped GaN layer 78. The insulating film 81 is formed so as to cover the semiconductor layer having a triangular cross section.
[0061]
A part of the insulating film 81 on the inclined surface is opened, and the openings 86 and 87 are formed on both inclined surfaces facing each other. These openings 86 and 87 are extended in the horizontal direction so that the semiconductor layer at the height where the openings 86 and 87 are present is exposed. The width on the slope of the openings 86 and 87 is set to be thin, for example, about 1 to 3 μm.
[0062]
P-side electrode layers 84 and 85 are formed in the regions where the openings 86 and 87 are formed. The p-side electrode layers 84 and 85 have a laminated structure of, for example, Ni / Pt / Au or Ni (Pd) / Pt / Au. These p-side electrode layers 84 and 85 are formed on the entire surface, and then formed into a thin strip pattern by a technique such as etching or lift-off. As described above, the p-side electrode layers 84 and 85 partially formed on the inclined surface cover the interface of the magnesium-doped GaN layer 78 through the openings 86 and 87 that are narrowly opened to, for example, about 1 to 3 μm. A current is concentratedly supplied to a predetermined height portion of the semiconductor layer having a triangular cross section, and the regions to emit light are made partial regions 89 and 88 limited in the width direction of the slope. The p-side electrode layers 84 and 85 can be formed by patterning a film having the same laminated structure by a photolithography technique, and electrode layers having different structures and materials may be sequentially formed and finely processed.
[0063]
An n-side electrode layer 82 is formed in the opening 83 where the selection mask 72 and the insulating film 81 are opened beside the semiconductor layer having a triangular cross section. The n-side electrode layer 82 has, for example, a Ti / Al / Pt / Au electrode structure, and is electrically connected to a silicon-doped GaN layer 74 that is a first conductivity type semiconductor layer via a base 71.
[0064]
In the semiconductor laser device of the present embodiment having the structure shown in FIG. 10, p-side electrode layers 84 and 85 are formed in two crystal planes that are inclined with respect to the main surface of the substrate and are provided on both sides of the ridgeline. When the electrode layers 84 and 85 are formed using photolithography or the like, the distance between the electrodes can be secured, which is advantageous when fine processing is performed. In addition, since the narrow openings 86 and 87 formed in the insulating film 81 function as current confinement portions, a laser element can be formed while suppressing variations in emission wavelength, and the emission wavelength is stable. Semiconductor laser elements can be manufactured with good reproducibility.
[0065]
In addition, it has an element structure in which the emission wavelengths can be controlled to a plurality by changing the height of the openings 86 and 87 so that one is high and the other is low. It is also possible to form a plurality of pieces such as two on both sides of the crystal plane inclined with the ridge line in between.
[0066]
[Fourth Embodiment]
FIG. 11 shows a cross-sectional view of the element structure of the semiconductor laser element of the fourth embodiment. This embodiment is an example in which a magnesium-doped GaN layer is formed on each of two inclined surfaces facing each other across a ridgeline.
[0067]
A selection mask 92 made of, for example, a silicon oxide film is formed on a base 91 that is a laminate of a sapphire substrate and an underlying growth layer with the substrate main surface. The base 91 is a structure in which, for example, an undoped GaN layer and a silicon-doped GaN layer are stacked on a sapphire substrate whose main surface is a C-plane. An AlN layer or the like may be formed as the buffer layer. In the selection mask 92, an opening 93 having a stripe shape is formed by hydrofluoric acid etching after forming a resist mask. Also in this embodiment, the longitudinal direction of the opening 93 is set to, for example, the [1-100] direction or the [11-20] direction in order to obtain crystal growth having a ridge line, as in the above-described embodiment.
[0068]
From the elongated strip-shaped opening 93, a silicon-doped GaN layer 94 is formed as a first conductivity type semiconductor layer by selective growth. Also in this embodiment, the silicon-doped GaN layer 94 has a substantially triangular cross section and grows from an elongated strip-shaped opening 93, so that the direction perpendicular to the cross section shown in the drawing is the longitudinal direction. To do. Resonant surfaces are formed by cleavage or etching at both ends of the longitudinal direction (not shown), and laser oscillation is possible. In the silicon-doped GaN layer 94, the plane constituted by the hypotenuse having a substantially triangular cross section is a crystal plane inclined with respect to the main surface of the substrate. During the growth of the silicon-doped GaN layer 94, the growth temperature is set to 980 ° C., for example.
[0069]
On the silicon-doped GaN layer 94, In _0.05 Ga _0.95 The N layer 95 is formed as a guide layer with a film thickness of 10 nm, for example. _0.05 Ga _0.95 On the N layer 95, In is used as an active layer. _0.2 Ga _0.8 The N layer 96 is formed with a film thickness of 3 nm, for example, and the In layer _0.2 Ga _0.8 On the N layer 96, as a guide layer, In _0.05 Ga _0.95 The N layer 97 is formed with a film thickness of 10 nm, for example. These In _0.05 Ga _0.95 N layer 95, In _0.2 Ga _0.8 N layer 96 and In _0.05 Ga _0.95 The N layer 97 is formed so as to be laminated on the inclined surfaces on both sides across the ridge line of the silicon-doped GaN layer 94 corresponding to the apex having a substantially triangular cross section.
[0070]
In as a guide layer _0.05 Ga _0.95 On the N layer 97, a magnesium-doped GaN layer 98 is formed as a second conductivity type semiconductor layer, but in this embodiment, the magnesium-doped GaN is so coated as to cover only a part of the inclined surface rather than the entire area. Layer 98 is formed. In _0.05 Ga _0.95 In a region where the magnesium-doped GaN layer 98 is not formed on the N layer 97, an insulating film 99 such as a silicon oxide film is formed. The insulating film 99 is formed so as to cover a semiconductor layer having a triangular cross section with a portion other than the magnesium-doped GaN layer 98. Here, the width on the slope of the magnesium-doped GaN layer 98 is set to be thin, for example, about 1 to 3 μm. For example, the magnesium-doped GaN layer 98 is formed into a thin strip pattern by etching or the like.
[0071]
A p-side electrode layer 100 is formed on the magnesium-doped GaN layer 98 and the insulating film 99. The p-side electrode layer 100 has a laminated structure of, for example, Ni / Pt / Au or Ni (Pd) / Pt / Au. The p-side electrode layer 100 is formed on the entire surface, and is formed so as to be electrically connected to at least the magnesium-doped GaN layer 98 by a technique such as etching or lift-off. As described above, the magnesium-doped GaN layer 98 is already formed in a thin band shape of about 1 to 3 μm, for example, so that the p-side electrode layer 100 can be formed in a relatively wide area.
[0072]
An n-side electrode layer 102 is formed in the opening 103 where the selection mask 92 and the insulating film 104 are opened, beside the semiconductor layer having a triangular cross section. The n-side electrode layer 102 has, for example, a Ti / Al / Pt / Au electrode structure, and is electrically connected to a silicon-doped GaN layer 94 that is a first conductivity type semiconductor layer via a base 91.
[0073]
In the semiconductor laser device of the present embodiment having the structure shown in FIG. 11, a magnesium-doped GaN layer 98 having a thin line width is formed in each of two crystal planes that are inclined with respect to the main surface of the substrate and are provided on both sides of the ridgeline, Since the insulating film 99 is formed so as to fill the periphery of the magnesium-doped GaN layer 98, even if the p-side electrode layer 100 is formed in a relatively wide region, a partial region that should emit light reliably is formed. In addition, when the p-side electrode layer 100 is formed using photolithography or the like, fine processing becomes easy. In addition, since the narrow magnesium-doped GaN layer 98 formed between the insulating films 99 functions as a current confinement portion, it is possible to form a laser element while suppressing variations in emission wavelength. A semiconductor laser element having a stable wavelength can be manufactured with good reproducibility.
[0074]
In this embodiment, the magnesium-doped GaN layer 98 is formed on the inclined surfaces on both sides of the ridgeline, but it can also be formed on one inclined surface. It is also possible to form a plurality of magnesium-doped GaN layers 98 in each inclined plane.
[0075]
[Fifth Embodiment]
FIG. 12 is a cross-sectional view of the element structure of the semiconductor laser element of the fifth embodiment. This embodiment is an example in which an active layer having a thin line width is formed on each of two inclined surfaces facing each other across a ridge line.
[0076]
A selection mask 112 made of, for example, a silicon oxide film is formed on a substrate 111 that is a laminate of a sapphire substrate and a base growth layer with the substrate main surface. The base 111 is a structure in which, for example, an undoped GaN layer and a silicon-doped GaN layer are stacked on a sapphire substrate whose main surface is a C-plane. An AlN layer or the like may be formed as the buffer layer. In the selection mask 112, openings 113 having openings in a stripe shape are formed by hydrofluoric acid etching after forming a resist mask. Also in this embodiment, the longitudinal direction of the opening 113 is set to, for example, the [1-100] direction or the [11-20] direction in order to obtain crystal growth having a ridge line, as in the above-described embodiment.
[0077]
From the elongated strip-shaped opening 113, a silicon-doped GaN layer 114 is formed as a first conductivity type semiconductor layer by selective growth. Also in this embodiment, the silicon-doped GaN layer 114 has a substantially triangular shape in cross section and grows from an elongated strip-shaped opening 113, so that the direction perpendicular to the cross section is the longitudinal direction. Resonant surfaces are formed by cleavage or etching at both ends of the longitudinal direction (not shown), and laser oscillation is possible. In the silicon-doped GaN layer 114, the plane formed by the hypotenuse having a substantially triangular cross section is a crystal plane inclined with respect to the main surface of the substrate. During the growth of the silicon-doped GaN layer 114, the growth temperature is set to 980 ° C., for example.
[0078]
On the silicon-doped GaN layer 114, In _0.05 Ga _0.95 The N layer 115 is formed as a guide layer with a film thickness of 10 nm, for example. _0.05 Ga _0.95 On the N layer 115, In is used as an active layer. _0.2 Ga _0.8 The N layer 116 is formed with a film thickness of 3 nm, for example. In this embodiment, In _0.2 Ga _0.8 The N layer 116 is formed in a thin strip pattern, and a low conductive layer 117 having a low conductivity such as an undoped GaN layer is formed in the upper and lower regions. An insulating layer can be formed instead of the low conductive layer 117.
[0079]
Low conductive layer 117 and In _0.2 Ga _0.8 On the N layer 116, In is used as a guide layer. _0.05 Ga _0.95 The N layer 118 is formed with a thickness of 10 nm, for example. This In _0.05 Ga _0.95 A magnesium-doped GaN layer 119 is formed on the N layer 118 as a second conductivity type semiconductor layer, and a p-side electrode layer 120 is formed on the magnesium-doped GaN layer 119. The p-side electrode layer 120 has a laminated structure of, for example, Ni / Pt / Au or Ni (Pd) / Pt / Au. In which becomes the active layer _0.2 Ga _0.8 Since the N layer 116 is already formed in a thin band shape as described above, the p-side electrode layer 120 can be formed in a relatively wide region.
[0080]
An n-side electrode layer 122 is formed in the opening 123 where the selection mask 112 and the insulating film 124 are opened beside the semiconductor layer having a triangular cross section. The n-side electrode layer 122 has a Ti / Al / Pt / Au electrode structure, for example, and is electrically connected to the silicon-doped GaN layer 114 serving as the first conductivity type semiconductor layer via the base 111.
[0081]
In the semiconductor laser device of the present embodiment having the structure shown in FIG. 12, an In layer which is an active layer having a thin line width in each of two crystal planes inclined with respect to the main surface of the substrate and provided on both sides of the ridgeline. _0.2 Ga _0.8 The N layer 116 is formed, and even if the p-side electrode layer 120 is formed in a relatively wide area, a partial region that should emit light can be surely formed, and the p-side electrode layer 120 can be formed using photolithography or the like. When forming, fine processing can be easily performed. Further, a narrow In width formed between the low conductive layers 117. _0.2 Ga _0.8 Since the N layer 116 functions as an active layer, a laser element can be formed while suppressing variations in emission wavelength, and a semiconductor laser element having a stable emission wavelength can be manufactured with good reproducibility.
[0082]
In this embodiment, In _0.2 Ga _0.8 Although the N layer 116 is formed on the inclined surfaces on both sides of the ridgeline, it can be formed on one inclined surface. In addition, a plurality of Ins in each inclined surface _0.2 Ga _0.8 The N layer 116 may be formed.
[0083]
[Sixth Embodiment]
FIG. 13 is a cross-sectional view of the main part of the gallium nitride compound semiconductor laser device of this embodiment. A selection mask 132 made of, for example, a silicon oxide film is formed on a base 131 that is a laminate of a sapphire substrate and an underlying growth layer with the substrate main surface. Specifically, the base 131 is a structure in which, for example, an undoped GaN layer and a silicon-doped GaN layer are stacked on a sapphire substrate whose principal surface is a C-plane. An AlN layer or the like may be formed as the buffer layer. In the selection mask 132, an opening 133 having a stripe shape is formed by hydrofluoric acid etching after forming a resist mask. In the present embodiment, the longitudinal direction of the opening 133 is the [1-100] direction or the [11-20] direction in order to achieve crystal growth with a ridge line.
[0084]
From the elongated strip-shaped opening 133, a silicon-doped GaN layer 134 is formed as a first conductivity type semiconductor layer by selective growth. In the present embodiment, the silicon-doped GaN layer 134 has a substantially trapezoidal cross section, and in order to grow from the elongated strip-shaped opening 133, the direction perpendicular to the illustrated cross section is the longitudinal direction. In the silicon-doped GaN layer 134 having a substantially trapezoidal cross section, the flat upper surface is, for example, the C plane, and the inclined surfaces on both sides are, for example, the S plane. Resonant surfaces are formed by cleavage or etching at both ends of the longitudinal direction (not shown), and laser oscillation is possible. In the silicon-doped GaN layer 134, the plane formed by the hypotenuse having a substantially trapezoidal cross section is a crystal plane inclined with respect to the main surface of the substrate. During the growth of the silicon-doped GaN layer 134, the growth temperature is set to 980 ° C., for example.
[0085]
On the silicon-doped GaN layer 134, In _0.05 Ga _0.95 The N layer 135 is formed as a guide layer with a film thickness of 10 nm, for example. _0.05 Ga _0.95 On the N layer 135, In is used as an active layer. _0.2 Ga _0.8 The N layer 136 is formed with a film thickness of 3 nm, for example, and the In layer _0.2 Ga _0.8 On the N layer 136, In is used as a guide layer. _0.05 Ga _0.95 The N layer 137 is formed with a film thickness of 10 nm, for example. These In _0.05 Ga _0.95 N layer 135, In _0.2 Ga _0.8 N layer 136 and In _0.05 Ga _0.95 The N layer 137 is formed so as to be laminated on the inclined surfaces on both sides of the silicon-doped GaN layer 134 corresponding to the apex of the substantially trapezoidal cross section and the upper surface parallel to the main surface of the substrate.
[0086]
In as a guide layer _0.05 Ga _0.95 On the N layer 137, a magnesium-doped GaN layer 138 is formed as a second conductivity type semiconductor layer. The magnesium-doped GaN layer 138 is a layer that functions as a second conductivity type semiconductor layer, and is a p-type compound semiconductor layer. An insulating film 139 such as a silicon oxide film is formed on the magnesium-doped GaN layer 138. The insulating film 139 is formed so as to cover the semiconductor layer having a trapezoidal cross section, and an opening 140 is formed by opening a part on the inclined surface of the insulating film 139. The opening 140 extends in the horizontal direction, and faces the semiconductor layer at a height where the opening 140 exists. The width on the slope of the opening 140 is set to be narrow, for example, about 1 to 3 μm.
[0087]
A p-side electrode layer 141 is formed in the region where the opening 140 is formed. The p-side electrode layer 141 has a laminated structure of, for example, Ni / Pt / Au or Ni (Pd) / Pt / Au. The p-side electrode layer 141 is formed on the entire surface, and then formed into a thin strip pattern by a technique such as etching or lift-off. The p-side electrode layer 141 partially formed on this inclined surface is deposited on the interface of the magnesium-doped GaN layer 138 through the opening 140 narrowed to about 1 to 3 μm, for example, as described above. A current is intensively supplied to a predetermined height of the trapezoidal semiconductor layer so that a region to emit light is a partial region limited in the width direction of the slope.
[0088]
A selection mask 132 and an insulating film 139 are opened beside the semiconductor layer having a trapezoidal cross section to form an n-side electrode layer 142. The n-side electrode layer 142 has, for example, a Ti / Al / Pt / Au electrode structure, and is electrically connected to the silicon-doped GaN layer 134 that is the first conductivity type semiconductor layer via the base 131.
[0089]
In such a semiconductor laser element, since the narrow opening 140 formed in the insulating film 139 functions as a current constriction part, the laser element can be formed while suppressing variations in emission wavelength, and light emission It is possible to manufacture a semiconductor laser element having a stable wavelength with good reproducibility. The p-side electrode layer 141 can be additionally formed on the other inclined surface, and a plurality of electrode layers can be provided on each inclined surface having the trapezoidal cross section. In these embodiments, the electrode portion is partially thermally activated (a mask is formed and only the mask opening is activated), or hydrogen ions are implanted in a portion other than the stripe portion so that a current flows only in the stripe. Thus, a current injection portion can be formed.
[0090]
【The invention's effect】
According to the semiconductor laser device of the present invention, since the narrow electrode layer, semiconductor layer, active layer, etc. function as a partial region on the crystal plane inclined with respect to the main surface of the substrate, each of the emission wavelengths varies. Thus, a laser element can be formed while being suppressed, and a semiconductor laser element having a stable emission wavelength can be manufactured with good reproducibility. Further, according to the semiconductor laser device of the present invention, since the crystal plane inclined with respect to the main surface of the substrate is used for light emission, the current density can be increased while suppressing crystal dislocation, and a semiconductor laser device having high luminance can be obtained. Can be manufactured.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an element structure of a semiconductor laser element according to a first embodiment of the present invention.
FIG. 2 is a schematic diagram for explaining a partial region of the semiconductor laser device according to the first embodiment of the present invention.
FIG. 3 is a process perspective sectional view in the method of manufacturing a semiconductor laser device according to the first embodiment of the present invention, and is a process perspective sectional view up to an opening forming process.
FIG. 4 is a process perspective sectional view in the method of manufacturing a semiconductor laser device according to the first embodiment of the present invention, and is a process perspective sectional view up to a process of forming a silicon-doped GaN layer.
5 is a process perspective sectional view in the method of manufacturing a semiconductor laser device according to the first embodiment of the present invention, and is a sectional view taken along line VV in FIG. 4 and to a process of forming a silicon-doped GaN layer; FIG. FIG.
FIG. 6 is a process perspective sectional view in the method of manufacturing a semiconductor laser device according to the first embodiment of the present invention, and is a process perspective sectional view up to a process of forming a magnesium-doped GaN layer.
FIG. 7 is a process perspective sectional view in the method of manufacturing a semiconductor laser device according to the first embodiment of the present invention, and is a process perspective sectional view up to an opening forming process.
FIG. 8 is a process perspective sectional view in the method of manufacturing a semiconductor laser device according to the first embodiment of the present invention, and is a process perspective sectional view up to a p-side electrode layer forming process.
FIG. 9 is a sectional view showing an element structure of a semiconductor laser element according to a second embodiment of the present invention.
FIG. 10 is a cross-sectional view showing an element structure of a semiconductor laser element according to a third embodiment of the present invention.
FIG. 11 is a sectional view showing an element structure of a semiconductor laser element according to a fourth embodiment of the present invention.
FIG. 12 is a sectional view showing an element structure of a semiconductor laser element according to a fifth embodiment of the present invention.
FIG. 13 is a sectional view showing an element structure of a semiconductor laser element according to a sixth embodiment of the present invention.
FIG. 14 is a characteristic diagram showing the relationship between the wavelength and the length from the bottom of the semiconductor laser device according to the present invention.
[Explanation of symbols]
11, 31, 51, 71, 91, 111, 131 substrate
12, 32, 52, 72, 92, 112, 132 Selection mask
13, 33, 53, 73, 93, 113, 133 Opening
14, 34, 54, 74, 94, 114, 134 Silicon-doped GaN layer
15, 35, 55, 75, 95, 115, 135 In _0.05 Ga _0.95 N layers
16, 36, 56, 76, 96, 116, 136 In _0.2 Ga _0.8 N layers
17, 37, 57, 77, 97, 118, 137 In _0.05 Ga _0.95 N layers
18, 38, 58, 78, 98, 119, 138 Magnesium-doped GaN layer
19, 41, 64, 65, 84, 85, 100, 120, 141 p-side electrode layer
22, 42, 62, 82, 102, 122, 142 n-side electrode layer

Claims (16)

Look clamping an active layer is extended along a crystal plane inclined to the substrate main surface in the first conductivity type semiconductor layer and the second conductive type semiconductor layer,
The active layer, the first conductive semiconductor layer, and the second conductive semiconductor layer have a structure formed in a substantially triangular shape in a cross section substantially perpendicular to the crystal plane,
An end surface substantially perpendicular to the crystal plane is a resonance surface,
Ri partial region der in the light emitting region is inclined in the active layer surface,
The semiconductor laser device, wherein the crystal plane inclined with respect to the main surface of the substrate is formed by selective growth from the substrate . 2. The semiconductor laser device according to claim 1, wherein the width in the in-plane direction of the partial region is set in a range in which a variation in emission wavelength of the semiconductor laser device is 10 nm or less. 2. The semiconductor laser device according to claim 1, wherein the partial region has a width of 3 [ mu] m or less in the in-plane direction.   2. The semiconductor laser device according to claim 1, wherein the partial region is formed by forming an electrode for supplying a current to the active layer so as to have a predetermined width in a direction within an inclined plane. 5. The semiconductor laser device according to claim 4, wherein the electrode is formed in a portion where an insulating film is opened in a stripe shape.   The partial region is configured by forming at least one of the first conductive type semiconductor layer and the second conductive type semiconductor layer sandwiching the active layer so as to have a predetermined width in a direction within an inclined plane. The semiconductor laser device according to claim 1.   2. The semiconductor laser device according to claim 1, wherein the partial region is formed by forming the active layer so as to have a predetermined width in the direction of inclination in the inclined plane.   2. The semiconductor laser device according to claim 1, wherein the partial region is formed at one place in a direction within an inclined plane.   2. The semiconductor laser device according to claim 1, wherein the partial region is formed at a plurality of locations in a direction within an inclined plane. The semiconductor laser device according to claim 1, characterized in that the partial region is formed on one of the inclined surfaces of the substantially triangular shape. The semiconductor laser device according to claim 1, characterized in that the partial region is formed on the inclined surface of both of said substantially triangular. An active layer extending along a crystal plane inclined with respect to the main surface of the substrate is sandwiched between the first conductive type semiconductor layer and the second conductive type semiconductor layer,
The active layer, the first conductive semiconductor layer, and the second conductive semiconductor layer have a structure formed in a substantially trapezoidal shape in a cross section substantially perpendicular to the crystal plane,
An end surface substantially perpendicular to the crystal plane is a resonance surface,
Ri partial region der in the light emitting region is inclined in the active layer surface,
The semiconductor laser device, wherein the crystal plane inclined with respect to the main surface of the substrate is formed by selective growth from the substrate . Have a crystal plane tilted from the principal surface of the substrate by selective growth on a substrate to form a first conductivity type semiconductor layer having a structure in which a substantially triangular shape or a substantially trapezoidal shape in cross section substantially perpendicular to the crystal plane Process,
Forming an active layer on the first conductive semiconductor layer;
Forming a second conductivity type semiconductor layer on the active layer;
Forming an electrode layer in contact with the second conductivity type semiconductor layer at a part of an inclined surface on the second conductivity type semiconductor layer. A method for manufacturing a semiconductor laser device, comprising: 14. The method of manufacturing a semiconductor laser device according to claim 13 , further comprising a step of forming an insulating film opened in the part before forming the electrode layer. 14. The method of manufacturing a semiconductor laser device according to claim 13, wherein the electrode layer is formed on the entire surface and then removed except for a region that is partially in contact with the second conductive semiconductor layer. 14. The method of manufacturing a semiconductor laser device according to claim 13, wherein the second conductive semiconductor layer is formed on the entire surface and then removed except for a region that is partially in contact with the electrode layer.

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