JP2002246697A - Semiconductor laser element and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser element which can reduce the occurrence of a crack and has a excellent photoelectric characteristics. SOLUTION: The semiconductor laser element comprises a substrate 1 and an n-GaN layer 102 which is formed on the substrate 1 and consists of a nitride semiconductor. The substrate 1 comprises a groove having a surface tilted at 62 deg. from the major surface of the substrate or a surface tilted from the surface by 3 deg. or less in an arbitrary direction as a slope. The n-GaN layer 102 is formed on the slope and has a lower clad layer 103, an active layer 105, and an upper clad layer 108 consisting of nitride semiconductors thereon. Further, the active layer 105 has a plane orientation substantially conforming to the major surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor laser device using a nitride semiconductor and a method for manufacturing the same.

[0002]

2. Description of the Related Art A nitride semiconductor material composed of GaN, InN, AlN and a mixed crystal semiconductor thereof has been used to form In _x Ga _1- on a sapphire substrate, a GaN substrate, a SiC substrate or a silicon (111) substrate. A light-emitting element using an _xN crystal as a light-emitting layer has been manufactured.

In particular, since a silicon substrate having a large area and a constant quality can be obtained at a low cost as compared with other substrates, it is expected that the light emitting element can be manufactured at low cost by adopting the silicon substrate. Have been. Also, trial production of a semiconductor laser device has been attempted using a nitride semiconductor material composed of these mixed crystal semiconductors.

[0004]

However, silicon (1)
11) When a nitride semiconductor is grown using a substrate, a nitride semiconductor film having a C-plane as a growth surface is obtained.
This epitaxial semiconductor film was not very flat at the atomic level.

For example, an n-type cladding layer, a quantum well type light emitting layer made of In _x Ga ₁ -xN, and a p-type cladding layer are laminated on these substrates to produce an LD (laser diode) having a fine structure. In this case, due to the effect of the unevenness of the film,
Since the thickness and the In composition of the light emitting layer become non-uniform, the light emission is affected. Therefore, it has an emission spectrum with a wide half-value width of 40 nm, so that it is difficult to obtain stimulated emission light,
Therefore, it is difficult to obtain only a semiconductor laser device having a high oscillation threshold, and only an inferior device as compared with a device on a sapphire substrate or a SiC substrate has been obtained. Therefore, it has been difficult to obtain a semiconductor laser device having a small driving current.

A problem with lasers using a nitride semiconductor material is that if an Al-containing nitride semiconductor material having a large energy gap is not used in both the cladding layers formed above and below the active layer, the active layer will It has been found that it is impossible to manufacture a semiconductor laser device having a low driving current by sufficiently confining light and electrons to emit light with high efficiency.

However, the nitride semiconductor material containing Al has a problem that cracks are likely to occur as the crystal grows. In order to improve the initial characteristics such as the threshold value of the semiconductor laser and prevent the life of the semiconductor layer from deteriorating, the active layer of the nitride semiconductor material has a problem. When a nitride semiconductor material containing Al is used for both the upper and lower clad layers, it has been required to prevent the occurrence of cracks. In particular, when a silicon substrate is used,
Silicon has a smaller coefficient of thermal expansion than nitride semiconductors, and thus, when grown and returned to room temperature, the grown nitride semiconductors are subjected to tensile stress, so cracks are much more likely to occur than sapphire substrates and the like There was a problem.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a semiconductor laser device which suppresses generation of cracks and has excellent photoelectric characteristics and a method for manufacturing the same.

[0009]

According to one aspect, a semiconductor laser device according to the present invention has a substrate and a compound semiconductor layer formed of a nitride semiconductor formed on the substrate.
The substrate includes a groove having a surface inclined at 62 degrees from the main surface of the substrate or a surface inclined within 3 degrees in an arbitrary direction from the surface as a slope, and the compound semiconductor layer is provided on the slope. Formed on the compound semiconductor layer, a lower cladding layer each composed of a nitride semiconductor, an active layer,
The active layer has an upper clad layer, and the active layer has a plane orientation substantially coincident with the main surface.

In another aspect, a semiconductor laser device according to the present invention includes a substrate and a compound semiconductor layer formed of a nitride semiconductor formed on the substrate, wherein the substrate has a main surface of the substrate. A groove having a surface inclined at an angle of 62 degrees or a surface inclined within 3 degrees in an arbitrary direction from the surface as a slope, the compound semiconductor layer is formed on the slope and the compound semiconductor layer is formed on the surface; A lower clad layer composed of a nitride semiconductor, an active layer composed of a nitride semiconductor, and an upper clad layer are formed thereon, and the lower clad layer and the upper clad layer are composed of a nitride semiconductor containing Al. It is characterized by being performed.

Preferably, the substrate is made of silicon. In still another aspect, a semiconductor laser device according to the present invention has a silicon substrate and a compound semiconductor layer formed of a nitride semiconductor formed on the silicon substrate. A groove having a surface inclined at an angle of 62 degrees from the surface or a surface inclined within 3 degrees in an arbitrary direction from this surface as an inclined surface, and the compound semiconductor layer is formed on the inclined surface and nitrided. A lower cladding layer, an active layer, and an upper cladding layer composed of a semiconductor.

In still another aspect, a semiconductor laser device according to the present invention has a silicon substrate and a compound semiconductor layer formed of a nitride semiconductor formed on the silicon substrate. The (100) plane is [01-1]
It is formed using a silicon substrate having a main surface composed of a plane rotated by 7.3 degrees around the axis or a plane inclined within 3 degrees in an arbitrary direction from this plane, and the silicon substrate is formed of (111) A compound semiconductor layer is formed on the slope, and has a lower cladding layer, an active layer, and an upper cladding layer each formed of a nitride semiconductor.

The upper clad layer and the lower clad layer are
Preferably, it is composed of a nitride semiconductor containing Al. Further, the active layer may have a plane orientation substantially coincident with the main surface of the substrate.

[0014] Further, the compound semiconductor layer has a <0001
The> direction may be substantially perpendicular to the slope. Further, the active layer may have a (1-101) plane as a plane orientation.

The groove may extend in the [11-20] direction of the nitride semiconductor constituting the active layer. Further, a waveguide stripe structure of laser light may be formed along the groove.

[0016] A film may be formed on at least a part of the surface of the substrate other than the inclined surface so as to suppress the growth of the nitride semiconductor.

In one aspect, a method of manufacturing a semiconductor laser device according to the present invention includes the steps of: providing, on a main surface of a substrate, a surface inclined at 62 degrees from the main surface or within 3 degrees in an arbitrary direction from the main surface; Forming a groove having a surface inclined as a slope as a slope, crystal growing a nitride semiconductor on the slope to form a compound semiconductor layer, and forming the compound semiconductor layer on the compound semiconductor layer;
Sequentially stacking a lower cladding layer, an active layer, and an upper cladding layer each formed of a nitride semiconductor.

In another aspect of the method of manufacturing a semiconductor laser device according to the present invention, the (100) plane is rotated by 7.3 degrees around the [01-1] axis or from the plane in any direction. Forming a groove having a (111) plane as a slope on a main surface of a silicon substrate having a main surface constituted by a plane inclined within a degree, and crystal-growing a nitride semiconductor on the slope. Forming a compound semiconductor layer, and sequentially laminating a lower clad layer, an active layer, and an upper clad layer each composed of a nitride semiconductor on the compound semiconductor layer.

The method for manufacturing a semiconductor laser device includes a step of forming a film on which growth of a nitride semiconductor is suppressed on at least a part of the surface of the substrate other than the slope before forming the compound semiconductor layer. It may be.

The plurality of grooves are provided on the substrate. In this case, in the method of manufacturing a semiconductor laser device described above, the compound semiconductor layers formed on the slopes of the grooves are united according to crystal growth.

After the compound semiconductor layer is formed, a step of removing the substrate may be provided. Preferably, the crystal is grown so that the <0001> direction of the compound semiconductor layer is substantially perpendicular to the slope. Further, the upper clad layer and the lower clad layer may be formed of a nitride semiconductor containing Al.

Preferably, the active layer is grown so as to have a plane orientation substantially coincident with the main surface of the substrate. Further, the active layer preferably has a (1-101) plane as a plane orientation.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

<First Embodiment> FIG. 1 is a conceptual diagram for forming a (1-101) facet surface 70 of a nitride semiconductor film according to the present embodiment, and FIG. 2 is a nitride semiconductor according to the present embodiment. FIG. 3 is a schematic cross-sectional view illustrating a structure of a laser element.

The nitride semiconductor laser device of the present embodiment is formed on a 7.3 degree (001) Si off substrate 1 in the [0-1-1] direction. The substrate 1 has a stripe-shaped groove having an inclined surface at an angle of 62 degrees from its main surface 60 as a (111) facet surface 61, and is sequentially flattened from the facet surface 61 as described below. It has an n-AlGaInN layer 10 and an n-GaN layer 102 that are stacked one upon another.

The upper surface of the n-GaN layer 102 is substantially parallel to the main surface of the substrate and is a (1-101) plane. On top of this, n-Al _X1 Ga _1-X1 N (X1 = 0.1) lower cladding layer 103 (1.2 μm in thickness), n-GaN lower guide layer 104 (0.1 μm in thickness), and In _W Ga _1-W N
(0 <W <1) well layer and In _V Ga _{1 -V} N (0 ≦ V <W)
Triple quantum well active layer 1 having an alternate multilayer structure with a barrier layer
05 (emission wavelength 400 nm, total film thickness 40 nm), AlG
aN cap layer 106 (20 nm thick), p-GaN upper guide layer 107 (0.1 μm thick), p-Al _X2 Ga
_1-X2 N (X2 = 0.1) cladding layer 108 (film thickness 0.4
_{μm), p-Al a In} b Ga 1-ab N (a = 0, b =
0.1) Each nitride semiconductor layer of the contact layer 109 (having a thickness of 0.03 μm) is formed.

Furthermore, on the upper surface of the _{p-Al a In b Ga 1} -ab N contact layer 109, a metal electrode 110 is formed, the back surface of the silicon substrate metal electrode 111 is formed. Part of p-cladding layer 108 and p-Al _a I
The n _b Ga _1-ab N contact layer 109 is formed in a ridge stripe shape, and forms a lateral light confinement structure of the semiconductor laser.

As shown in FIG. 2, in the semiconductor laser of this embodiment, the metal electrodes 110 are formed in a stripe shape.
The metal electrode 110 is in contact with the semiconductor layer only in the ridge stripe portion, and the semiconductor layer (p clad layer 10
8), and may extend to portions other than the ridge stripe portion with an insulating film interposed therebetween. Again,
The current flows only through the ridge stripe,
A current confinement structure can be realized.

As a dopant for forming the n-type semiconductor, Si, Ge, O, S, Se is preferably used. In addition, Be, Cd, and Mg are preferably used as a dopant for forming a p-type semiconductor. B
Addition of any of Si, Ge, O, S, and Se simultaneously with e, Cd, and Mg was also effective for obtaining a p-type layer having low resistance and low dopant diffusion.

Next, a method of manufacturing the semiconductor laser device according to the present embodiment will be described with reference to FIGS.

First, the (001) silicon substrate which has been turned off by 7.3 degrees in the [0-1-1] direction is cleaned, and sputtering or CVD (Chemical Vapor Depositio) is performed thereon.
n) Using a technique, a silicon oxide film or a silicon nitride film 52 is deposited to a thickness of 100 nm. Thereafter, as shown in FIG. 4, the silicon oxide film or the silicon nitride film 52 is removed in a stripe shape by performing photolithography. At this time, the direction of the stripe is Si [01-
1] direction.

Further, a groove having a Si (111) facet surface 61 as shown in FIG. 5 is formed on the wafer by an alkali etchant such as KOH or an acid etchant such as buffered hydrofluoric acid. This groove is formed by Si [0
1-1] are stripe-shaped grooves extending in the direction. Figure 1
As shown in (1), the (111) facet surface 61 had a relationship of 62 degrees with the main surface 60 of the silicon substrate. This surface is a flat facet surface obtained by the above-described etching, and can be easily formed by appropriately adjusting the temperature of the etchant and the etching rate.

At this time, the groove itself has a V-shape or a substantially V-shape having a flat bottom, and the other slope is a (1-1-1) facet surface. Since the silicon substrate is an off-substrate, the V-shape is not symmetrical. Therefore, the (111) slope is a plane inclined at about 62 degrees with respect to the substrate main surface, while the (1-1-1) slope is a plane inclined at about 47 degrees with respect to the substrate main surface.

The substrate is tilted in the sputtering apparatus to form a film on the (111) facet surface 61 so that the film is not formed on the (111) facet surface 61. As shown in FIG.
(1-1-1) A mask 52 made of a silicon oxide film or a silicon nitride film is formed so as to cover the facet surface. This is used as a substrate for producing a nitride semiconductor substrate. FIG. 8 shows the orientation relationship between the silicon substrate and the facet surface and the like at this time.

Then, a nitride semiconductor film is grown by MOCVD (metal organic chemical vapor deposition) under the following growth conditions.

On the facet surface 61 of the silicon substrate having undergone the above process, the n-AlGaInN intermediate layers 10 and n
-A GaN crystal film having a flat GaN (1-101) surface on the upper surface through a growth process as shown in FIGS. 7A and 7B by growing the crystal of the GaN layer 102 (compound semiconductor layer). Can be produced. Here, the intermediate layer 10 is a thin film having a thickness of about 100 nm or less, which plays a role as a buffer layer.

Crystal growth starts on the exposed (111) facet plane. Specifically, as shown in FIGS. 7A and 7B, the growing nitride semiconductor is oriented so that the <0001> direction is perpendicular to the slope. On the upper surface of the grown crystal, GaN (1-10
1) The surface 70 appears, and during the growth stage, it becomes a crystal having a shape like a triangular prism extending in a stripe shape.

FIG. 3 shows the growth direction of the nitride semiconductor. In FIG. 3, 80 indicates the c-axis of the nitride semiconductor, and 81 indicates the growth progress direction of the nitride semiconductor. Similar results were obtained even when an AlInN intermediate layer, an AlGaN intermediate layer, and an AlN intermediate layer were used as the intermediate layers used in the initial stage of growth.

When a silicon substrate is used, the nitride semiconductor film is liable to undergo c-axis oriented crystal growth on the substrate. However, in the present invention, the relationship between the facet and the off-angle of the substrate is six.
By using a substrate formed twice, a crystal film having a flat (1-101) facet plane of a nitride semiconductor can be used.

Subsequently, n-Al _X1 Ga _1-X1 N (X1 =
0.1) Lower clad layer 103, n-GaN lower guide layer 104, In _W Ga _{1 -W} N (0 <W <1) well layer and In
_A triple quantum well active layer 105, an AlGaN cap layer 106, a p-GaN upper guide layer 107, and a p-Al _X2 G having an alternate multilayer structure with a _V Ga _{1 -V} N (0 ≦ V <W) barrier layer.
a _1-X2 N (X2 = 0.1) cladding layer 108, p-Al
By _a an In _b a _{Ga 1-ab N (a =} 0, b = 0.1) contact layer 109, MOCVD (metal organic chemical vapor deposition) method, are sequentially stacked.

Thereafter, p-Al _X2 G
a _1-X2 N (X2 = 0.1) cladding layer 108, p-Al
_The element structure shown in FIG. 2 is manufactured by removing the _a- In _b Ga _1-ab N (a = 0, b = 0.1) contact layer 109 except for a stripe-shaped portion having a width of 2 μm.

Thereafter, a mask is partially formed on the epitaxial film formed by the above selective growth technique,
The mirror end face is formed by using an etching technique such as BE (reactive ion beam etching). The mirror end face may be formed by a cleavage technique.

[0043] upper surface of _{p-Al a In b Ga 1} -ab N contact layer 109, a metal electrode 110. Pd / Au, Ni / Pd / Au, Pd
/ Pt / Au, Pd / Mo / Au, Pd / W / Au may be used, and the total thickness may be about 0.05 to 3 μm. After that, a metal electrode 111 is formed on the back surface of the substrate. As the metal electrode 111, Ti / Al, Zr
/ Al, Hf / Al or W / Al may be used, and the total thickness may be about 0.05 to 3 μm.

Further, by covering the metal electrode 111, Mo /
A stacked structure of Au, Mo / Ni, W / Au, Cr / Ni, or the like may be formed so that wire bonding or die bonding can be easily performed.

The silicon substrate used here is (001)
It has a main surface 60 tilted 7.3 degrees [0-1-1] from the plane, that is, rotated 7.3 degrees around the [01-1] axis from the (001) plane. The active layer has (1-101) as a plane orientation, and this can have substantially the same plane orientation as the main surface 60 of the silicon substrate. When the surface was tilted in any direction within 3 degrees from this surface, an extremely flat nitride semiconductor interface having a plane orientation close to the (1-101) plane was obtained.

In this embodiment, the nitride semiconductor film is grown only on the trench as shown in FIG.
101) By forming a laser structure continuously on the facet surface 70, as shown in FIG. 2, semiconductor light emitting devices separated into individual triangular prism-shaped crystals are separately formed, and the semiconductor laser devices are individually formed. It is to be produced.

When the characteristics of the manufactured semiconductor device were measured, a semiconductor laser device having an extremely low oscillation threshold of 15 mA was obtained. This is because an active layer having the above-mentioned predetermined plane orientation was used, so that a quantum well structure with extremely high flatness and little fluctuation in the layer thickness was obtained.
Since the current generated by the piezo effect at the interface between the well and the barrier layer in the active layer is reduced by tilting the c-axis of the film from the active layer surface, the probability of carrier recombination of the electron-hole pair is increased, thereby increasing the luminous efficiency Furthermore, since the crystal growth direction changes in the (1-101) direction in the middle of the crystal from the initial stage, the threading dislocation extending from the vicinity of the substrate interface does not reach the active layer, and non-radiative recombination is reduced. This is probably due to the effect.

Further, in the present invention, generation of cracks could be effectively suppressed. This is AlGaN
The crystal growth of the cladding layer proceeds in the [1-101] direction, and the growth of the nitride semiconductor is started on an inclined plane considerably inclined from the main surface of the substrate, and the growth direction is changed from the middle ((1-1)).
This is considered to be due to the effect of changing in the 01) direction.

Normally, when a laser structure similar to that of the present embodiment is formed on a silicon substrate, several hundred cracks / mm are generated, but almost no cracks are generated by the present invention. This is because cracks are less likely to occur than in the case where the same laser structure as in this embodiment is formed on a sapphire substrate, and the effect of suppressing cracks is remarkable.

As described above, the threshold value of the semiconductor laser device was reduced and the crack was suppressed, so that the device life was improved.

In this embodiment and the following embodiments, the intermediate layer used in the initial stage of the growth includes A
In addition to the lGaInN intermediate layer, an AlInN intermediate layer, AlG
An aN intermediate layer or AlN may be used. In selecting the composition of the intermediate layer, it is preferable to reduce the Ga composition in order to suppress the roughness of the substrate at the beginning of growth, and to reduce the resistance at the interface when a current flows through the silicon substrate. Reduces the Al composition,
It is desirable to dope an n-type impurity such as Si at 10 ¹⁷ cm ⁻³ or more.

In this embodiment, the n-electrode is provided on the silicon substrate, and a current flows from the nitride semiconductor to the substrate. However, a voltage effect is likely to occur at the interface between the nitride semiconductor and the silicon substrate. There is. In order to avoid this problem, it is effective to provide an n-electrode directly on the n-type nitride semiconductor or to provide an electrode for connecting the n-type nitride semiconductor to the silicon substrate, which also serves as a growth suppressing film. You can also.

<Second Embodiment> In the first embodiment, the laser device structure was directly manufactured on a silicon substrate inclined by 7.3 degrees from the (001) plane. It is also possible to form a semiconductor laser device after forming a GaN substrate composed of a continuous film by using the substrate as a base substrate for GaN.

Using a MOCVD (metal organic chemical vapor deposition) method on a silicon substrate which has been subjected to the same processing as in the first embodiment,
By growing the AlInN intermediate layer and then growing GaN, a GaN substrate composed of a continuous film can be manufactured through the growth process shown in FIGS. 7A to 7D.

Specifically, as shown in FIG. 7A, crystal growth starts on the (111) facet. The growing nitride semiconductor is oriented such that the <0001> direction is perpendicular to the slope. On the upper surface of the grown crystal, as shown in FIG.
-101) The plane 70 appears, and during the growth stage, it becomes a crystal having a shape like a triangular prism extending in a stripe shape. Further, as the growth proceeds, the diameter of the triangular prism increases, and as shown in FIG. 7 (c), the adjacent triangular prism crystals finally come into contact with each other. When the growth is further continued, the separated triangular columnar crystals are united to form a flat GaN (1) as shown in FIG.
-101) A GaN crystal film having the plane 72 is obtained.

The intermediate layer used at the beginning of the growth was made of AlI
Similar results were obtained using an nN intermediate layer, an AlGaN intermediate layer, and an AlGaInN intermediate layer.

The wafer is subjected to HVPE (hydride VP).
E) Introduce into the device. While flowing N ₂ carrier gas and NH ₃ respectively at 5 l / min., The temperature of the substrate was set to about 1050 ° C.
Heat up to Then, 100 cc / min of GaCl on the substrate.
To start the growth of a thick GaN film. GaCl is generated by flowing HCl gas through Ga metal maintained at about 850 ° C. In addition, the impurity gas can be arbitrarily doped during the growth by flowing the impurity gas using the impurity doping line which is independently piped to the vicinity of the substrate. In this embodiment, for the purpose of doping Si, the growth is started and, at the same time, monosilane (SiH ₄ )
Was supplied (Si impurity concentration: about 3.8 × 10 ¹⁸ cm ⁻³ ) to grow a Si-doped GaN film.

By the above method, GaN was grown for 8 hours, and GaN having a total thickness of about 350 μm was grown on the silicon substrate. After the growth, the silicon substrate is removed by polishing or etching to obtain an extremely flat GaN substrate having a (1-101) plane. Thus, according to the present embodiment, a GaN substrate having (1-101) plane on the surface can be obtained.

On this n-GaN substrate (film thickness: 100 μm), as in the first embodiment, the n-Al _X1 Ga ₁ -X1N lower cladding layer 103, the n-GaN lower guide layer 104,
Quantum well active layer 105, AlGaN cap layer 10
6, p-GaN upper guide layer 107, p-Al _X2 Ga
_1-X2 N cladding layer _{108, p-Al a In b} Ga 1-ab N
The contact layer 109 is sequentially formed by MOCVD to obtain a semiconductor laser device wafer. Where n-
An n-side metal electrode is formed on the back surface of the GaN substrate. In order to easily obtain a good cleaved end face, the thickness of the wafer is preferably adjusted to 70 to 300 μm, and in this embodiment, it is set to 150 μm.

Each of the semiconductor laser elements (chips) is cut out from a bar by cutting a laser element that is appropriately connected using a dividing method such as a scribing method or a dicing method.
Was manufactured. The obtained semiconductor laser device is placed on a base such as a stem or a lead frame with the metal electrode 110 facing down, and a wire is connected to the n-side metal electrode, or the n-side metal electrode is facing down. The metal electrode 110
Is connected to a wire to supply power from the outside and operate.

When the characteristics of the manufactured semiconductor laser device were measured, a semiconductor laser device having an extremely low oscillation threshold of 20 mA was obtained. This is because the active layer having the predetermined plane orientation has a quantum well structure with extremely high flatness and a small fluctuation in the layer thickness, and the c-axis of the GaN film is inclined from the active layer surface. As a result, the current generated by the piezo effect at the interface between the well and the barrier layer in the active layer is reduced, and the probability of carrier recombination of electron-hole pairs is increased. Since it changes in the (1-101) direction halfway through, it is considered that threading dislocations extending from the vicinity of the interface with the silicon substrate do not reach the active layer and non-radiative recombination is reduced.

Further, also in the present embodiment, the occurrence of cracks could be effectively suppressed. This is Al
This is probably because the crystal growth of the GaN clad layer proceeds in the [1-101] direction, and the silicon substrate was removed during the growth of the AlGaN clad layer.

As described above, in the semiconductor laser device, the threshold value was reduced, and cracks were suppressed, so that the device life was improved.

<Third Embodiment> In the first embodiment, the Si (111) surface is easily formed by an etching method using an etchant (wet etching), and is about 62 cm from the silicon main surface. A slanted surface was obtained. The slope obtained in this manner is a so-called crystal facet, and has not only stable processing accuracy but also excellent flatness, and is extremely excellent as a base for growing a nitride semiconductor.

However, the scope of the present invention is not limited to this. According to various experiments by the inventor, not only the silicon substrate tilted by 7.3 degrees from the (001) plane is used as the main surface, but also in other surfaces, the silicon main surface is partially masked as in the first embodiment. 52,
Further, by changing the temperature and speed of the etching, it was possible to form an inclined groove of 62 degrees with respect to the main surface.

Then, when the surface was examined using the surface, similar results were obtained. That is, similar to the first embodiment, crystal growth can be performed such that the GaN (1-101) plane is substantially parallel to the main surface of the substrate. As a result of such growth, flat GaN (1-101) is obtained. 101) A continuous crystal film having a plane on the surface was obtained. GaN is a crystal with a strong orientation, and is c-axis oriented perpendicular to the main surface in a normal method,
Therefore, only crystals having a C-plane as a main surface were obtained, and it was difficult to obtain crystals having a plane different from the C-plane. However, according to the present invention, a crystal having a GaN (1-101) plane on the surface can be easily obtained.

For example, in this case, on a silicon substrate which is 8.6 degrees off in the [100] direction from the (2-1-1) plane,
By producing a stripe-shaped groove extending in the [01-1] direction, the (211) facet surface can be formed as an inclined surface inclined at 62 degrees from the main surface, and the surface similar to the above is also flat. A GaN crystal film was obtained.

This is because the nitride semiconductor crystal has the (21)
1) Similarly, a flat GaN substrate can be obtained by using a silicon-off substrate having a relationship of an angle of 62 degrees from the (211) plane also with the facet plane grown with the vertical axis as the c-axis. It is thought that it is possible.

As described above, according to the present invention, when a silicon substrate is used, the nitride semiconductor film is liable to grow c-axis oriented crystals on the substrate, and the relationship between the facet and the off angle of the substrate is 62 degrees. By using the substrate, a crystal film having a flat (1-101) facet plane of a nitride semiconductor can be used.

By forming the semiconductor laser device of FIG. 2 on the nitride semiconductor film made of the continuous film thus obtained in the same manner as in the first embodiment, a high-brightness semiconductor on the silicon substrate is formed. Laser elements can now be manufactured. In this semiconductor laser device, the light emitting layer (active layer) has (1-10)
1) It has a surface as a main surface. This is different from an element formed conventionally using a sapphire substrate, a SiC substrate, or a Si (111) substrate, having (0001) as a main surface. A thin film having a wurtzite structure crystal whose main surface is (0001) of a nitride semiconductor is equivalent in band structure in a direction parallel to the main surface, but as in the present invention, the (1-101) plane Is not equivalent in band structure in the direction parallel to the main surface. Therefore, in the light emitting device to which the present invention is applied, the band degeneracy in the direction parallel to the light emitting layer (active layer) is released, and thus the light emitting efficiency is high. Can be realized.

Further, the substrate is not limited to silicon. For example, a semiconductor laser device can be formed even if another cubic substrate such as GaAs is used and the plane orientation is the same as that of the silicon of the first to third embodiments. However, the silicon substrate described in the first to third embodiments is relatively stable in a growth atmosphere when a nitride semiconductor is grown, and it is easy to keep the growth surface flat during crystal growth. Has the advantage of being easily obtained in a stable manner.

In addition, not limited to the cubic crystal, any material may be used as the substrate and the shape of the groove may be processed as specified in this specification. However, in the method of forming a groove in a silicon substrate described in the first to third embodiments, since a so-called facet surface is used as a slope, the flatness and the stability to a growth atmosphere when a nitride semiconductor is grown are excellent. Therefore, there is an advantage that the effect of the present invention is easily and stably obtained.

<Fourth Embodiment> This embodiment is an application of the first embodiment, and the structure around the semiconductor laser device of the first embodiment is as shown in FIG. The groove of the silicon substrate is etched deeper than in the first embodiment, a selective growth portion, that is, a semiconductor laser structure is formed below the surface of the silicon substrate, and an angle of 45 degrees is parallel to the laser end surface. The reflection surface 201 that reflects the laser emission light is formed by etching the silicon substrate.

With this structure, the laser light emitted from the semiconductor laser can be easily extracted vertically from the silicon substrate.

Although the embodiments of the present invention have been described above, it should be understood that the embodiments disclosed herein are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims, and includes all modifications within the scope and meaning equivalent to the claims.

[0076]

According to the present invention, there is provided a nitride semiconductor device formed on a silicon substrate.
Substrate rotated 7.3 degrees along the <1-10> axis from the plane,
Alternatively, by using a plane inclined within 3 degrees in an arbitrary direction from this plane, it becomes possible to obtain a very flat high-quality crystal film having a (1-101) epitaxial plane. By using such a semiconductor laser, it is possible to provide a semiconductor laser device having excellent photoelectric characteristics in which generation of cracks is suppressed at a steep interface.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram for forming a (1-101) facet surface of a nitride semiconductor film.

FIG. 2 is a sectional view showing a semiconductor laser device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a substrate and a nitride semiconductor film used in the present invention.

FIG. 4 shows a first example of a method for manufacturing a semiconductor laser device of the present invention.
It is a figure for explaining a process.

FIG. 5 shows a second example of the method for manufacturing a semiconductor laser device of the present invention.
It is a figure for explaining a process.

FIG. 6 shows a third method of manufacturing the semiconductor laser device of the present invention.
It is a figure for explaining a process.

FIGS. 7A to 7D are views for explaining a fourth step of the method for manufacturing a semiconductor laser device of the present invention.

FIG. 8 is a diagram for explaining a crystal orientation relationship in the silicon substrate of the first embodiment.

FIG. 9 is a perspective view showing a semiconductor laser device structure according to a fourth embodiment.

[Explanation of symbols]

1 Si (001) off substrate, 10 n-AlGaIn
N intermediate layer, 52 mask (silicon oxide film or silicon nitride film), 53 nitride semiconductor crystal, (001) face of 60 silicon, (111) facet face of 61 silicon, (1-101) of 70 nitride semiconductor Facet surface, 71 (0001) facet surface of nitride semiconductor, 72 (1-) of nitride semiconductor in a continuous film state
101) plane, 80 c-axis of nitride semiconductor, 81 growth direction of nitride semiconductor, 102 n-GaN layer, 103
n-Al _X1 Ga _1-X1 N lower cladding layer, 104 n-G
aN lower guide layer, 105 quantum well active layer, 106
AlGaN cap layer, 107 p-GaN upper guide layer, 108 p-Al _X2 Ga _1-X2 N upper cladding layer, 1
_{09 p-Al a In b Ga} 1-ab N contact layer, 11
0,111 metal electrode, 201 reflective surface.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Yoshio Honda Honda 1-1-19 Hiwacho, Chikusa-ku, Nagoya-shi, Aichi 505 Heights Green Pier Room No.2 (72) Inventor Masafumi Yamaguchi 4-54 Suuncho, Mizuho-ku, Nagoya-shi, Aichi Prefecture Nagoya University Suuncho-cho Dormitory No.1 No. 22 Inside Sharp Corporation (72) Inventor Shigenori Ito 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture Inside (72) Inventor Tomoki Ohno 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture (72) Inventor Katsunori Furukawa 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term in Sharp Corporation (reference) 5F073 AA11 AA74 AB19 CA07 CB04 CB0 7 DA05 DA07 DA23 DA25 DA32

Claims (21)

[Claims] 1. A semiconductor laser device comprising: a substrate; and a compound semiconductor layer formed of a nitride semiconductor formed on the substrate.
A groove having a surface inclined at 2 degrees or a surface inclined within 3 degrees in an arbitrary direction from the surface as an inclined surface, wherein the compound semiconductor layer is formed on the inclined surface and the compound semiconductor layer is formed on the inclined surface; A semiconductor laser having a lower cladding layer, an active layer, and an upper cladding layer each formed of a nitride semiconductor on the layer, and the active layer having a plane orientation substantially coincident with the main surface. element. 2. A semiconductor laser device comprising: a substrate; and a compound semiconductor layer formed of a nitride semiconductor formed on the substrate.
A groove having a surface inclined at 2 degrees or a surface inclined within 3 degrees in an arbitrary direction from the surface as an inclined surface, wherein the compound semiconductor layer is formed on the inclined surface and the compound semiconductor layer is formed on the inclined surface; A lower clad layer composed of a nitride semiconductor, an active layer composed of a nitride semiconductor, and an upper clad layer, wherein the lower clad layer and the upper clad layer are each composed of a nitride semiconductor containing Al A semiconductor laser device comprising: 3. A semiconductor laser device comprising: a silicon substrate; and a compound semiconductor layer formed of a nitride semiconductor formed on the silicon substrate, wherein the silicon substrate is located at a distance of 62 from a main surface of the silicon substrate. A groove having a surface inclined at an angle or a surface inclined within 3 degrees in an arbitrary direction from this surface as an inclined surface, wherein the compound semiconductor layer is formed on the inclined surface and each of the nitride semiconductors is A semiconductor laser device having a lower cladding layer, an active layer, and an upper cladding layer composed of: 4. A semiconductor laser device having a silicon substrate and a compound semiconductor layer formed of a nitride semiconductor formed on the silicon substrate, wherein the compound semiconductor layer has a (100) plane of [01]. -1] 7.3 around axis
A silicon substrate having a main surface composed of a plane rotated by degrees or a plane inclined within 3 degrees in an arbitrary direction from this plane, wherein the silicon substrate is (111)
A semiconductor laser having a groove having a surface as a slope, wherein the compound semiconductor layer is formed on the slope, and has a lower cladding layer, an active layer, and an upper cladding layer each composed of a nitride semiconductor. element. 5. The semiconductor laser device according to claim 1, wherein said substrate is made of silicon. 6. The upper cladding layer and the lower cladding layer are made of a nitride semiconductor containing Al.
The semiconductor laser device according to claim 1. 7. The semiconductor laser device according to claim 2, wherein said active layer has a plane orientation substantially coincident with a main surface of said substrate. 8. The semiconductor laser device according to claim 1, wherein a <0001> direction of said compound semiconductor layer is substantially perpendicular to said slope. 9. The semiconductor laser device according to claim 1, wherein said active layer has a (1-101) plane as a plane orientation. 10. The semiconductor laser device according to claim 1, wherein said groove extends along a [11-20] direction of a nitride semiconductor constituting said active layer. 11. The semiconductor laser device according to claim 1, wherein a waveguide stripe structure of laser light is formed along said groove. 12. The semiconductor laser device according to claim 1, wherein a film that suppresses growth of a nitride semiconductor is formed on at least a part of the surface of the substrate other than the slope. 13. A step of forming a groove in the main surface of the substrate, the surface having a surface inclined at 62 degrees from the main surface or a surface inclined within a range of 3 degrees in an arbitrary direction from the surface. Forming a compound semiconductor layer by crystal-growing a nitride semiconductor on the slope, and sequentially laminating a lower cladding layer, an active layer, and an upper cladding layer each composed of a nitride semiconductor on the compound semiconductor layer. A method for manufacturing a semiconductor laser device, comprising: 14. A principal surface comprising a surface rotated by 7.3 degrees around the [01-1] axis or a surface inclined within 3 degrees in an arbitrary direction from this surface. Forming a groove having the (111) plane as a slope in the main surface of the silicon substrate having: a crystal growth of a nitride semiconductor on the slope to form a compound semiconductor layer; Forming a lower cladding layer, an active layer, and an upper cladding layer, each of which is made of a nitride semiconductor. 15. Before forming the compound semiconductor layer,
The method of manufacturing a semiconductor laser device according to claim 13, further comprising a step of forming a film on which growth of a nitride semiconductor is suppressed on at least a part of the surface of the substrate other than the slope. 16. A plurality of grooves are provided on the substrate,
16. The method of manufacturing a semiconductor laser device according to claim 13, wherein the compound semiconductor layers formed on the slopes of the grooves are united according to crystal growth. 17. The method according to claim 16, further comprising a step of removing the substrate after forming the compound semiconductor layer. 18. The method of manufacturing a semiconductor laser device according to claim 13, wherein crystal growth is performed such that a <0001> direction of said compound semiconductor layer is substantially perpendicular to said slope. 19. The method according to claim 19, wherein the upper clad layer and the lower clad layer are formed of a nitride semiconductor containing Al.
A method for manufacturing a semiconductor laser device according to claim 13. 20. The method according to claim 1, wherein the active layer is grown so as to have a plane orientation substantially coincident with a main surface of the substrate.
20. The method for manufacturing a semiconductor laser device according to any one of 3 to 19. 21. The method according to claim 20, wherein the active layer has a (1-101) plane as a plane orientation.