JP2828002B2 - Semiconductor light emitting device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short-wavelength semiconductor light-emitting device used in the fields of optical communication and optical information processing, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, demands for short-wavelength semiconductor light-emitting devices have been increasing in many fields, and intensive studies have been made on ZnSe-based and GaN-based materials. With a ZnSe-based material, continuous oscillation at room temperature of a short-wavelength semiconductor laser with an oscillation wavelength of about 500 nm has been achieved, and research and development for practical use have been continued. On the other hand, even with GaN-based materials, blue light-emitting diodes with high luminance have recently been realized. The reliability as a light emitting diode is not inferior to other semiconductor light emitting element materials, and it seems that application to a semiconductor laser is sufficiently possible.

[0003]

SUMMARY OF THE INVENTION However, GaN
Since the physical properties of the system material are not well understood and the crystal structure is a hexagonal system, it is not known whether the element structure similar to that of the conventional cubic system material can provide sufficiently practical characteristics.

The present invention has been made in view of the above-mentioned problems, and has as its object to provide a high-performance semiconductor light-emitting device using a unique characteristic of an electronic band structure of a hexagonal compound semiconductor. .

[0005]

In order to achieve the above object, a semiconductor laser of the present invention uses a distortion characteristic of an electronic band structure inherent to a hexagonal compound semiconductor to provide a simple high performance semiconductor laser. It will be realized. Specifically, a semiconductor light emitting device having a low threshold current is realized by applying non-isotropic (anisotropic) strain to the c-plane of a hexagonal compound semiconductor.

We have found that when a non-isotropic (anisotropic) strain is applied to the c-plane of a hexagonal compound semiconductor, the effective mass of holes near the upper end of the valence band is reduced. By utilizing this property, non-isotropic (anisotropic) strain is applied to the c-plane of the active layer composed of a hexagonal compound semiconductor grown in the c-axis direction, so that the threshold current is increased. , A semiconductor light emitting device having a low density can be realized. Here, isotropic means a strain applied hydrostatically (isotropically) in the c-plane.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The distortion characteristics of the valence band structure of the hexagonal compound semiconductor used in the present invention will be described below with reference to the drawings.

FIG. 1 shows an AlG when no strain is applied.
Regarding the aN / GaN quantum well structure, the electron band structure of the valence band of the GaN quantum well layer is shown. This quantum well structure includes an AlGaN barrier layer and a GaN quantum well layer. The thickness of the quantum well layer is about 4 nm. In FIG. 1, a curve a represents the energy band of the heavy hole in the first level, and a curve b represents the energy band of the heavy hole in the second level. Curve c represents the energy band of the first level of light holes, and curve d represents the energy band of the second level of light holes.

FIG. 1 shows that the effective mass of a hole near the upper end of the valence band (near the wave number 0) is Zincblend
This shows that it is considerably larger than the e-type compound semiconductor. When uniaxial strain in the c-axis direction or isotropic (biaxial) strain in the c-plane is applied to the GaN quantum well layer,
The effective mass of the hole near the top of the valence band is almost the same as in the case of no distortion. The uniaxial strain in the c-axis direction refers to a case where there is a strain only in the c-axis direction of the hexagonal compound semiconductor, and the biaxial strain in the c-plane is a strain having a magnitude equal to the axes perpendicular to each other. In some cases, this is also an isotropic distortion.

By the way, when a non-isotropic (anisotropic) strain is applied to the c-plane of the hexagonal compound semiconductor, the deformation potential is D5, and the strain in two orthogonal directions in the c-plane is e.
_xx , e _yy , and the shear strain in the c-plane is _yy ,
Not isotropic in the plane (anisotropic) deformation energy due to distortion is applied can be described in the form of _{D5 (e xx -e yy + 2ie} xy).

FIG. 2 shows that the deformation energy is 10 m in the c-plane.
4 shows an electron band structure of a valence band of a GaN quantum well layer in an AlGaN / GaN quantum well structure when non-isotropic (anisotropic) strain of eV is applied. As is apparent from FIG. 2, by applying a non-isotropic distortion,
The “valence band curvature” in a region with a small wave number is small. For this reason, it can be seen that the effective mass of the hole near the upper end of the valence band is considerably smaller than that in the case of no distortion. This means that the state density near the upper end of the valence band is reduced, which corresponds to the fact that the injection current density required for laser oscillation is small. Therefore, it can be seen that in the semiconductor laser using the active layer in which the non-isotropic strain is applied to the quantum well layer, the oscillation threshold current becomes small.

FIG. 3 shows the strain dependence of the threshold current density when non-isotropic (anisotropic) strain is applied to the c-plane. The horizontal axis represents the deformation energy, and the vertical axis represents the threshold current density normalized by the value in the case of no distortion. The figure collectively shows the results when the threshold gain is changed. As is clear from FIG. 3, the threshold gain value is not isotropic (anisotropic) in any case.
The application of the strain significantly reduces the threshold current density.

Although FIG. 3 does not consider step distortion in the c-plane, the same effect can be obtained when step distortion is applied in the c-plane.

As described above with reference to FIGS. 1 to 3, in a semiconductor light emitting device using a hexagonal compound semiconductor for an active layer, an element having a small threshold current can be obtained by using non-isotropic strain for the active layer. It can be seen that it can be realized.

Hereinafter, a device in which a non-isotropic strain is introduced into a hexagonal compound semiconductor and a method of manufacturing the same will be specifically described.

Embodiment 1 The structure of a semiconductor light emitting device according to an embodiment of the present invention will be described. As a hexagonal compound semiconductor, I
An AlGaInN-based material that is a II-V group compound semiconductor is used. The distortion is introduced in a direction parallel to the c-plane.
In the case where a wurtzite type is used for the AlGaInN light emitting element layer 100, a band structure (valence band) is obtained when a uniaxial strain is applied in a direction perpendicular to the (0001) axis (parallel to the c-plane).
Can be changed. As described above, the characteristics of the light emitting element are improved as a result.

As shown in FIG. 4, when a stripe-shaped groove 102 is formed in a sapphire substrate 101, the direction of the thermal expansion coefficient appears on the substrate, and then the substrate is grown on the other surface where the stripe groove 102 is not formed. It is possible to apply uniaxial strain to the AlGaInN light emitting layer 100 in the x direction in the figure. By using the light emitting layer 100 as an active layer, a semiconductor light emitting device having a small threshold current can be realized.

FIG. 5 shows a specific manufacturing method. First, a stripe-shaped mask 104 is formed on one main surface of a sapphire substrate 103. After that, using a mask 104 and an etching solution such as hot sulfuric acid, a striped groove 105 is formed.
To form Further, when a material such as AlN is selectively grown using the mask 104, the A
An 1N buried layer 106 is formed. As a result, a distribution of the thermal expansion coefficient occurs in the thickness direction, and when the crystal growth of the AlGaInN light emitting layer 107 is subsequently performed at a high temperature of 1000 ° C. or more, uniaxial distortion can be generated in the substrate. Metalorganic vapor phase epitaxy is used for crystal growth, but AlGaIn
It is said that about 1100 ° C. is good for N. Then, when the temperature is returned to room temperature, the AlGaInN light emitting layer 107 can be in a state where uniaxial strain is applied.

Here, by forming the AlN buried layer 106, thermal expansion is increased, heat transfer from the heating mechanism is improved, and a larger strain can be applied. Further, the absolute amount of distortion to be applied can be controlled by the width and depth of the groove 105, so that a structure optimal for the light emitting element can be obtained.

As a method of applying uniaxial distortion to the crystal, formation of a stripe-shaped oxide film can be considered. FIG.
FIG. 7 is a structural view of a semiconductor light emitting device according to one embodiment of the present invention.

Before crystal growth, a stripe-shaped oxide film 109 is formed on one main surface of the sapphire substrate 108.

Thereafter, when the temperature is raised to 1000 ° C. or more for crystal growth, the sapphire substrate 108 and the oxide film 109 can be curved in the direction of Z in FIG. By growing the crystal in this state and returning the temperature to room temperature, a crystal having a strain in the Z direction can be obtained. In this case, the amount of distortion is controlled by the width and pitch of the stripe. For example, when fabricating a semiconductor laser, it is appropriate that the width is about 5 microns and the pitch is about 10 microns.

As a similar method, AlGaIn
There is a method of growing an N light emitting layer by metal organic chemical vapor deposition. After that, a stripe-shaped oxide film 109 is formed. At that time, by forming the oxide film at a high temperature of about 500 ° C., the same curvature can be generated and uniaxial strain can be applied to the crystal. The same effect can be obtained by forming a stripe-shaped oxide film 109 and then performing a heat treatment at a high temperature.

A similar effect can be realized by utilizing the bimetal effect of a metal. FIG. 8 is a structural view of a semiconductor light emitting device according to one embodiment of the present invention. A
In the case of manufacturing an lGaInN light emitting device, a SiC substrate 112
It is effective to use. AlGaInN in advance
The light emitting layer 116 is grown by metal organic chemical vapor deposition. After that, the stripe-shaped first Au layer 1 is formed on the Ni layer 113.
By forming 14, the SiC substrate 112 can be curved in the Z direction in the figure by the bimetal effect. As a result, uniaxial strain can be applied to the AlGaInN light emitting layer 116. In this case, the Ni layer 113 is
Since the semiconductor light-emitting element has electrical ohmic characteristics with respect to No. 12, the effect when the semiconductor light-emitting element is manufactured is large.

FIG. 9 is a structural view of a semiconductor light emitting device according to one embodiment of the present invention. This is a method in which a stress is applied from the outside when crystal growth is performed. The sapphire substrate 117 is fixed on a tray 119 having a surface with a curvature R prepared in advance and fixed using a jig 118. Thereafter, a light emitting layer is grown on the substrate 117 and taken out.
Reference numeral 17 indicates that the light emitting layer is strained to return to the original state. A feature of this method is that the amount of distortion to be applied can be controlled by mechanically changing the curvature of the tray 119.

(Embodiment 2) FIG. 10 shows a second embodiment.
Wurtzite In_xGa_1-xN / Al_yGa_1-yN quantum well half
FIG. 3 is a sectional view of an element of a conductor laser. In the well layer_xGa_1-x
N, Al in barrier layer _yGa_1-yN is used.

According to the metal organic chemical vapor deposition method (1100)
An AlN buffer layer 202 on a LiTaO ₃ substrate 201,
_{n-Al z Ga 1-z} N cladding layer _{203, Al y Ga 1-y} N
The first light guide layer _{204, In x Ga 1-x} N / GaN multi-quantum well active layer 205 (InxGa1-xN quantum well layer, a stacked structure of GaN quantum well _{layer), Al y Ga 1-y} N second light guide layer _{206, p-Al z Ga 1} -z N cladding layer 2
07 are formed continuously.

After that, a ridge stripe 208 is formed by etching, and a SiO2 insulating film 209 is deposited.
An opening 210 is formed in the SiO ₂ insulating film 209 for current injection.
And 211 are formed. And finally the anode electrode 2
12 and the cathode electrode 213 are formed.

This wurtzite type InGaN / AlGaN amount
The layer structure of a subwell semiconductor laser depends on its composition and material.
The growth temperature is often different, but for example,
When the growth method is used, 8 excluding the AlN buffer layer 202
It is produced in the range of 00 to 1100 ° C. Therefore growing
The crystal returned to room temperature after completion has a difference in thermal expansion coefficient from the substrate.
Causes distortion. It should be noted that it is polycrystalline during growth.
Subsequent AlN buffer layer 202 as a seed crystal
As crystals grow, (1100) LiTaO _ThreeSubstrate 2
The difference in lattice constant between the layer 01 and the other layers is reflected in the strain.
And almost none. Of course n-Al_zGa_1-zN crush
P-Al_zGa_1-zN clad layer 207
The lattice constant differs between materials in heterostructures
It is possible that this lattice constant difference is reflected in the distortion.
Material and film to prevent misfit dislocations, etc.
You can choose the thickness. However, the distortion due to the aforementioned difference in thermal expansion coefficient
Cannot be avoided. Therefore, in the present invention, this distortion is positively used.
I use it.

FIG. 15 shows the in-plane thermal expansion coefficients of the LiTaO ₃ substrate 201 used as the substrate and the wurtzite-type GaN crystal. In this embodiment, (1100) LiTaO
Since three substrates are used, the coefficient of thermal expansion has anisotropy in the plane, and is represented by a (0001) direction and a (11｀20) direction perpendicular to the (0001) direction as shown in FIG. The wurtzite-type GaN-based material is (000) regardless of the plane orientation of the substrate.
1) Since the crystal grows in the orientation, each layer is formed perpendicular to the (0001) direction. The coefficient of thermal expansion of the wurtzite GaN-based material is isotropic in the (0001) plane, and is 5.6 × 10 ⁻⁶ for GaN. Materials of any composition of AlGaInN mixed crystals have a coefficient of thermal expansion near this. On the other hand, L
The iTaO3 substrate is 1.2 × 10 ⁻⁶ in the (0001) direction.
And GaN have a smaller coefficient of thermal expansion than
Conversely, in the (1｀20) direction, it has a thermal expansion coefficient of 2.2 × 10 ⁻⁵ , which is much larger than that of GaN. Thus, in the semiconductor laser of FIG. 10 (1100) LiTaO ₃ substrate 2
01 were prepared by crystal growth _{n-Al z Ga 1-z} N
A cladding layer _{203 p-Al z Ga 1-} z N cladding layer 2
If sufficiently thicker than the crystal up to 07, for example, the growth temperature is assumed to 1000 ° C. and higher than room _{temperature, n-Al z Ga 1-} z N cladding layer 203 from p-Al _z Ga when cooled to room temperature Crystals up to the _1-z N cladding layer 207 include:
Assuming that the distortion in the (0001) direction is e _xx and the distortion in the (11｀20) direction is e _yy , e _xx = −0.44% and e _yy = 1.6%.
Becomes In this manner, anisotropic strain (non-isotropic strain) can be formed in the surface of the In _x Ga ₁ -xN / GaN multiple quantum well active layer 205, so that the state density of the valence band can be greatly increased. And the threshold current of the laser can be reduced.

However, the n-Al _z Ga _{1 -z} N clad layer 2
If the total thickness of the crystal growth layer from 03 to _{p-Al z Ga 1-z} N cladding layer 207 is thick, the distortion due to thermal expansion coefficient difference between the substrate as described above, i.e. withstand e _xx and e _yy It is also conceivable that dislocation defects are caused and strain is relaxed. In this case, as shown in FIG.
A LiTaO ₃ substrate may be used which is tilted θ in the (0001) direction and φ in the (11｀20) direction. Due to this inclination, the strain entering each direction of the crystal growth layer becomes e ′ _xx = −0.4 cos θ e ′ _yy = 1.6 cos φ and can be reduced. Therefore, introduction of dislocation defects can be prevented by appropriately selecting q and f.
If q and f are selected so that e ′ _xx + e ′ _yy = 0, the effect of preventing dislocation defects is particularly high.

In this embodiment, LiTaO is used as the substrate.
₃ , but other non-linear optical crystals such as LiNbO ₃
And KTiOPO4, KNbO _3, LiB ₆ material O ₁₃ and the like similarly increases the anisotropy of thermal expansion coefficient as LiTaO3, is possibly stabilized at the growth temperature used.

(Embodiment 3) FIG. 13 is a sectional view of an element of a wurtzite-type InGaN / AlGaN quantum well semiconductor laser showing a third embodiment. By crystal growth, an AlN buffer layer 302 and an n-
AlzGa1-zN cladding layer 303, AlyGa1-y
N first light guide layer 304, InxGa1-xN / Ga
Continuous N multiple quantum well active layer _{305, Al y Ga 1-y} N second optical guide layer 306, p-AlzGa1-zN first cladding layer _{307, p-Al z 'Ga} 1-z' N strain induced layer 308 It is formed. Then once the substrate is taken out of the crystal growth _{apparatus, p-Al z 'Ga 1} -z' N distortion introduced layer 3 by etching
08 was processed into a stripe shape having a width of 2mm _{to, p-Al z Ga 1-} z N second cladding layer 309 after returning to the growth apparatus again
Grow. After depositing the SiO2 insulating film 310, the opening 3 is formed in the SiO2 insulating film 310 for current injection.
11 and 312 are formed. Finally, an anode electrode 313 and a cathode electrode 314 are formed.

Here, the p-Al _{z '} Ga ₁ -z'N strain introducing layer 30
P-Al _z G _{a1- z} N first cladding layer 307 a Al composition ratio z '8 and _{p-Al z Ga 1-z} N second cladding layer 309
Is selected to be larger than the Al composition ratio z of p-Al
_{Since the z ′} Ga ₁ -z′N strain introducing layer 308 is smaller, FIG.
As shown in (1), compressive strain can be introduced into surrounding crystals.

As described above, the local distortion can be introduced by p
In the width of the _{-Al z 'Ga 1-z'} N strain induced layer 308 is as small as about 2 mm, when the width is sufficiently large p-Al _z 'G
Only strain is introduced into the a _{1 -z'N} strain introduction layer 308 itself, so that strain cannot be introduced into nearby crystals. p-Al z is _{'Ga 1-z'} N strain induced layer 308 can introduce distortion around the crystal with a plane perpendicular to the stripe because it is fabricated into a stripe shape, distortion in a plane parallel to the stripes Is not introduced. As a result, even in the In _x Ga ₁ -xN / GaN multiple quantum well active layer 305, the strain can be introduced only in the plane perpendicular to the stripe, so that anisotropy occurs in the strain and the state density of holes is reduced. it can. Since the strain to the In _x Ga ₁ -xN / GaN multiple quantum well active layer 305 can be increased as the distance from the p-Al _{z '} Ga ₁ -z'N strain introduction layer 308 becomes shorter, the p-Al
The thickness of the _z Ga _1-z N first cladding layer 307 can be adjusted by properly setting.

[0036] In this embodiment _{p-Al z 'Ga 1-} z' N
Although selected larger than the Al composition ratio of the strain introduction layer 308 z 'a _{p-Al z Ga 1-z} N first cladding layer 307 and the _{p-Al z Ga 1-z} N Al composition ratio of the second cladding layer 309 z Conversely, the same anisotropic strain can be produced even when the size is selected to be small. In particular, when z ′ is smaller than z, p-Al _{z ′} G
The a _{1-z ′} N strain introduction layer 308 can also realize an optical waveguide structure. The p-Al _{z '} Ga _{1 -z'N} strain introducing layer 308
This is because having a refractive index greater than -Al _z Ga _1-z N second cladding layer 309. Therefore, a refractive index waveguide structure can be realized very easily.

(Embodiment 4) FIG. 16 shows a method of manufacturing a semiconductor laser according to an embodiment of the present invention.

[0038] using the crystal growth method of a metal-organic vapor phase epitaxy method or the like, for example, (0001) plane Al _x Ga _y In _z N system fabricated on a sapphire substrate (0 ≦ x ≦ 1,0 ≦ y ≦ 1 ,
FIG. 16 shows a chip of the semiconductor laser 401 satisfying 0 ≦ z ≦ 1).
As shown in (a), first, it is arranged on the submount 402 at a high temperature of 200 ° C. As shown in FIG. 17, the structure of the submount 402 is composed of LiTaO ₃ 403 and a solder material 404. LiTaO ₃ 403 is a dielectric of anisotropic crystal, and the semiconductor laser 401 is mounted on a plane perpendicular to the (0001) plane, for example, on the (1120) plane or the (1100) plane.

As the solder material 404, for example, Pb-Sn or the like is used. The solder material melted at 200 ° C. solidifies when cooled to room temperature, and the semiconductor laser 401
2 fixed on. The thermal expansion coefficient of LiTaO ₃ 403 in the a-axis direction is 22 × 10 ⁻⁶ / K, and that in the c-axis direction is 1.
It is 2 × 10 ⁻⁶ / K. That is, the rates of thermal expansion in the x-axis direction and the y-axis direction in FIG. 16A are significantly different, and when the semiconductor laser 401 is fixed to the submount 402, uneven stress is applied to the semiconductor laser 401. . The amount of uniaxial stress applied to the semiconductor laser 401 can be controlled by increasing the temperature. In other words, a higher stress can be applied as the temperature is higher.

The semiconductor laser 401 of this embodiment uses a wurtzite crystal. By applying a uniaxial stress in a direction perpendicular to the (0001) axis, this crystal can change the band structure of the valence body, can reduce the effective mass, can reduce the state density, As a result, the threshold current and drive current of the semiconductor laser can be reduced, and a highly reliable laser can be obtained.

As described above, by combining a wurtzite type semiconductor light emitting device with an anisotropic crystal whose coefficient of thermal expansion greatly differs depending on the orientation, it is possible to greatly improve the characteristics of the semiconductor light emitting device.

In this embodiment, the semiconductor laser 401 is (0
001) plane, for example, (1120) plane or (1
Although the description has been made assuming that the submount is mounted on the 100) plane, the plane orientation does not matter as long as it is a submount to which uniaxial stress is applied.

(Embodiment 5) FIG. 18 shows a method of manufacturing a semiconductor laser according to another embodiment of the present invention.

[0044] using the crystal growth method of a metal-organic vapor phase epitaxy method or the like, for example, (0001) plane Al _x Ga _y In _z N system fabricated on a sapphire substrate (0 ≦ x ≦ 1,0 ≦ y ≦ 1 ,
FIG. 18 shows a chip of the semiconductor laser 501 satisfying 0 ≦ z ≦ 1).
As shown in (a), first, it is arranged on the submount 502 at a high temperature of 180 ° C. The structure of the submount 502 is as shown in FIG.
It is composed of an i-Mn alloy 504 and Pb-Sn solder 505. The Fe—Ni alloy 503 is a material called an invar, whose length hardly changes even when the temperature changes. Further, the Fe—Ni—Mn alloy 504 is a material whose thermal expansion is remarkable as the temperature rises. By bonding the Fe—Ni alloy 503 and the Fe—Ni—Mn alloy 504 together, a submount that is curved by a change in temperature can be obtained.

The solder material melted at 180 ° C. solidifies when the temperature drops to room temperature, and the semiconductor laser 501 is mounted on the submount 5.
02. When the semiconductor laser 501 is fixed to the submount 502, a non-uniform stress having a large stress in one direction is applied to the semiconductor laser 501.
The amount of uniaxial stress applied to the semiconductor laser 501 can be controlled by increasing the temperature.

The semiconductor laser 501 of this embodiment uses a wurtzite crystal. By applying a uniaxial stress in a direction perpendicular to the (0001) axis, this crystal can change the band structure of the valence body, can reduce the effective mass, can reduce the state density, As a result, the threshold current and drive current of the semiconductor laser can be reduced, and a highly reliable laser can be obtained.

As described above, by combining the wurtzite-type semiconductor light-emitting device and the bimetal, the characteristics of the semiconductor light-emitting device can be greatly improved.

Although the present embodiment has been described using a submount as shown in FIG. 19, the effect of the present invention is great if the submount is curved in one direction. For example, a structure as shown in FIG. 20 may be used. That is, Fe-Ni
-On the back surface of the Mn alloy 504, a Fe-Ni alloy 503 that does not expand due to a temperature change is formed in a stripe shape. Even with this structure, the submount can be curved in the direction perpendicular to the stripe as shown in FIG.

FIG. 21 shows a method of manufacturing a semiconductor laser according to another embodiment of the present invention. Using the crystal growth method of the metal organic chemical vapor deposition or the like, Al _x produced, for example, (1120) plane sapphire substrate Ga _y In _z N system (0 ≦ x ≦ 1, 0
As shown in FIG. 21, first, a chip of the semiconductor laser 551 satisfying ≦ y ≦ 1, 0 ≦ z ≦ 1) is disposed on the submount 552. Thereafter, ultraviolet rays are applied to the ultraviolet curing resin 554 while applying stress to the semiconductor laser 553 from above using the collet 553 for weighting, thereby fixing the semiconductor laser 551 to the submount 552. When the semiconductor laser 551 is fixed to the submount 552, the semiconductor laser 5
51 is vertically stressed.

The semiconductor laser 551 of this embodiment uses a wurtzite crystal. By applying a uniaxial stress in a direction perpendicular to the (0001) axis, this crystal can change the band structure of the valence body, reduce the effective mass, reduce the state density, and as a result, The threshold current and drive current of the semiconductor laser can be reduced, and a highly reliable laser can be obtained.

In this embodiment, the semiconductor laser is applied with stress from the upper surface as shown in FIG. 21. However, a structure in which the semiconductor laser is applied from the side surface may be employed, for example, a structure as shown in FIG. That is, the semiconductor laser 551 is installed in the concave portion provided in the submount 555. A hexagonal compound semiconductor is used for the active layer of the semiconductor laser, and the crystal grows in the c-axis direction.

On both sides of the submount 555, a load screw 557 for applying a stress to the side surface of the semiconductor laser 551 via a load leaf spring 556 is provided.
The laser 551 is fixed to the concave portion with an ultraviolet effect resin 554, and the laser 551 is rotated by rotating a weight screw 557.
Uniaxial strain can be introduced into the c-plane of the active layer. With this uniaxial strain, a semiconductor laser with a small threshold current can be realized.

Although the present embodiment has been described using the semiconductor laser grown on the (1120) substrate, the effect of the present invention can be obtained if the structure is such that uniaxial stress is applied in the direction perpendicular to the (0001) plane. large.

Although the present embodiment has been described using an ultraviolet curable resin, any material can be used as long as the semiconductor laser and the submount can be fixed. For example, a thermosetting resin may be used.

(Embodiment 6) FIG. 23 shows a process of manufacturing an AlGaInN-based semiconductor light emitting device according to an embodiment of the present invention.

The crystal was grown by the reduced pressure MOVPE method, and the element structure was formed by two MOVPE growths. First, as shown in FIG. 23A, the 6H—SiC substrate 601 was degreased and cleaned, and then the first crystal growth was performed by the MOVPE method. The growth method will be described in detail. Hydrogen gas was introduced into the reaction chamber of the MOVPE apparatus, and the pressure in the reaction chamber was reduced to 1 /
After setting the pressure to 10 atm, the substrate 601 is placed in hydrogen gas for 11 atm.
The temperature was raised to 00 ° C., and the surface of the 6H—SiC substrate 601 was cleaned.

Then, after lowering the substrate temperature to 600 ° C., ammonia gas was introduced as a group V raw material onto the surface of the 6H—SiC substrate 601, and after 10 seconds, trimethylaluminum was supplied as a group III raw material to form a 50 nm-thick film. A non-single crystal AlN layer 602 was deposited. Thereafter, the supply of trimethylaluminum was stopped once, the substrate temperature was raised to 900 ° C., and trimethylaluminum was again supplied as a group III raw material, and a single-crystal AlN layer 603 having a thickness of 5 μm was deposited.

Next, SiO ₂ was used as an etching mask.
23, a width of 3 μm and an interval of 2 as shown in FIG.
Two μm stripe grooves were formed.

After removing the etching mask, the MOV
A second crystal growth was performed by the PE method. Hydrogen gas was introduced into the reaction chamber of the MOVPE apparatus, and the pressure in the reaction chamber was reduced to 1/1.
After the pressure was set to 0 atm, the 6H-SiC substrate 601 was heated to 1100 ° C. in a mixed atmosphere of hydrogen gas and ammonia gas to clean the surface. Then, the substrate temperature is set to 10
After the temperature was lowered to 30 ° C., trimethyl aluminum, trimethyl indium and trimethyl gallium were supplied as group III raw materials, and as shown in FIG. 23C, a Si-doped n-type AlGaInN cladding layer 604 having a thickness of 3 μm and a 20 nm An AlGaInN active layer 605 and a 2 μm-thick Mg-doped p-type AlGaInN cladding layer 606 were continuously laminated on the entire surface including the inside of the stripe groove. Finally, a p-side electrode 607 and an n-side electrode 608 were formed to complete the laser structure.

From the above manufacturing steps, when laminating the above double hetero structure, the composition of the two stripe grooves 609 and the incorporation of each group III element into the crystal at the flat portion 610 between the two stripe grooves. Since the efficiencies differ, a composition change occurs. In this case, the composition change corresponds to the change in the lattice constant. In the flat portion 610 sandwiched by crystals having different lattice constants from both sides, a stress is generated in the lateral direction from the groove 609 on both sides.
Therefore, in the flat portion, distortion can be selectively applied only in the direction perpendicular to the stripe direction. this is,
Almost uniaxial strain occurs in the in-plane direction of the active layer, and the state density of the valence band can be reduced. Further, since the active layer is curved in the flat portion 610 between the two stripe grooves, a semiconductor laser with low threshold current and stable transverse mode can be realized using the flat portion 610 as a light emitting portion.

The amount of strain applied to the flat portion 610 serving as a light emitting portion can be easily controlled by changing the interval and depth of two stripe grooves and the thickness of the Si-doped n-type AlGaInN cladding layer 604.

(Embodiment 7) FIG. 24 shows a manufacturing process of an AlGaInN-based semiconductor light emitting device according to a manufacturing method of an embodiment of the present invention. The difference from the sixth embodiment is that a concave portion is provided instead of the stripe groove portion. By utilizing the inclined portion of the concave portion, strain can be applied to the active layer at the flat portion of the concave portion.

The crystal was grown by the reduced pressure MOVPE method, and the element structure was formed by MOVPE growth twice. First, FIG.
As shown in FIG. 4A, after the 6H—SiC substrate 651 was degreased and cleaned, first crystal growth was performed by MOVPE. The growth method will be described in detail. Hydrogen gas was introduced into the reaction chamber of the MOVPE apparatus, and the pressure in the reaction chamber was reduced to 1/1.
After setting to 0 atm, the substrate 651 is
The temperature was raised to 0 ° C., and the surface of the 6H—SiC substrate 651 was cleaned. Next, after lowering the substrate temperature to 600 ° C., ammonia gas was introduced as a group V material onto the surface of the 6H—SiC substrate 651, and after 10 seconds, trimethylaluminum was supplied as a group III material to provide a non-single-crystal having a thickness of 50 nm. An AlN layer 652 was deposited. Thereafter, the supply of trimethylaluminum was temporarily stopped, the substrate temperature was raised to 900 ° C., and trimethylaluminum was again supplied as a group III raw material to deposit a single-crystal AlN layer 653 having a thickness of 5 μm.

Next, SiO ₂ was used as an etching mask.
As shown in FIG. 24B, a stripe groove having a width of 3 μm was formed.

After removing the etching mask, the MOV
A second crystal growth was performed by the PE method. Hydrogen gas was introduced into the reaction chamber of the MOVPE apparatus, and the pressure in the reaction chamber was reduced to 1/1.
After the pressure was set to 0 atm, the temperature of the 6H-SiC substrate 651 was increased to 1100 ° C. in a mixed atmosphere of hydrogen gas and ammonia gas to clean the surface. Then, the substrate temperature is set to 10
After cooling to 30 ° C., trimethylaluminum, trimethylindium and trimethylgallium were supplied as group III raw materials, and as shown in FIG. 24C, a 3 μm-thick Si-doped n-type AlGaInN cladding layer 654 and a 20 nm-thick An AlGaInN active layer 655 and a 2 μm-thick Mg-doped p-type AlGaInN cladding layer 656 were continuously laminated on the entire surface including the inside of the stripe groove. Finally, a p-side electrode 657 and an n-side electrode 658 were formed to complete the laser structure.

From the above manufacturing steps, when laminating the above-mentioned double hetero structure, the composition of the stripe groove side surface portion 659 and the efficiency of taking in each group III element into the crystal in the stripe groove flat portion 660 are different. A composition change occurs. In this case, the change in the composition corresponds to the change in the lattice constant, and a stress is generated in the lateral direction in the flat portion 660 sandwiched by crystals having different lattice constants from both sides. Therefore, in the flat portion 660, distortion can be selectively applied only in the direction perpendicular to the stripe direction as indicated by the arrow. Therefore, uniaxial strain can be applied in the in-plane direction of the active layer of the flat portion 660,
A semiconductor laser with low threshold current and stable transverse mode can be realized using the flat portion 660 as a light emitting portion. Note that the amount of strain applied to the flat portion 660 serving as the light emitting portion is determined by the stripe groove width, the depth, and S.
It can be easily controlled by changing the thickness of the i-doped n-type AlGaInN cladding layer 654.

(Embodiment 8) As shown in FIG. 25A, GaN crystal layers 802 and 80 are formed on a (0001) sapphire substrate 801 by metal organic chemical vapor deposition (MOVPE).
3 is deposited. The raw material is trimethylgallium (TM
G), ammonia (NH3), and hydrogen gas as a carrier gas for the raw material. The growth pressure is 100 Torr. A part of the substrate is selectively irradiated with a light beam such as an excimer laser from a viewing window provided in the reaction chamber during the vapor phase growth. The growth temperature is usually 500 ° C., which is lower than the temperature at which a single crystal is obtained. This means that G with different lattice constants
This is because the aN crystal layers are two-dimensionally arranged.

FIG. 26 shows data showing that the lattice constant of the GaN crystal changes depending on the laser irradiation intensity during vapor phase growth. This is because if the growth temperature is sufficiently low, polycrystalline G
This is probably because an aN crystal was formed and the apparent lattice constant was increased. From this, it is considered that when a high intensity laser beam is irradiated, the growth temperature of the irradiated portion is selectively increased and single crystal is formed. As shown in FIG. 25A, when an excimer laser is selectively irradiated onto the (0001) sapphire substrate 801 at an intensity of 10 kW to perform metal organic chemical vapor deposition, the lattice constant in the region irradiated with the laser light originally has A GaN crystal layer 802 having a single crystal value is deposited, and a polycrystalline GaN crystal layer 803 having a large lattice constant is deposited in a region not irradiated with laser light. As a result, as shown in FIG. 25B, in the boundary region between the GaN crystal layer 802 and the GaN crystal layer 803, distortion occurs in the direction along the boundary line, and there is no distortion in the direction perpendicular to the boundary line. An anisotropic strain state can be produced. If this is used for, for example, an active layer of a gallium nitride based semiconductor laser, a remarkable improvement in characteristics is expected. The growth temperature is 700 at which a polycrystal is obtained.
The same effect can be obtained if the temperature is lower than 500C, so that the present invention is not limited to 500C.

Embodiment 9 Further, as shown in FIG. 27, a GaN crystal layer is deposited on the GaN crystal layer 802 and the GaN crystal layer 803 by metal organic chemical vapor deposition at 1000 ° C. without irradiating a laser beam. . When such a growth is performed, the lattice constant of the GaN crystal layer 805 on the polycrystalline GaN crystal layer 803 is large, and the GaN crystal layer 805 on the single crystal GaN crystal layer 802 is large.
The lattice constant of the crystal layer 804 can be reduced. It is important that the growth temperature in this case is higher than the temperature at which the GaN crystal layer 802 and the GaN crystal layer 803 are deposited, and a polycrystalline GaN crystal layer 803 having a large lattice constant is used as a buffer layer to form a crystal closer to a single crystal. A GaN single crystal layer 805 having good properties can be deposited. Therefore, a higher quality GaN single crystal layer can be manufactured than the manufacturing method in which only a laser beam is applied as shown in FIG.

(Embodiment 10) At this time, by changing the film thicknesses of the GaN crystal layer 802 and the GaN crystal layer 803 shown in FIG. 25, the information of the lattice mismatch from the sapphire substrate can be controlled. Crystal layer 802 and Ga
The thickness of the GaN crystal layer 805 is changed by changing the thickness of the N crystal layer 803.
Can be changed, and the amount of strain can be controlled. If a two-dimensionally strained GaN single crystal layer manufactured by such a manufacturing method is used as, for example, an active layer of a gallium nitride based semiconductor laser, a remarkable improvement in characteristics is expected.

In the present embodiment, a method of growing a GaN single crystal has been described. However, it is apparent that the same effect can be obtained with AlN, InN, and a mixed crystal thereof. The same effect can be obtained not only with a sapphire substrate but also with a substrate such as SiC or ZnO.

Embodiment 11 An eleventh embodiment of the present invention will be described. FIG. 28 is a cross-sectional view showing a manufacturing process in the example. The sapphire substrate 1101 is set in a reaction tube of a metal organic chemical vapor deposition apparatus, and the sapphire substrate 1101 is set.
Was heated to 1000 ° C., and hydrogen, ammonia, trimethylaluminum, and trimethylgallium were supplied to the reaction tube to reduce the AlGaN cladding layer 1102 to 5 μm.
By supplying m, hydrogen, ammonia, trimethylaluminum, trimethylindium, and trimethylgallium, the n-type AlGaInN cladding layer 1103 is reduced to 5 μm.
m, hydrogen, ammonia, trimethylindium, and trimethylgallium to supply the InGaN active layer 1
P-type AlG by supplying 0.01 μm of hydrogen, ammonia, trimethylaluminum, trimethylindium, trimethylgallium, and diethyl zinc.
The aInN cladding layer 1105 is grown to a thickness of 2 μm by an organic metal growth method to form a double hetero structure.

At this time, the AlInGaN cladding layer 1
103, 1105 and the InGaN active layer 1104
Has a lattice constant larger than that of the AlGaN cladding layer 1102, and thus has a compressive strain.

Subsequently, an insulating film 1106 is deposited on the side surfaces of the sapphire substrate 1101, the AlGaN cladding layer 1102, the AlInGaN cladding layers 1103 and 1105, and the InGaN active layer 1104 by thermal CVD, and the structure shown in FIG. To form

Subsequently, the AlG was formed by photolithography and reactive ion etching with carbon tetrafluoride.
The insulating film is etched so that the side surface of the aN cladding layer 1102 is exposed to form a structure as shown in FIG.

Subsequently, the AlGaN cladding layer 1 was etched from the side by reactive ion beam etching with chlorine.
102 is etched by 5 μm to form a structure as shown in FIG. AlGaInN 1103, InGaN 110
4. AlGaInN 1105 is an AlGaN cladding layer 1
The portion where AlGaN cladding layer 1102 is not etched is free from stress because the lattice constant is large by including In as compared with that containing In. It is illustrated as if it was extended. The portion where AlGaN 1102 is located below is smaller than the original lattice constant, and compressive strain is introduced.

FIG. 29 shows a sectional structural view after the insulating film is removed and a plan view seen from above. 1107 and 1108 are
FIG. 4 is a schematic diagram showing a lattice constant of a crystal constituting the InGaN active layer 1104 when viewed from above. In the region 1107, the InGaN active layer 1104 has an AlGaN cladding layer 110 having a smaller lattice constant than this active layer.
InGaN active layer 1104
Is subjected to stress from all directions perpendicular to the growth direction, resulting in a two-dimensional compressive strain. However, because of the compressive strain, it extends in the growth direction.

On the other hand, since the AlGaN cladding layer 1102 does not exist below the region 1108, no stress is applied to the right direction in FIG. Become. Therefore, compressive strain can be applied in a selective direction.

As described above, in the active layer 1104, A
At the boundary between the lower portion of the lGaN layer 1102 and the portion that has not been removed (the boundary between 1107 and 1108),
Strain occurs in the direction indicated by the arrow, and this strain becomes uniaxial strain in the in-plane direction, and the state density of the valence band can be reduced. In the portion 1107, the active layer 110
4 receives isotropic compressive strain in the in-plane direction, and this strain does not contribute to the reduction of the threshold current. However, 1
Non-isotropic distortion occurs at the boundary between 107 and 1108, which greatly contributes to the reduction of the threshold current.

As shown in FIG. 28D, instead of the AlGaN cladding layer 1102, an InGaN cladding layer is used.
By using an AlGaInN active layer instead of the InGaN active layer 1104, the AlGaInN
It is also possible to selectively apply tensile strain to the boundary between the portion where the lower portion of the active layer has the InGaN cladding layer and the portion where the lower portion does not have the InGaN cladding layer.

Instead of using the above-described dry etching such as patterning of an insulating film and reactive ion beam etching, it is also possible to use selective etching by electrolysis. At this time, since the etching of the layer to be etched is promoted by the electrolysis more than in the case of many layers, it is possible to accelerate the etching by adding a high concentration of impurities and contacting the electrodes in the electrolyte and applying a voltage. Becomes In order to prevent electrical interference between the layer to be etched and the layer forming the device structure,
It is necessary to stack an insulating layer of about μm or more.

(Embodiment 12) Next, a twelfth embodiment of the present invention will be described. FIG. 30 is a schematic diagram of the manufacturing process in the example. The sapphire substrate 1201 is set in a reaction tube of a metal organic chemical vapor deposition apparatus,
1 is heated to 1000 ° C., and hydrogen, ammonia, and trimethylgallium are supplied to the reaction tube to form a GaN crystal growth nucleus 1202 on the substrate. At this time, in order to reduce the formation density of growth nuclei, the pressure in the reaction tube is set to 1
Keep the pressure as low as 0 Torr.

Subsequently, GaN 1203 is grown by supplying ammonia and trimethylgallium at a further reduced pressure of 5 Torr. At this time, since the pressure is very small, no new crystal growth nucleus is formed on the substrate, and the crystal is not vertically stacked on the substrate, so that the condition that the single crystal is most likely to be deposited on the crystal side wall is obtained. Therefore, the GaN crystal 1203 grows spirally around the crystal nucleus 1202 in parallel with the substrate, forming a spiral thin film.

FIG. 31 is a schematic diagram showing the state of the unit cell 1204 of the GaN crystal 1203 at this time. No stress is applied in the radial direction, but in the circumferential direction, tensile stress is applied toward the outer periphery. Therefore, as long as dislocations do not occur, the GaN crystal 1203 is an asymmetric strained crystal (strain that is not isotropic) having tensile strain only in the circumferential direction.

Subsequently, the pressure in the reaction tube was increased to 80 Torr, and the conditions were set so that lamination in a direction perpendicular to the substrate was possible.
By supplying hydrogen, ammonia, trimethylaluminum, and trimethylgallium on the GaN spiral thin film 1203, the n-type AlGaN cladding layer 1205 is 5 μm thick.
By supplying hydrogen, ammonia, trimethylindium, and trimethylgallium, the InGaN active layer 120 is formed.
6 was supplied with 0.01 μm of hydrogen, ammonia, trimethylaluminum, trimethylgallium, and diethyl zinc to form a p-type AlGaN cladding layer 1207 of 2 μm.
It grows up to μm to form a double heterostructure.

According to this method, an asymmetric strained crystal can be easily formed only by changing the pressure during growth without using steps such as etching and selective regrowth. Therefore, the semiconductor laser manufactured by this method has a small threshold current.

(Embodiment 13) FIG. 34 is a schematic sectional view of a growth apparatus used in an embodiment of the present invention. 101 in the figure
Reference numeral 1 denotes a reaction tube made of quartz, into which a raw material gas is introduced from a gas inlet 1012. Reaction tube 1011
A susceptor 1013 made of carbon is arranged in the inside, and a sample substrate 1014 is installed on the upper surface of the susceptor. The susceptor is provided with a rotation mechanism in order to obtain in-plane uniformity of the composition and film thickness of the epitaxial layer. The susceptor is induction-heated by the high-frequency coil 1015 arranged around the reaction tube. A thermocouple 1016 disposed in the susceptor enables monitoring and control of the substrate heating temperature. The gas exhaust port 1017 is connected to a vacuum pump 1018 so that the pressure inside the reaction tube can be adjusted and gas can be exhausted.

Next, a crystal growth method using the above-described apparatus will be described with reference to FIGS. First, an α-Al ₂ O ₃ (sapphire) substrate 1031 having a plane orientation (0001) whose surface has been cleaned by an organic solvent, a hydrochloric acid-based chemical treatment and pure water cleaning is placed on the susceptor 1013,
It is fixed by the substrate holder 1021. Gas inlet 1
From 012, high-purity hydrogen gas passed through a purification device is introduced to replace the atmosphere in the reaction tube 1011. After introducing hydrogen gas for several minutes, the vacuum pump 1018 is operated to maintain the pressure in the tube at 10 Torr. When the pressure is stabilized, the susceptor is induction-heated by the high-frequency coil 1015, and after the temperature of the sample substrate 1014 reaches 1200.degree.
Hold for a minute to clean the substrate surface.

Next, the temperature of the substrate was lowered to 400 ° C., and then TMG (trimethylgallium) and N
H ₃ (ammonia) is introduced from the gas inlet 1012 to deposit an amorphous GaN film 1035 until the film pressure becomes 0.1 μm. At this time, in mind substrate temperature is low decomposition efficiency of NH ₃ for lower than normal growth conditions, the flow rate ratio of NH3 and TMG is 10000: 1. At this time, if the growth temperature was higher than the above temperature, three-dimensional growth, that is, hexagonal columnar island-like growth occurred, and a uniform amorphous GaN film could not be obtained.

After the GaN film 1035 is deposited, after the substrate temperature has dropped, the sample substrate is once removed from the reaction tube 1011 and subjected to a photolithography process in a direction perpendicular to the R plane of the sapphire substrate as shown in FIG. The amorphous GaN deposition film 1035 was left in a stripe shape. Here, the R surface is a surface that is a cross section of the sapphire substrate 31 in FIG.
That is, it extends in a direction perpendicular to the R plane. The width and spacing of the stripes are 5 μm and 50 μm, respectively.

After sufficient washing with pure water, the sample substrate was returned into the reaction tube 1011 again, and this time, instead of hydrogen gas, NH _{3 was used.}
The sample substrate 1014 is heated until the temperature of the sample substrate 1014 reaches 1100 ° C. in the above-described manner while flowing the gas to clean the surface of the sample substrate.

Next, TMG and NH ₃ are introduced from the gas inlet 1012, and a GaN film is epitaxially grown by a usual two-stage growth method. That is, the substrate temperature is set to 600
In order to promote the three-dimensional growth of the GaN film 1033, that is, the hexagonal columnar island growth until the film thickness of 0.05 μm, the substrate temperature is increased to 1050 ° C. The GaN film 1034 was epitaxially grown until the thickness became 5.0 μm. At this time, NH3
And the flow ratio of TMG was 300: 1. The GaN film 1034 grown epitaxially becomes an amorphous-like crystal where the amorphous GaN film 1035 exists below. This is because only the amorphous is deposited on the amorphous. Here, the film is referred to as an amorphous GaN film 1036.

The amorphous GaN film 10
The region sandwiched between 36 is an element formation region 1041. This is because, as described later, this region has a low dislocation density and the strain in the crystal is not isotropic (has anisotropy).
It has become. That is, the strain due to the difference in lattice constant between the substrate 1031 and the GaN film 1034 remains in the direction parallel to the stripe, and the strain is relaxed in the direction perpendicular to the stripe.

As described above, Ga having a non-isotropic strain
If, for example, a semiconductor laser is formed in the element forming region 1041 of the N film, a small threshold current can be produced from the strained state.

Next, the present inventors describe the crystal quality of the GaN epitaxial layer obtained by the method of the above embodiment. FIG. 36 shows, for comparison, the conventional two-step growth method.
The distribution of dislocations obtained from a transmission electron microscope image of a cross section of a 5 μm thick GaN epitaxial layer 1033 or 1034 grown on an α-Al ₂ O ₃ (sapphire) substrate 1031 having a (0001) plane orientation is shown.

The dislocations 1032 uniformly generated from the interface 1037 with the substrate 1031 due to the strain due to the lattice mismatch extend to the surface of the epitaxial layer while meandering in the epitaxial growth direction. In the figure, the dislocations that are visible or disappear in the middle are out of the field of view of the transmission electron microscope because the dislocations extend in the direction perpendicular to the cross section, and the dislocations disappear. is not. When the dislocation density is estimated from a transmission electron microscope image, dislocations of 10 ⁹ / cm ² or more occur uniformly, and the lattice strain applied to the epitaxial layer is isotropic in the plane.

On the other hand, a GaN epitaxial layer according to this embodiment will be described with reference to FIG. FIG. 37 also schematically shows the distribution of dislocations obtained from the transmission electron microscope image of the cross section. It was found that up to a thickness of 3 μm, considerable dislocations reached a portion where crystal defects were concentrated on the amorphous GaN film 1035 formed in stripes. That is, while the strain is relaxed in the direction 1039 perpendicular to the stripe, the strain is likely to be inherent in the crystal in the parallel direction 1040. Therefore, an epitaxial layer in which the strain due to lattice mismatch is biased in the direction 1040 parallel to the stripe is obtained.

As another effect, the dislocation density of the element forming region 1041 sandwiched between the stripes is 10 ⁵ / cm ² or less, and a GaN film having extremely excellent crystallinity as compared with the conventional example of FIG. 36 can be obtained. I knew it was being done.
It was also found that the strain was different between the direction parallel to the stripe and the direction perpendicular to the stripe. That is, the element formation region 10
41 was found to have non-isotropic distortion.

In this embodiment, the case where the stripe of the amorphous GaN film 1035 is formed on the substrate has been described. However, the same effect can be obtained by using an oxide film layer such as a SiO ₂ film or a SiN film or a nitride film layer. Is obtained.

FIG. 38 shows an example in which this SiO ₂ film is used. On a substrate on which a stripe is formed by a SiO ₂ film 1038 having a thickness of 0.1 μm, G is formed in the same manner as in this embodiment.
Selective growth of the aN films 1033 and 1034 was performed. In this case, similarly, an epitaxial layer in which the strain due to the lattice mismatch was deviated in the direction parallel to the stripe was obtained. Furthermore, Ga
Since the N film does not grow on the SiO ₂ film (selective growth), the GaN film formed by this method has an island shape (island shape).
Will be formed. This island-like GaN film 1034
As for the state of distortion, the distortion remains in the direction parallel to the stripe,
Since the strain is relaxed in the direction perpendicular to the stripe, GaN
The film strain is reduced, and a non-isotropic strain state can be realized.

In this embodiment, the GaN epitaxial growth on the (0001) α-Al ₂ O ₃ (sapphire) substrate has been described. However, the present invention is not limited to this method. And any other lattice-mismatched epitaxial growth, and the same effect can be obtained.

In this embodiment, a plurality of stripes of the GaN film 1035 are formed.
Non-isotropic distortion of the GaN film in the element formation region can be realized. This is because non-isotropic distortion always exists near the stripe.

To grow a GaN film on a substrate,
Although the step growth method is used, the GaN film 1034 may be directly grown on the substrate without growing the GaN film 1033.

From the above, it can be seen that the method according to the present invention is sufficiently effective to obtain epitaxial growth characterized by concentrating lattice strain generated by lattice mismatch in a specific direction in epitaxial growth of a lattice mismatch system. ,
Proven.

Embodiment 14 A semiconductor light emitting device according to an embodiment of the present invention will be described with reference to the drawings. The feature of this embodiment is that a stress is physically applied to the side surface of the semiconductor light emitting device using a shape memory alloy, and a strain is introduced into the active layer.

As shown in FIG. 32, a shape memory alloy 14 having a concave portion 1403 and made of a Cu—Ni—Al alloy
04 is prepared. The width of the recess 1403 is 480 μm
Which is slightly smaller than the width of the semiconductor light emitting element. The surface of the recess 1403 is provided with a semiconductor light-emitting element, and is therefore subjected to a thin insulation treatment so that the light-emitting element is not short-circuited.

First, the concave portion 1403 is mechanically expanded. Then, a semiconductor light emitting element 1402 described later is set in this concave portion and put into a heating chamber. When the temperature is raised to 80 ° C. in this heating chamber, the shape memory alloy is also heated and returns to its original shape. By returning to the original recess,
A stress is applied to the semiconductor light emitting device 1402 in the x direction perpendicular to the stripe direction. As a result, strain is introduced in the uniaxial direction (the direction perpendicular to the stripe direction, that is, the x direction) in the c plane of the active layer. And the threshold current of the light emitting element can be reduced.

Since the size of the opening of the concave portion 1403 of the shape memory alloy is fixed to a predetermined size in advance, the stress applied to the light emitting element is also determined by the size of the opening. In addition, even if the concave portion is widened for mounting the light emitting element, it returns to the original state only by heating, so that mounting is easy. A semiconductor light-emitting device 1401 in which the semiconductor light-emitting element is mounted is referred to as a semiconductor light-emitting device 1401.

Next, the semiconductor light emitting device will be described. This light emitting device is manufactured by the following method using a metal organic chemical vapor deposition method.

First, a well-cleaned (0001) sapphire substrate (c-plane) is set on a susceptor in a reaction vessel, and the inside of the reaction vessel is set to a hydrogen atmosphere.
The temperature is raised to 0 ° C. to clean the substrate.

Subsequently, the temperature was lowered to 505 ° C., and 4 liters / minute of ammonia, 30 × 10 ⁻⁶ mol / minute of trimethylgallium as a raw material gas, and 2 liters / minute of hydrogen as a carrier gas were passed onto the substrate while flowing. Grow a GaN buffer layer.

Thereafter, the trimethylgallium was stopped, the temperature was raised to 1080 ° C., and trimethylgallium 50
X 10 ^-6 mol / min and silane gas at 2 X 10 ^-9 mol / min are flown to grow a silicon-doped n-type GaN layer.

After the growth of the n-type GaN layer, the source gas is stopped.
The substrate temperature was set to 800 ° C., the carrier gas was changed from hydrogen to nitrogen, nitrogen was 2 l / min, and the source gas was:
Trimethylgallium 2 × 10 ^-6 mol / min, 1 × 10 ^-5 mol / min trimethylindium, 2 × 10 ^-6 mol / min diethyl cadmium, reluctant raw flow 4 liters / min of ammonia, cadmium doped In _{A 0.14} Ga _0.86 N layer is grown.

After growing the cadmium-doped In _0.14 Ga _{0.86 N} layer, the source gas is stopped, the temperature is raised to 1080 ° C., trimethylgallium is 50 × 10 ⁻⁶ , and cyclopentadienyl magnesium is 3.6 × 10 ^−6. The p-type GaN layer is grown by flowing ammonia at a rate of 4 liters / min.

A part of the p-type GaN layer and the n-type InGaN layer of the semiconductor light emitting device obtained as described above is removed by etching to expose the n-type GaN layer, and the p-type GaN layer and the n-type GaN layer are removed. The layer was provided with p-type and n-type ohmic electrodes. This embodiment is mounted using this semiconductor light emitting device. The following embodiment is also mounted using this semiconductor light emitting device.

Embodiment 15 This embodiment is a semiconductor light emitting device in which a semiconductor light emitting element is mechanically stressed. This is a method of applying stress from the side to the semiconductor light emitting device shown in the fourteenth embodiment.

As shown in FIG. 33, in this semiconductor light emitting device, an AlGaInN-based crystal, which is a hexagonal compound semiconductor, is grown on the (0001) plane (c-plane). The stress is applied from the side surface of the semiconductor light emitting element in order to introduce the strain in the direction y)).

The semiconductor light emitting device 1502 is set in the stress applying container 1503, and the stress is gradually applied from the side thereof. The magnitude of the stress can be adjusted by turning the handle 1504.

In FIG. 33A, the semiconductor light emitting device 150
A sapphire substrate having a (0001) plane was used as the substrate of the second substrate.
When a semiconductor light emitting device in which an InN-based crystal is grown is used, as shown in FIG.
Direction). This is because even if strain is introduced in the c-axis direction, the valence band state density cannot be reduced, but if non-isotropic strain is introduced in the c plane, the valence band state density will be dramatically increased. It can be made smaller. If an R-plane is used for the substrate, the c-axis is oriented in the direction shown in FIG. 33 (b). Therefore, even if stress is applied perpendicularly (y-direction) to the substrate, non-isotropic strain is generated in the c-plane. It can be introduced. Of course, as described in (a) above, non-isotropic strain can be introduced in the c-plane by applying a stress from the side surface of the semiconductor light-emitting element grown on the R-plane.

According to the method of this embodiment, non-isotropic strain can be mechanically introduced into the c-plane of the semiconductor light emitting device, so that the state density of the valence band can be reduced and the threshold for laser oscillation can be obtained. The value current can be drastically reduced.

[0121]

As described above, according to the present invention, when a non-isotropic strain is applied to the c-plane of a hexagonal compound semiconductor, the effective mass of the hole near the upper end of the valence band is reduced. Based on the fact that the active layer is made smaller, the threshold current is increased by introducing non-isotropic (anisotropic) strain into the c-plane of the active layer composed of the hexagonal compound semiconductor grown in the c-axis direction. Semiconductor light-emitting element having a low level can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing an electronic band structure of a valence band of a GaN layer in an AlGaN / GaN quantum well.

FIG. 2 shows Al when non-isotropic strain is applied in the c-plane.
The figure which shows the electronic band structure of the valence band of a GaN layer in a GaN / GaN quantum well

FIG. 3 is a diagram showing the strain dependence of the threshold current density when non-isotropic (anisotropic) strain is applied to the c-plane.

FIG. 4 is a structural view of a semiconductor light emitting device according to one embodiment of the present invention.

FIG. 5 is a sectional view showing a manufacturing process of the semiconductor light emitting device according to one embodiment of the present invention.

FIG. 6 is a structural view of a semiconductor light emitting device according to one embodiment of the present invention.

FIG. 7 is a diagram showing the shape of a semiconductor light emitting device according to one embodiment of the present invention.

FIG. 8 is a structural view of a semiconductor light emitting device according to one embodiment of the present invention.

FIG. 9 is a process chart showing a method for manufacturing a semiconductor light emitting device according to one embodiment of the present invention.

FIG. 10 shows wurtzite InGaN /
Element cross section of AlGaN quantum well semiconductor laser

FIG. 11 shows two orthogonal crystal orientations on a LiTaO ₃ substrate.

FIG. 12 shows that the LiTaO ₃ substrate is moved from (1100) plane to (0
The figure showing the state inclined to the (001) direction or the (1120) direction.

FIG. 13 shows a wurtzite-type InGaN /
Element cross section of AlGaN quantum well semiconductor laser

FIG. 14 is a view showing a strain locally introduced around a p-Al _{z '} Ga ₁ -z'N strain introducing layer;

FIG. 15 is a comparison diagram of the thermal expansion coefficients of LiTaO ₃ and GaN.

FIG. 16 is a configuration perspective view showing a method for manufacturing a semiconductor laser according to an example of the present invention.

FIG. 17 is a structural view of a submount according to an embodiment of the present invention.

FIG. 18 is a configuration diagram showing a method for manufacturing a semiconductor laser according to another embodiment of the present invention.

FIG. 19 is a sectional view of a submount on which the semiconductor laser of the present invention is mounted.

FIG. 20 is a view of another submount for mounting the semiconductor laser of the present invention.

FIG. 21 is a sectional view showing the structure of a method for manufacturing a semiconductor laser according to another embodiment of the present invention.

FIG. 22 is a sectional view showing the structure of a semiconductor laser according to one embodiment of the present invention;

FIG. 23 is a view showing AlGa formed by a manufacturing method according to an embodiment of the present invention;
Manufacturing process diagram of InN-based semiconductor light emitting device

FIG. 24 is a view showing AlGa formed by a manufacturing method according to an embodiment of the present invention;
Manufacturing process diagram of InN-based semiconductor light emitting device

FIG. 25 is a diagram showing a process of vapor phase growth in which laser irradiation is selectively performed, and a diagram showing a relationship between lattice constants of a GaN crystal produced by a vapor deposition method in which laser irradiation is selectively performed.

FIG. 26 is a diagram showing a relationship between laser irradiation intensity and a GaN lattice constant.

FIG. 27 is a process chart of vapor phase growth in which laser irradiation is selectively performed.

FIG. 28 is a schematic cross-sectional view of a manufacturing step of a semiconductor device in Embodiment 11 of the present invention.

FIG. 29 is a schematic cross-sectional view of a semiconductor device and a schematic diagram of a crystal structure of an active layer according to an eleventh embodiment of the present invention.

FIG. 30 is a schematic view showing a manufacturing process of the semiconductor device according to Embodiment 12 of the present invention.

FIG. 31 is a schematic view of a unit cell of a GaN spiral thin film in Example 12 of the present invention.

FIG. 32 is a configuration perspective view of a semiconductor light emitting device according to Embodiment 14 of the present invention.

FIG. 33 is a configuration sectional view of a semiconductor light emitting device according to Embodiment 15 of the present invention.

FIG. 34 is a structural sectional view of a growth apparatus according to a thirteenth embodiment of the present invention.

FIG. 35 is a sectional view of a crystal growth step in Example 13 of the present invention.

FIG. 36 is a structural cross-sectional view after two-step growth in comparison with Example 13 of the present invention.

FIG. 37 is a structural perspective view after crystal growth in Example 13 of the present invention.

FIG. 38 is a structural sectional view when the SiO ₂ film of Example 13 of the present invention is used.

[Explanation of symbols]

REFERENCE SIGNS LIST 100 AlGaInN light emitting layer 101 sapphire substrate 102 striped groove 103 sapphire substrate 104 mask 105 groove 106 AlN buried layer 107 AlGaInN light emitting layer 108 sapphire substrate 109 oxide film 110 sapphire substrate 111 oxide film 112 SiC substrate 113 Ni layer 114 first Au layer 115 a second Au layer 116 AlGaInN light emitting element layer 117 sapphire substrate 118 stop jig 119 tray 201 LiTaO ₃ substrate 202 AlN buffer layer _{203 n-Al z Ga 1-} z n cladding layer 204 Al _y Ga _1-y n 1 the light guide layer _{205 In x Ga 1-x N} / GaN multi-quantum well active layer 206 Al _y Ga _1-y N second optical guide layer _{207 p-Al z Ga 1-} z N cladding layer 208 ridge stripe 209 SiO ₂ Absolute Enmaku 210 SiO ₂ insulating film opening 211 SiO ₂ insulating film opening 212 anode 213 cathode 301 (0001) sapphire substrate 302 AlN buffer layer _{303 n-Al z Ga 1-} z N cladding layer 304 Al _y Ga _1-y N first optical guiding layer _{305 In x Ga 1-x N} / GaN multi-quantum well active layer 306 Al _y Ga _1-y N second optical guide layer _{307 p-Al z Ga 1-} z N first cladding layer _{308 p-Al z 'Ga 1} -z' N strain induced layer _{309 p-Al z Ga 1-} z N second cladding layer 310 SiO ₂ insulating film 311 opening 312 opening 313 anode 314 cathode 401 semiconductor laser 402 submount 403 LiTaO ₃ 404 solder material 501 semiconductor laser 502 submount 503 Fe-Ni alloy 504 Fe- i-Mn alloy 505 Pb-Sn solder material 551 Semiconductor laser 552 Submount 553 Weighting collet 554 Ultraviolet curing resin 555 Submount 556 Weighting leaf spring 557 Weighting screw 601 6H-SiC substrate 602 AlN layer 603 AlN layer 604n -Type AlGaInN cladding layer 605 AlGaInN active layer 606 p-type AlGaInN cladding layer 607 p-side electrode 608 n-side electrode 651 6H-SiC substrate 652 AlN layer 653 AlN layer 654 n-type AlGaInN cladding layer 655 AlGaInN active layer 656 N-type AlGaInN cladding layer p-side electrode 658 n-side electrode 801 sapphire substrate 802 GaN crystal layer 803 GaN crystal layer 804 GaN crystal layer 805 GaN crystal layer 1011 Reaction tube 1012 Gas inlet tube 1013 Susceptor 1014 Sample substrate 1015 High frequency coil 1016 Thermocouple 1017 Gas inlet 1018 Vacuum pump 1031 Sapphire substrate 1032 Dislocation 1033 GaN epitaxial layer 1034 GaN epitaxial layer 1035 Amorphous GaN film 1036 Amorphous GaN film 1037 Interface 1038 SiO2 film 1039 Direction perpendicular to stripe 1040 Parallel direction to stripe 1041 Element formation region 1101 Sapphire substrate 1102 AlGaN cladding layer 1103 n-type AlInGaN cladding layer 1104 InGaN active layer 1105 p-type AlInGaN cladding layer 1106 Insulating film 1107 Schematic of lattice constant of active layer FIG. 1108 Schematic diagram of lattice constant of active layer 1201 Sapphire substrate 1202 aN crystal growth nucleus 1203 GaN spiral thin film layer 1204 GaN spiral thin film layer unit cell 1205 n-type AlGaN cladding layer 1206 InGaN active layer 1207 p-type AlGaN cladding layer 1401 semiconductor light emitting device 1402 semiconductor light emitting element 1403 recess 1404 shape memory alloy 1501 semiconductor light emitting device 1502 semiconductor light emitting element 1503 stress applying container 1504 handle

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kiyoji Onaka 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Akira Takamori 1006 Odaka Kadoma Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Masaya Manno 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Isao Kidoguchi 1006 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Hideto Adachi 1006 Kadoma Kadoma, Kadoma City, Osaka, Japan Inside Matsushita Electric Industrial Co., Ltd. (72) Inventor Akihiko Ishibashi 1006 Odaka Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (72) Toshiya Fukuhisa Osaka Matsushita Electric Industrial Co., Ltd., 1006 Kadoma, Kadoma, Futoma City In the business Co., Ltd. (56) references Jap J Appl Phys V ol. 27, No. 8, AUGUST, 1988, pp. L1384-L1386 (58) Field surveyed (Int. Cl. ⁶ , DB name) H01L 33/00

Claims (8)

(57) [Claims] 1. A semiconductor light emitting device in which an active layer is a hexagonal compound semiconductor and non-isotropic strain is present in a c-plane of the active layer. 2. The semiconductor light emitting device according to claim 1, wherein the active layer is grown in a c-axis direction. 3. The method according to claim 1, wherein the hexagonal compound semiconductor has a wurtz-type structure,
The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device has a 4H type structure or a 6H type structure. 4. The semiconductor light emitting device according to claim 1, wherein the non-isotropic strain is a uniaxial strain or a shear strain. Wherein said active layer is wurtzite Al _x Ga _y I
_nz N (however, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1)
The semiconductor light emitting device according to claim 1, wherein Wherein said active layer is formed on a sapphire substrate, the active layer is wurtzite Al _x Ga _y In
_2. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is formed of zN (where 0≤x≤1, 0≤y≤1, 0≤z≤1). 7. An active layer, which is a hexagonal compound semiconductor, having a c-axis direction.
And forming the active layer in the c-plane.
Semiconductor luminescence grown to introduce non-isotropic strain into the surface
Device manufacturing method. Wherein said active layer is wurtzite Al _x Ga _y I
n _z N (where, 0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ z ≦ 1)
The method for manufacturing a semiconductor light emitting device according to claim 7, wherein