JP2001168451A - Manufacturing method for surface-emitting semiconductor element, and semiconductor laser device using the element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize spatial oscillation mode, related to a semiconductor laser device of surface light-emitting type optical excitation. SOLUTION: In a surface-emitting semiconductor element which constitutes a semiconductor laser device of surface-emitting optical excitation, a GaN buffer layer 12, an Alz4Ga1-z4N carrier confinement layer 13, and a GaN light confinement layer 14 are sequentially laminated at 1,050 deg.C on a GaN substrate 11, an then an Inx3Ga1-x3N/Inx2Ga1-x2N multiplex quantum well active layer 15 and a GaN layer 16 are laminated sequentially with a growing temperature lowered to 800 deg.C or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a surface emitting semiconductor device and a semiconductor laser device using the surface emitting semiconductor device, and more particularly to a method for manufacturing a surface emitting semiconductor device using InGaN as an active layer. And a semiconductor laser device using the surface emitting semiconductor element.

[0002]

2. Description of the Related Art Recently, a stripe type semiconductor laser using an InGaN quantum well having an oscillation wavelength in a violet wavelength region near 400 nm as an active layer has been put into practical use. For example, Jap.J.Appl.phys.Lett., Vol.37.ppL issued in 1998
In 1020, Nakamura et al.
A laser diode formed by stacking GaN / GaN / AlGaN is introduced.

[0003] Further, in "The Blue Laser Diode" issued by Springer in 1997, it is possible to further increase the wavelength to the blue / green region by increasing the amount of In in InGaN with the above-mentioned material-based laser. It is stated that it is possible. However, InGaN does not
Since there is a problem that the spatial nonuniformity of the In composition increases when the composition is increased, LEDs have been put to practical use in a wavelength region of 460 nm or more, but laser oscillation has not been obtained. Particularly, laser oscillation in a green region having a large In composition is extremely difficult.

[0004] Laser light sources in the blue and green regions are important for applications such as laser displays, excitation light sources for various fluorescent analyses, and light sources for writing color images on silver halide photographic materials. I have.

On the other hand, as a semiconductor laser device having a semiconductor thickness of about 400 nm, conventionally, an n-GaN low-temperature buffer layer and a GaN buffer layer are grown on a sapphire C-plane substrate by normal pressure CVD, and then striped. Si
An O2 mask is formed. Next, an n-GaN buffer layer, an n-In _0.05 Ga _0.95 N buffer layer, an n-Al
After growing the _0.1 Ga _0.9 N cladding layer and the n-GaN optical guide layer at 1050 ° C., lowering the temperature of the crystal growth furnace to 800 ° C., growing the InGaN active layer, and then raising the temperature of the crystal growth furnace again to 1050 ° C. ° C to p-GaN
Optical guide layer, p-Al _0.1 Ga _0.9 N clad layer, p-G
An aN cap layer was being grown. In this crystal growth step, the InGaN active layer cannot be grown at a high temperature of 1000 ° C. or higher, so it is necessary to grow the temperature at about 850 ° C. However, for the growth of subsequently grown layers, especially AlGaN cladding layers, 10
A high temperature of 00 ° C. or higher is suitable, and it is necessary to raise the growth temperature again.

However, at such a high temperature, there is a problem that the unevenness of the In composition of the already grown InGaN active layer increases due to the movement of In in the crystal. Therefore, in order to form a more uniform InGaN active layer and realize a long-wavelength blue-green semiconductor laser, it is necessary to grow high-quality GaN or AlGaN at a low temperature. It is difficult to achieve this.

Further, when the composition of In of InGaN is increased, the strain increases due to an increase in the lattice constant, which tends to cause non-uniformity. Alternatively, there is a problem in that the energy dispersion is large and the non-uniform spread of the semiconductor laser medium is large, so that the peak gain is low and oscillation cannot be obtained.

Therefore, US Pat. No. 5,461,637 and US Pat. No. 5,561,637 disclose a semiconductor laser device different from the conventional current injection type.
No. 6,278,63 proposes an optically pumped surface emitting semiconductor laser device. However, since this semiconductor laser device uses the thermal lens effect of semiconductor (the effect of increasing the refractive index as the temperature rises), it is necessary to raise the temperature in the oscillating portion of the basic active medium, There is a disadvantage that the sensitive and spatial oscillation mode becomes unstable. Therefore, a surface emitting type optically pumped semiconductor laser device which overcomes such a drawback has been proposed by the present applicant in Japanese Patent Application No. 11-257529.

[0009]

As described above, in a semiconductor laser device having an oscillation wavelength in the blue / green region, especially in the case of a current injection type, the oscillation mode is increased due to the unevenness of the In composition of InGaN during the manufacturing process. Was unstable. In addition, even the currently reported light-excited surface-emitting type semiconductor laser device has a problem that the spatial oscillation mode is unstable.

In view of the above circumstances, it is an object of the present invention to provide a highly efficient semiconductor laser device having an oscillation wavelength in a blue / green region.

[0011]

According to the present invention, there is provided a semiconductor laser device comprising: an excitation light source comprising a semiconductor laser element; and an excitation light source which emits laser light having a wavelength longer than that of the excitation light emitted from the excitation light source. A surface-emitting type semiconductor device having an active layer on a substrate and a mirror formed on the substrate side of the active layer or on the side opposite to the substrate; and a mirror disposed outside the surface-emitting type semiconductor device. In a semiconductor laser device having at least one external mirror forming a resonator, an active layer of the surface emitting semiconductor element is made of InGaN, and an upper layer of the active layer made of InGaN has a composition other than AlGaN. It is characterized by being made of a group V compound.

Here, the upper layer of the active layer means a layer laminated above the active layer.

Further, III-V having a composition other than AlGaN
The group III compound may be GaN or InGaN.

A method for manufacturing a semiconductor laser device according to the present invention
In the method for manufacturing a surface-emitting type semiconductor element constituting the above-described semiconductor laser device, an active layer made of InGaN is formed, and all layers formed thereafter are formed at 1000 ° C. or lower.

[0015]

In a conventional current injection type short-wavelength semiconductor laser device, an active layer made of InGaN has been formed so far, and a layer to be grown thereafter, particularly a layer made of AlGaN, has been required to have a thickness of 1000. A high temperature of at least ℃ is suitable, and it is necessary to raise the growth temperature again. However, at such a high temperature, the non-uniformity of the In composition of the already grown InGaN active layer is caused by the In composition in the crystal.
And the spatial oscillation mode becomes unstable. However, according to the semiconductor laser device of the present invention, there is provided a semiconductor laser device including a semiconductor laser element and a surface-emitting type semiconductor element which is excited by a laser beam emitted from the semiconductor laser element and oscillates with an external resonator. The active layer of the surface-emitting type semiconductor device is composed of InGaN, and the upper layer of the active layer composed of InGaN is composed of a III-V compound having a composition other than AlGaN. Since the composition does not become non-uniform, 450 nm to 55 nm
A stable laser oscillation of blue and green of 0 nm can be obtained.

Further, by using a GaN or InGaN group III-V compound having a composition other than AlGaN,
Higher quality crystals can be obtained at a deposition temperature of 1000 ° C. or lower. If the In composition of InGaN is smaller than the In composition ratio of InGaN in the active layer, the light confinement effect can be enhanced.

Further, according to the method of manufacturing a surface emitting semiconductor device of the present invention, the growth temperature of a layer formed after the formation of the InGaN active layer of the surface emitting semiconductor device constituting the semiconductor laser device is 1000 ° C. Because it does not exceed
Non-uniform composition of the InGaN active layer does not occur, and high reliability can be obtained.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

A semiconductor laser device according to a first embodiment of the present invention will be described. FIG. 1 is a cross-sectional view of a surface-emitting type semiconductor device constituting the semiconductor laser device. First,
The surface-emitting type semiconductor device will be described.

[0020] Jap. J. Appl. Phys. Lett., Vol.
37. An n-GaN substrate is formed by the method described in ppL1020. As shown in FIG. 1, 1050 is deposited on a GaN (0001) substrate 11 by atmospheric metalorganic vapor phase epitaxy.
GaN buffer layer _{12, Al z4 Ga 1-z4} N carrier confinement layer (0 <Z4) 13, successively after growing a GaN light confining layer 14 at ° C., with the growth temperature lowered to 800 ° C. or less, an In _x3
Ga1 _-x3N / _{Inx2Ga1 -x2N} multiple quantum well active layer (however, _{Inx3Ga1 -x3N} is a quantum well layer and _Inx2G
a _1-x2 N is a barrier layer, which has a relation of 0 <x2 <x3 <1)
15. Laminate the GaN layer 16 and terminate the crystal growth. Thereafter, a SiO ₂ / ZrO ₂ multilayer optical filter 17 (a multilayer of SiO ₂ and ZrO ₂ alternately laminated by an electron beam evaporation method or the like. However, the first layer on the GaN layer 16 is SiO 2 ₂ ), a coating film 18 is formed on the back surface of the GaN substrate 11, and is cut into chips to complete the surface-emitting type semiconductor element 19.

Here, the multilayer optical filter 17 is configured to have a high reflectance of 90% or more at the oscillation wavelength and a low reflectance of 5% or less at the wavelength of the excitation light. The coating film 18 is configured to be an antireflection film for the oscillation wavelength.

Next, a description will be given of a semiconductor laser device using the above-described surface-emitting type semiconductor element 19, and FIG. 2 shows a configuration diagram of the semiconductor laser device.

As shown in FIG. 2, the semiconductor laser device of the present invention has an excitation light source of 370 having InGaN as an active layer.
A broad-stripe semiconductor laser device 21 having a width of about 100 .mu.m oscillating at .about.410 nm is used.
, An external resonator 27 including the concave surface of the concave mirror 25 and the multilayer optical filter 17 of the surface-emitting type semiconductor element 19, and a wavelength selection element 24 in the external resonator 27. The multilayer optical filter 17 functions as a mirror. Wavelength 450
It is possible to configure a resonator type surface emitting semiconductor laser device that oscillates at ５０550 nm.

According to the semiconductor laser device of the present invention, InGaN
Due to the good uniformity of the active layer, the InGaN-based blue-green region (450-5
(26 nm) light 26 can be oscillated. In addition, crystal growth is performed at a low temperature, and unlike a normal current injection laser diode, doping is not required. Therefore, heat treatment at a relatively high temperature for activating Mg is not required. Unevenness of the InGaN active layer can be avoided. Further, the doping material M
There is no problem of diffusion of g and the like, and there is no deterioration with time due to short-circuit, and the life can be extended.

As shown in FIG. 2B, the light emitted from the semiconductor laser element for excitation may be incident on the surface-emitting type semiconductor element 19 at an angle.

Next, a semiconductor laser device according to a second embodiment of the present invention will be described, a surface-emitting type semiconductor device constituting the semiconductor laser device will be described, and a sectional view thereof is shown in FIG. First, the surface emitting semiconductor device will be described.

GaN is grown by atmospheric metalorganic vapor phase epitaxy.
On a (0001) substrate 31, a GaN buffer layer 32, an AlN / GaN multilayer optical filter 33 (Al
N and GaN are alternately stacked in a multilayer structure, and the first layer on the GaN buffer layer is AlN. After growing the GaN optical confinement layer 34 in this order, the growth temperature is lowered to 800 ° C. or less, and the In _x3 Ga _{1 -x3N} / In _x2 Ga _{1 -x2} N multiple quantum well active layer (where In _x3 Ga _{1 -x3} N is the quantum well layer, in _x2 Ga _1-x2 N is a barrier layer, 0 <x2 <x
3 <1) 35 and the GaN layer 36 are stacked, and the crystal growth is terminated. Then, Z is deposited by electron beam evaporation or the like.
An rO ₂ film 37 is formed, and a ZrO ₂ film 38 is formed on the back surface of the GaN substrate 31.
Is formed and cleaved into chips to complete the surface-emitting type semiconductor element 39.

Here, the multilayer optical filter 33 is configured to have a high reflectance of 90% or more at the oscillation wavelength and a low reflectance of 5% or less at the wavelength of the excitation light. The ZrO ₂ film 37 is an antireflection film for the oscillation wavelength,
The rO ₂ film 38 is configured to be an anti-reflection film for the excitation light wavelength.

Next, a description will be given of a semiconductor laser device using the above-mentioned surface-emitting type semiconductor element 39, and FIG. 4 shows a configuration diagram of the semiconductor laser device.

As shown in FIG. 4A, this semiconductor laser device has an excitation light source of 370 having InGaN as an active layer.
A perforated heat sink 23 on which the GaN substrate 31 side of the surface-emitting type semiconductor element 39 is mounted, a concave mirror 25 serving as an output mirror, and a concave surface using a broad stripe semiconductor laser element 21 oscillating at about 410 nm and having a width of about 100 μm. The external resonator 27 includes the concave surface of the mirror 25 and the multilayer optical filter 33 of the surface-emitting type semiconductor element 39. The external resonator 27 includes the wavelength selection element 24. The multilayer optical filter 33 plays the role of a mirror. This allows
A resonator type surface emitting semiconductor laser device that oscillates light 26 having a wavelength of 450 to 550 nm can be configured.

The semiconductor laser device according to the present embodiment is
Since the GaN substrate 31 is transparent to the excitation light, and the sapphire substrate and the like that are often used are also transparent,
It is characterized in that excitation light can be incident from the substrate side. Furthermore, since these substrates have a large heat conduction coefficient, there is an advantage that if a heat sink as shown in FIG. 4 is formed, heat can be easily dissipated and beam deformation due to a thermal lens or the like is very small.

As shown in FIG. 4B, light emitted from the semiconductor laser element for excitation may be incident on the surface-emitting type semiconductor element 39 at an angle.

Next, a surface-emitting type semiconductor device according to a third embodiment of the present invention will be described, and a cross-sectional view thereof is shown in FIG.

As shown in FIG. 5, a GaN (0001) substrate 41 is formed at 1050.degree.
After growing a GaN buffer layer 42, a multilayer Bragg reflection film 43 of 20 cycles of AlN / GaN, and a GaN light confinement layer 44 in this order, the growth temperature is lowered to 800 ° C. or less, and
_{x3Ga1 -x3N} / _{Inx2Ga1 -x2N} multiple quantum well active layer 45
(However, In _x3 Ga _1-x3 N is a quantum well layer and In
_{x2Ga1 -x2N} is a barrier layer, which has a relationship of 0 <x2 <x3 <1), and a GaN layer 46 is stacked, thereby terminating the crystal growth. After that, a ZrO ₂ film 47 is formed by an electron beam evaporation method or the like, and chipped by cleavage to complete a surface-emitting type semiconductor element 49. Here, the multilayer Bragg reflection film 43 is made of GaN and Al having a thickness corresponding to / wavelength of the oscillation wavelength in the crystal.
N for 20 cycles, and the GaN buffer layer 42
The first layer above is AlN. The ZrO ₂ film 47 is configured to be an antireflection film for the oscillation wavelength.

Next, a semiconductor laser device using the surface-emitting type semiconductor element 49 formed as described above will be described.
FIG. 6 shows the configuration diagram.

As shown in FIG. 6, a cavity surface emitting semiconductor laser device that oscillates light 26 having a wavelength of 450 to 550 nm from the concave mirror 25 by attaching the GaN substrate 41 to the heat sink 23 and arranging it. Can be configured. As an excitation light source, a broad stripe semiconductor laser device 21 having an active layer of InGaN and oscillating at 370 to 410 nm and having a width of about 100 μm is used.
Excited from the end face opposite to the 41 side. Since the entire surface of the substrate of the surface-emitting type semiconductor element 49 can be brought into contact with the heat sink, the heat radiation effect is good and the influence of the thermal lens can be reduced. Further, for example, by inserting a Brewster plate inside the resonator 27 as the polarizing element 28, the polarization can be controlled.

Further, in order to obtain a single longitudinal mode, a wavelength conversion element, a Lyot filter, an etalon, or a plurality of these may be inserted inside the resonator.

Further, by directly modulating the semiconductor laser element 21 used as an excitation light source of the semiconductor laser device, it is possible to obtain a modulated signal modulated at high speed. This is a characteristic that cannot be realized by the conventional solid-state laser.

As described in the above embodiment, a broad area type semiconductor laser device can be used as an excitation light source, so that high output, for example, 1 W to 10 W or more can be achieved. Therefore, the obtained oscillation output is several hundred mW or more.
High output of several W or more is possible.

Further, since the surface emitting semiconductor device of this embodiment is photoexcited, it differs from a normal current injection semiconductor laser device in that heat generation due to an increase in electric resistance in a semiconductor Bragg reflection film or the like and a decrease in efficiency occur. There is no problem, such as a conventional surface emitting laser, a complicated composition such as providing a composition gradient layer at the interface between the layers constituting the Bragg mirror, or reducing the resistance by local doping. No structure is required, and the creation process is simpler.

Next, a surface-emitting type semiconductor device constituting a semiconductor laser device according to a fourth embodiment will be described, and a sectional view thereof is shown in FIG.

As shown in FIG. 7, a 1050 ° C. GaN (0001) substrate 51 is
After growing a GaN buffer layer 52, an Al _z4 Ga _1-z4 N carrier confinement layer 53 (0 <z4), and a GaN light confinement layer 54 in this order, the growth temperature is lowered to 800 ° C. or less,
_{nx3Ga1 -x3N} / _{Inx2Ga1 -x2N} multiple quantum well active layer
55 (however, In _x3 Ga _1-x3 N is a quantum well layer,
_{nx2Ga1 -x2N} is a barrier layer, which has a relation of 0 <x2 <x3 <1), and a GaN layer 56 is stacked to terminate the crystal growth.
Thereafter, the active layer 55 and the GaN layer 56 are etched by dry etching so as to form a cylinder having a diameter of 0.6 mm. Next, SiO ₂ and Zr having a thickness corresponding to １ ／ wavelength of the oscillation wavelength were formed by electron beam evaporation.
A reflection film 57 made of O ₂ is formed, a ZrO ₂ antireflection film 58 is formed on the back surface of the GaN substrate 51, and cut into chips by cleavage to complete a surface-emitting type semiconductor element 59. Here, the reflection film 57 is formed by laminating 12 periods of SiO ₂ and ZrO ₂ having a thickness corresponding to 波長 wavelength in the crystal, and the first layer on the GaN light confinement layer is SiO ₂ . . ZrO ₂ anti-reflective coating
Numeral 58 is configured to be an antireflection film with respect to the oscillation wavelength.

Here, in the semiconductor laser device shown in FIG. 6, instead of the surface emitting semiconductor element 49, a surface emitting semiconductor element 59 is attached to the heat sink on the side of the reflection film 57 made of SiO ₂ and ZrO _2. Construct a laser device. In such a semiconductor laser device, since the active region of the surface-emitting type semiconductor element is partially formed, oscillation light whose spatial mode is well controlled can be obtained.

Next, a surface-emitting type semiconductor device constituting a semiconductor laser device according to a fifth embodiment of the present invention will be described, and a sectional view thereof is shown in FIG.

As shown in FIG. 8, a GaN (0001) substrate 61 is formed on a GaN (0001) substrate 61 at a temperature of 1050.degree.
After growing a GaN buffer layer 62, an Al _z4 Ga _1-z4 N carrier confinement layer 63 (0 <z4), and a GaN light confinement layer 64 in this order, the growth temperature was lowered to 800 ° C. or less,
_{nx3Ga1 -x3N} / _{Inx2Ga1 -x2N} multiple quantum well active layer
65 (however, In _x3 Ga _1-x3 N is a quantum well layer,
_{nx2Ga1 -x2N} is a barrier layer, which has a relationship of 0 <x2 <x3 <1, and the first crystal growth is completed.

Thereafter, the active layer 65 is etched by dry etching so as to form a column having a diameter of 1.0 mm. The reason why such processing is performed is to suppress the higher-order transverse mode oscillation and to realize a stable fundamental transverse mode oscillation by partially forming the active layer as in the fourth embodiment. .

Thereafter, in the second crystal growth, 8
At 00 ° C., a GaN layer 66 is laminated. Next, e-beam evaporation
The thickness of S corresponding to Ｓ wavelength of the oscillation wavelength
iO _TwoAnd ZrO_TwoForming a 12-period reflective film 67
(Here, the first layer on the GaN layer 66 is SiO 2_Twofilm
Is). Next, the ZrO 2_TwoAnti-reflective
A stop film 68 is formed and formed into chips by cleavage.
The conductor element 69 is completed.

Here, in the semiconductor laser device shown in FIG. 6, a surface-emitting type semiconductor element 69 is mounted instead of the surface-emitting type semiconductor element 49, and the reflection film 67 side is attached to a heat sink to constitute a semiconductor laser device. In this semiconductor laser device, the spatial mode is satisfactorily controlled by an active region formed partially in the surface emitting semiconductor element.

In all of the above embodiments, the active layer of the surface-emitting type semiconductor device is formed at a temperature of 800 ° C. or less, but is preferably formed at a temperature of 600 ° C. or more and 850 ° C. or less.

In the fourth and fifth embodiments, in order to obtain desired characteristics without impairing the function and effect of the active region formed partially in the surface-emitting type semiconductor device, it is necessary to use laser light. It is preferable that the size of the active region partially formed on the plane parallel to the plane from which the laser beam exits is 0.1 to 10 times the diameter of the laser beam in the active region. This is because the smaller the active region, the better the spatial mode controllability. However, if the active region is too small, the shielding amount of the fundamental mode light increases, the loss increases, and there is a possibility that high output is limited. Because there is.

In the semiconductor laser devices according to all of the above embodiments, a broad area type semiconductor laser element is used as an excitation light source. However, the present invention is not limited to this. MOPA (Master Oscillator Power Amplifir)
e), and α-DFB (angled grating-distribute)
d feedback) A laser may be used.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a surface-emitting type semiconductor device constituting a semiconductor laser device according to a first embodiment of the present invention;

FIG. 2 is a diagram showing a semiconductor laser device according to a first embodiment of the present invention;

FIG. 3 is a cross-sectional view illustrating a surface-emitting type semiconductor device constituting a semiconductor laser device according to a second embodiment of the present invention;

FIG. 4 is a view showing a semiconductor laser device according to a second embodiment of the present invention;

FIG. 5 is a cross-sectional view illustrating a surface-emitting type semiconductor device constituting a semiconductor laser device according to a third embodiment of the present invention;

FIG. 6 shows a semiconductor laser device according to a third embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a surface-emitting type semiconductor device constituting a semiconductor laser device according to a fourth embodiment of the present invention;

FIG. 8 is a sectional view showing a surface-emitting type semiconductor device constituting a semiconductor laser device according to a fifth embodiment of the present invention;

[Explanation of symbols]

11,31,41,51,61 GaN substrate 12,32,42,52,62 GaN buffer layer 13,53,63 Al _z4 Ga _1-z4 N carrier confinement layer 14,34,44,54,64 GaN light confinement Layer 15,35,45,55,65 In _x3 Ga _1-x3 N / In _x2 Ga _1-x2
N multiple quantum well active layer 16,36,46,56,66 GaN layer 17 SiO ₂ / ZrO ₂ multilayer optical filter 18 coating 19,39,49,59,69 surface-emitting type semiconductor device 21 semiconductor laser element 23 heat sink 27 Resonator 33 AlN / GaN multilayer optical filter 37,38,47,58,68 ZrO ₂ film 43 20-period AlN / GaN multilayer Bragg reflection film 57 12-period SiO ₂ / ZrO ₂ reflection film 67 12-period SiO ₂ / ZrO ₂ reflective film

Claims (3)

[Claims] 1. An excitation light source comprising a semiconductor laser element, and an active layer on a substrate, which is excited by the excitation light source and emits laser light having a wavelength longer than the wavelength of the excitation light emitted from the excitation light source. A surface-emitting type semiconductor device having a mirror formed on the substrate side or on the side opposite to the substrate; and at least one external mirror disposed outside the surface-emitting type semiconductor device and forming the mirror and an external resonator. The semiconductor laser device according to claim 1, wherein an active layer of the surface emitting semiconductor element is made of InGaN, and an upper layer of the active layer made of InGaN is made of a group III-V compound having a composition other than AlGaN. apparatus. 2. The semiconductor laser device according to claim 1, wherein the group III-V compound having a composition other than AlGaN is made of GaN or InGaN. 3. The method for manufacturing a surface-emitting type semiconductor device constituting a semiconductor laser device according to claim 1, wherein an active layer made of InGaN is formed, and all layers formed thereafter are formed at 1000 ° C. or lower. A method for manufacturing a surface-emitting type semiconductor device, comprising: