JPH11297630A - Manufacture of crystal and light-emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystal whose crystalline defect density is smaller than a predetermined value by forming growth preventing materials on different surfaces in different mask patterns which are reverse to each other so as to prevent the growth of through dislocations. SOLUTION: A GaN layer 101 is grown on a sapphire substrate 100 by using trimethylgallium and ammonia and then a SiO2 film is formed in a periodic stripe pattern as a growth preventing material on the GaN layer 101 by a sputtering method to form a first patterned SiO2 mask 102. Next, a GaN crystal film 103 is grown by an organometallic vapor growth method and then a SiO2 film is formed in a periodic stripe pattern on the GaN crystal film 103 to form a second patterned SiO2 mask 104 having a reverse mask pattern of the first SiO2 mask 102. Further, a GaN single crystal film 105 is grown by the organometallic vapor growth method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a high-performance and highly-reliable device by growing high-quality crystals on substrates having different lattice constants and manufacturing light-emitting elements and electronic devices thereon. More particularly, the present invention relates to a crystal manufacturing method and a light emitting device for manufacturing a highly efficient and highly reliable gallium nitride (GaN) -based blue light emitting device.

[0002]

2. Description of the Related Art An opto-electric integrated circuit (OEIC) is a device for processing a large amount of information at a high speed by integrating an optical element and a Si-based LSI, and is expected to be an essential device in an advanced information society. Has been researched. In optical devices, the main purpose was to develop a technology for producing an AlGaAs laser on a Si substrate. However, AlGaAs crystal and S
Due to the large difference between the lattice constant and the coefficient of thermal expansion of the i-substrate, a high-quality AlGaAs crystal cannot be manufactured and has not been completed.

[0003] As Si-based LSIs, SOI and SIMOX have been proposed as ultrahigh-speed, low-power-consumption next-generation integrated circuits, and development has been rushed.

In gallium nitride (GaN) -based blue light-emitting devices, large bulk crystals cannot be obtained due to their large decomposition pressure. Therefore, GaN crystals are manufactured using a different material such as sapphire as a substrate.

In these substitute substrates, it is difficult to epitaxially grow a good crystal having a small crystal defect or a small crystal dislocation density directly on the substrate because of a large difference in lattice constant or thermal expansion coefficient from the nitride semiconductor. is there. For example, when a sapphire substrate is used as a substitute substrate for a nitride semiconductor (GaN), threading dislocations of 10 ⁹ to 10 ¹⁰ cm ⁻² exist in a nitride semiconductor (GaN) layer grown on the substrate. It is known to

As a solution to this problem, FIG. 7 shows the 58th Annual Meeting of the Japan Society of Applied Physics, 2p-Q-14, No. 1 (1
997) A first conventional example reported in p265 is shown.

In the figure, 700 is a sapphire substrate, 7
01 is an SiO ₂ pattern, 702 is an opening provided in SiO ₂ , and 703 is a GaN single crystal film grown by MOCVD. In the present embodiment, the GaN single crystal 70 on SiO ₂ is formed by using the growth suppressing effect by the SiO ₂ pattern such that the crystal growth starts from the opening.
Only in the case of No. 4, a defect density of 10 ⁵ to 10 ⁶ / cm ² was obtained, and the defect density was reduced by about four orders of magnitude compared with the above crystal without using the SiO ₂ pattern.

FIG. 8 shows the 58th Annual Meeting of the Japan Society of Applied Physics, 2p-Q-15, No. 1 (1997)
It is the second example reported in p.266. In the figure, 800 is a sapphire substrate, and 801 is a GaN single crystal grown by MOCVD. Reference numeral 802 denotes an SiO ₂ pattern, reference numeral 803 denotes an opening provided in the SiO _2, and reference numeral 804 denotes a GaN crystal grown by a hydride-VPE method. Also in this example, a defect density of 6 × 10 ⁷ / cm ² was obtained in the vicinity of the surface of the GaN crystal 804 grown by the hydride-VPE method, and the defect density was about three orders of magnitude lower than that of a conventionally obtained crystal. Reduced. By using such a GaN single crystal film shown in the conventional example as a substrate for growing a GaN-based semiconductor device, higher performance of an electronic device was expected.

[0009]

However, the quality of the obtained GaN single crystal substrate has not been sufficient even in the above-mentioned conventional example. For example, in the case of a semiconductor laser device, if there is no defect in the vicinity of the light emitting region, the life of the product is innovatively improved. For this purpose, a defect density of 10 ⁵ / cm ² or less is required. In this sense, the above-mentioned reduction of the defect density was insufficient. Desirably, a defect density of 10 ⁴ / cm ² or less similar to that of other III-V semiconductor substrates such as GaAs is required.

In the first conventional example, the high-quality crystal having a reduced defect density is limited to the SiO ₂ pattern, and the other regions have the same crystal quality as the conventional one. Was difficult to use.

In the second conventional example, a hybrid
By the -VPE method, a relatively thick film having a thickness of several tens of μm is grown as an epitaxially grown film, and the influence of the SiO ₂ pattern is reduced near the surface to uniformly distribute defects. However, the defect density was inferior to that of the first conventional example. An object of the present invention is to solve such a conventional problem.

[0012]

The crystal growth method according to the present invention (claim 1) uses a patterned mask made of a second growth-suppressing substance on different surfaces.

In the second patterned mask according to the present invention (claim 2), the light shielding portion is located above the crystal grown by the first patterned mask. In other words, the patterns of the first mask and the second mask are contradictory patterns.

The light shielding portion of the second mask according to the present invention (claim 3) is larger than the light opening portion of the first mask.

The second mask according to the present invention (claim 4) comprises two layers having different sizes.

The second mask according to the present invention (claim 5) has a lower portion on the first mask and is L-shaped. The lower portion of the second mask may be suspended from the substrate.

The second mask according to the present invention (claim 6) has a lower portion on the substrate and is T-shaped. Second
The lower portion of the mask may be suspended from the first mask.

In the crystal growth method according to the present invention (claim 7), the growth in the vertical direction is stopped by the mask immediately above the substrate, and the growth direction is changed.

In the crystal growth method according to the present invention (claim 8), the first crystal is grown only at the mask edge using the first mask.

The substrate according to the present invention (claim 9) uses sapphire.

The mask according to the present invention (claim 10) is S
iO ₂ or SiN _x is used.

The crystal according to the present invention (claim 11) is In
GaN and AlGaN.

A light emitting device according to the present invention (claim 12) is formed on the grown crystal.

[0024]

[Embodiment 1] A crystal growth method according to the present embodiment will be described with reference to FIG.

First, a GaN layer 101 is grown to a thickness of 4 μm on a sapphire substrate 100 having a C-plane as a surface by using trimethylgallium (TMG) and ammonia (NH ₃ ) as raw materials. Let it.

Next, in order to form a first patterned mask, a 200 nm thick SiO ₂ film was formed on the GaN layer 101 as a growth suppressing substance by a sputtering method.
The method for forming the SiO ₂ film is not limited to the sputtering method, but may be another method, for example, a vacuum deposition method or a CVD method.
In addition, as a growth suppressing substance, other than SiO ₂ , Al
Oxides such as ₂ O ₃ and TiO ₂ and SiN _x may be used. Then
The first SiO ₂ mask 102 was formed by using a regular photoresist method to form the SiO ₂ film into a periodic stripe pattern having a stripe width of 7 μm and a pitch of 10 μm. The direction of the stripe was desirably the <1-100> direction of the crystal of the GaN layer 101.

Using such a substrate, a GaN crystal film 103 was grown by MOVPE (metal organic chemical vapor deposition). Trimethyl gallium (TMG) in a given growth furnace
And ammonia (NH ₃ ) as raw materials, at a growth temperature of 10
A GaN crystal film 103 having a thickness of 3 μm was grown at 50 ° C. The GaN crystal film 103 began to grow from the opening of the first mask, and grew smoothly over substantially the entire surface of the substrate due to anisotropy that the growth rate was higher in the horizontal direction than in the vertical direction.

However, the defect density was 10 ⁵ / cm ² or less directly above the first mask, but was still 10 ⁷ / cm ² immediately above the sapphire substrate at the mask opening.
m ² . In the conventional example, the laser element was formed avoiding such a place, but was insufficient in reliability and yield.

Next, a second layer is formed on the GaN crystal film 103.
Was formed. A 200 nm thick SiO ₂ film is formed by a sputtering method in the same manner as the first mask formation, and a stripe width of 8 μm and a pitch of 10 μm by a photoresist method.
The second SiO ₂ mask 104 was formed in the form of a periodic stripe pattern. At this time, it is important that the position of the second mask substantially coincides with the opening of the first mask.

Next, using such a substrate, MOV
GaN single crystal film 105 by PE method (metal organic chemical vapor deposition)
Grew. GaN having a thickness of 3 μm was grown at a growth temperature of 1050 ° C. using trimethylgallium (TMG) and ammonia (NH ₃ ) as raw materials in a predetermined growth furnace.
In the GaN single crystal film 105 thus grown, the defect density was reduced to 1500 / cm ² or less over the entire surface, and the crystallinity was extremely improved.

In the above embodiment, both the first mask and the second mask have a stripe width of 4 μm and a pitch of 10 μm.
When the masks are arranged at positions shifted from each other by a half pitch (when the second mask width is smaller than the lacking portion of the first mask), the defect density becomes 5000 defects / cm ² , and the conventional first mask Compared with the case of only, a sufficient effect of reducing crystal defects was observed. The effect of this reduction is that the second mask width is larger than the lack of the first mask, and the two masks completely cover the crystal dislocations extending directly above the sapphire substrate 100. The density has increased, and it has been confirmed that it is important to form the second mask so as to completely cover the missing portion of the first mask.

However, when the width of the second mask is smaller than the missing portion of the first mask, the effect of reducing defects to some extent (about 5000 / cm ² ) and the c-axis orientation of the GaN continuous film are improved. This was found by X-ray diffraction measurement. When the width of the second mask is larger than the missing portion of the first mask, the ω value (half width) of X-ray diffraction indicating the variation of the orientation is about 4 to 6 minutes. It was confirmed that the use reduced the variation (ω value) of the crystal orientation in the wafer plane to 2 minutes. Therefore, when an LED or a semiconductor laser is manufactured in a shape in which the second mask width is smaller than the lacking portion of the first mask, light emission is larger than when the second mask width is larger than the lacking portion of the first mask. Although the efficiency was somewhat inferior, it was found that the luminous efficiency in the wafer surface and the uniformity of the threshold current of the laser were improved, and the production yield of the device could be improved. Therefore, it is important to select the relationship between the lack of the first mask and the width of the second mask in accordance with the required characteristics of the light emitting element. In addition, the first mask and the second mask
If the masks are formed of the same material, the vapor deposition apparatus can be unified, and the quality of the crystal film can be stabilized by the same growth suppression effect. Select the width of the second mask larger than the missing part,
When giving priority to uniformity of characteristics and yield, the width of the second mask should be selected to be smaller than that of the first mask.)

[Embodiment 2] FIG. 2 shows a second embodiment. The GaN crystal film 203 grown using the first mask is not a continuous film,
The only difference is that this mask is formed on the upper surface of the GaN crystal film 203 grown like an island.

First, a GaN layer 201 is grown on a sapphire substrate 200 by 4 μm in the same manner as in the first embodiment. In the case of the second embodiment, first GaN crystal film 203 grown using first SiO ₂ mask 202 has a thickness of 1 μm.
m, width 7 μm, and pitch 10 μm. Next, a second SiO ₂ mask 204 (200 μm thick) is used
When the GaN single crystal film 205 (thickness) was grown, the defect density was 800 / cm ² or less, and a good crystal was obtained. This is because the GaN single crystal film 205 is the first GaN
This is an effect of growing only from the side surface 206 having few crystal defects.

[Embodiment 3] A second embodiment will be described with reference to FIG. In the first embodiment, the crystal growth of GaN on the patterned mask had to be performed in two steps. However, in the present invention, only one time was required, which is advantageous in cost. First, the sapphire substrate 3 on which the GaN layer 301 is formed
In the same manner as in the first embodiment, a 200 nm thick SiO ₂ film is formed by sputtering. This is etched in a stripe pattern with a width of 4 μm and a pitch of 8 μm by a normal photoresist method,
A first SiO ₂ mask 302 is manufactured. Next, an SiO ₂ film is similarly formed on such a substrate, and a second lower SiO ₂ mask 303 having a stripe shape with a width of 2 μm and a pitch of 8 μm is formed on the first mask. Next, a portion other than the lower SiO ₂ mask 303 is covered with a photoresist film by a usual photolithography method. According to this method, a photoresist such as AZ of Shipley is spin-coated on the entire surface, and the lower S
Only the 303 portion of the iO ₂ mask may be exposed and developed to remove the resist film. Further, a _second upper SiO ₂ mask 3 in the form of a stripe having an SiO ₂ film formed thereon and having a width of 5 μm and a pitch of 8 μm is formed.
04 is formed. Thereafter, the above-mentioned photoresist film is removed with a solvent such as acetone. The second lower SiO ₂ mask 303 and the second upper SiO ₂ mask 304
L-shaped. GaN was grown by MOVPE using such a substrate. A 3 μm thick GaN single crystal film 305 was grown at a growth temperature of 1050 ° C. using trimethylgallium (TMG) and ammonia (NH ₃ ) as raw materials in a predetermined growth furnace. The growth starts from the opening of the first SiO ₂ mask 302, the growth in the second upper SiO ₂ mask 304 stops in the direction perpendicular to the substrate, and then grows in the direction parallel to the substrate to form the second upper S 2.
Growth started in the direction perpendicular to the substrate from the opening of the iO ₂ mask 304, and finally it grew uniformly over the entire surface of the substrate. Dislocations generated from the interface between the GaN layer 301 and the sapphire substrate 300 in the direction perpendicular to the substrate are caused by the second upper S
The dislocation in the direction parallel to the substrate is stopped by the iO ₂ mask 304, and is stopped by the second lower SiO ₂ mask 303. Therefore, the obtained GaN single crystal film 305 was of very good quality with a defect density of 600 / cm ² or less.

Fourth Embodiment A fourth embodiment will be described with reference to FIG. First, a 200 nm thick SiO ₂ film is formed on the sapphire substrate 400 on which the GaN layer 401 is formed by the sputtering method as in the first embodiment. This is etched in a stripe shape with a width of 4 μm and a pitch of 8 μm by a normal photoresist method to produce a first SiO ₂ mask 402. Next, the second lower SiO ₂ having a width of 2 μm and a pitch of 8 μm is formed on the GaN layer 401 by using the same method as described above.
The mask 403 is formed in a stripe shape. Next, a portion other than the lower SiO ₂ mask 403 is covered with a photoresist film by a usual photolithography method. In this method, a photoresist such as AZ of Shipley is spin-coated on the entire surface,
It is sufficient to expose and develop only the lower SiO ₂ mask 403 to remove the resist film. Further, the second upper SiO ₂ mask stripe width 5μm pitch 8μm of SiO ₂ 40
4 is formed on the second lower SiO ₂ mask 403. Thereafter, the above-mentioned photoresist film is removed with a solvent such as acetone. This mask 2nd lower SiO ₂ mask 4
03 and the second upper SiO ₂ mask 404 form a T-shape as a second mask. GaN was grown by MOVPE using such a substrate. Trimethyl gallium (TMG) and ammonia (NH
_{Using 3} ) as a raw material, a growth temperature of 1050 ° C. and a thickness of 3 μm
GaN single crystal film 405 was grown. Growth is the first S
Starting from the opening in the iO ₂ mask 402, the second upper S
The growth in the direction perpendicular to the substrate is stopped by the SiO ₂ mask 404,
Thereafter, the substrate was grown in a direction parallel to the substrate, and began to grow also in the direction perpendicular to the substrate from the opening of the second upper SiO ₂ mask 404, and finally, uniformly grown over the entire surface of the substrate. Ga
Dislocations generated from the interface between the N layer 401 and the sapphire substrate 400 in the direction perpendicular to the substrate are stopped by the second upper SiO ₂ mask 404 immediately above, and dislocations in the direction parallel to the substrate are stopped by the second lower SiO ₂ mask 403. Stop by Therefore,
The obtained GaN single crystal film 405 has a defect density of 800 / cm.
Very good quality of ² .

[Fifth Embodiment] A fifth embodiment will be described with reference to FIG. First, in order to form a first patterned mask, a 200-nm-thick SiO ₂ film was formed by a sputtering method on a sapphire substrate 500 having a C-plane on which a GaN layer 501 was formed as a surface. . The method for growing the SiO ₂ film is not limited to the sputtering method, but may be another method such as a vacuum evaporation method or a CVD method. Further, as a growth suppressing substance, other than SiO ₂ , Al ₂
An oxide such as O ₃ or TiO ₂ or SiN _x may be used. Then
An opening was formed in the form of a stripe of SiO ₂ film having a width of 3 μm and a pitch of 100 μm by an ordinary photoresist method, and a first SiO ₂ mask 502 was formed. The desired direction of the stripe was <1-100> for the GaN layer 501.

Using such a substrate, GaN was grown by MOVPE. GaN having a thickness of 0.5 μm was grown at a growth temperature of 1050 ° C. using trimethylgallium (TMG) and ammonia (NH ₃ ) as raw materials in a predetermined growth furnace. The GaN 503 grew only at the edge of the first mask and did not fill the first SiO ₂ mask 502. Since this edge portion is a peculiar point having a low potential for crystal growth, the GaN 503 was of very good quality without defects.

Next, a second mask was formed on such a substrate. 20 with the same sputtering method as the first mask formation.
A SiO ₂ layer having a thickness of 0 nm is formed, and the second Si layer is formed into a stripe shape with a width of 5 μm and a pitch of 100 μm by a photoresist method.
An O ₂ mask 504 was formed. It is important that the position of the light-shielding portion be substantially coincident with the opening of the first mask.

Next, using such a substrate, MOV
A GaN single crystal film 505 was grown by the PE method. GaN having a thickness of 3 μm was grown at a growth temperature of 1050 ° C. using trimethylgallium (TMG) and ammonia (NH ₃ ) as raw materials in a predetermined growth furnace. G grown in this way
The aN single crystal film 505 has a defect density of 100 over the entire surface.
The number was reduced to 0 / cm ² or less, and the crystallinity was extremely improved.

Here, it is important that the light-shielding portion of the second mask covers the opening of the first mask.

[Sixth Embodiment] A sixth embodiment will be described with reference to FIG. FIG. 6 shows that the sapphire substrate 600 to the GaN single crystal film 605 according to the embodiment of the present invention is replaced by the sapphire substrate 100 described in the first embodiment.
This corresponds to the N single crystal film 105.

In this figure, 606 is an n-GaN contact layer, 607 is an n-Al _0.1 Ga _0.9 N cladding layer, 608
Is an n-GaN guide layer, and 609 is five layers of In _0.2 Ga _0.8
An active layer having a multiple quantum well structure including an N quantum well layer and six In _0.05 Ga _0.95 N barrier layers, and 610 is an Al _0.2 Ga _0.8 N
Evaporation prevention layer, 611 is a p-GaN guide layer, 612 is p
-Al _0.1 Ga _0.9 N clad layer, 613 is a p-GaN contact layer, 614 is a p-type electrode, 615 is an n-type electrode, 6
Reference numeral 16 denotes a SiO ₂ insulating film.

In the present invention, the surface of the sapphire substrate 600 may have another plane orientation such as a plane, r plane, or m plane. Moreover, not only sapphire substrate but also GaN substrate, Si
C substrate, spinel substrate, MgO substrate, Si substrate, GaAs
An s substrate can also be used. In particular, in the case of a GaN substrate, a good crystalline film having a small difference in lattice constant from a gallium nitride-based semiconductor material deposited on the substrate compared to a sapphire substrate can be obtained. There is an advantage that the container can be easily formed. The n-type cladding layer and the p-type cladding layer are made of Al _0.1 Ga _0.9 N
AlGaN ternary mixed crystals having Al compositions other than the above may be used. In this case, when the Al composition is increased, the energy gap difference and the refractive index difference between the active layer and the cladding layer increase,
Carriers and light are confined in the active layer, so that the oscillation threshold current can be further reduced and the temperature characteristics can be improved. Further, when the Al composition is reduced to such an extent that the confinement of carriers and light is maintained, the mobility of carriers in the cladding layer increases, and thus there is an advantage that the device resistance of the semiconductor laser device can be reduced. Further, these cladding layers may be quaternary mixed crystal semiconductors containing trace amounts of other elements.
_0.1 Ga _0.9 N cladding layer 607 and p-Al _0.1 Ga _0.9 N
The composition of the mixed crystal in the cladding layer 612 may not be the same.

The energy gaps of the n-GaN guide layer 608 and the p-GaN guide layer 611 are the same as the energy gap of the quantum well layer forming the multiple quantum well structure active layer 609 and the n-Al _0.1 Ga _0.9 N clad layer 607. ,
As long as the material has a value between the energy gaps of the p-Al _0.1 Ga _0.9 N cladding layer 612, other materials such as InGaN and AlGaN ternary mixed crystal may be used instead of GaN. Further, it is not necessary to dope the entire guide layer with the donor or acceptor, and only a part of the multiple quantum well structure active layer 609 side may be non-doped, and further, the entire guide layer may be non-doped. In this case, there are advantages that the number of carriers existing in the guide layer is reduced, light absorption by free carriers is reduced, and the oscillation threshold current can be further reduced.

The composition of the In _0.2 Ga _0.8 N quantum well layer and the In _0.05 Ga _0.95 N barrier layer constituting the multi quantum well structure active layer 609 may be set according to the required laser oscillation wavelength. If you want to make it longer, I
To increase and shorten the n composition, the In of the quantum well layer
Reduce composition. The quantum well layer and the barrier layer are made of InGa.
A quaternary or higher mixed crystal semiconductor containing a trace amount of another element in an N ternary mixed crystal may be used. Further, the barrier layer may simply use GaN.

In this embodiment, the Al _0.2 Ga _0.8 N evaporation preventing layer 610 is formed in contact with the multiple quantum well structure active layer 609. This is to prevent evaporation during the ascent. Therefore, as long as it protects the multi-quantum well structure active layer, it can be used as the Al _0.2 Ga _0.8 N evaporation preventing layer 610, and an AlGaN ternary mixed crystal having another Al composition or GaN may be used. The Al _0.2 Ga _0.8 N evaporation preventing layer 610 may be doped with Mg. In this case, the p-GaN guide layer 6
There is an advantage that the holes from 11 and p-Al _0.1 Ga _0.9 N cladding layer 612 are easily injected. Further, when the In composition of the quantum well layer constituting the multiple quantum structure active layer is small, the quantum well layer does not evaporate without forming the Al _0.2 Ga _0.8 N evaporation preventing layer 610.
_{Even if the 0.2} Ga _0.8 N evaporation preventing layer 610 is not formed, the characteristics of the gallium nitride based semiconductor laser device of the present embodiment are not impaired.

Next, a method for manufacturing the above gallium nitride based semiconductor laser will be described with reference to FIG. In the following description,
Although the case where the MOVPE method is used is shown, a growth method capable of epitaxially growing GaN may be used.
Other vapor phase growth methods such as HVPE and HVPE can also be used.

First, a trimethylgallium (TMG) was set on a substrate and set on a substrate, which was prepared in the first embodiment.
And ammonia (NH ₃ ) and silane gas (SiH ₄ ) as raw materials, a growth temperature of 1050 ° C. and a thickness of 3 μm of Si.
A n-GaN contact layer 606 doped with is grown. Further, trimethyl aluminum (TMA)
Was added to the raw material, and 0.4 μm
The n-Al _0.1 Ga _0.9 N cladding layer 607 is grown. Subsequently, an n-GaN guide layer 608 doped with Si and having a thickness of 0.1 μm is grown at a growth temperature of 1050 ° C., excluding TMA from the raw material.

Next, the growth temperature was lowered to 750 ° C.
Using G, NH ₃ , and trimethylindium (TMI) as raw materials, an In _0.05 Ga _0.95 N barrier layer (5 nm in thickness)
/ In _0.2 Ga _0.8 N quantum well layer after (thick 2 nm) of 5 cycles growth, In _{0. 05} Ga _0.95 N barrier layer (thickness 5 nm)
Is grown to form a multiple quantum well structure active layer 609.
(Total thickness of 40 nm). Further, using TMG, TMA and NH ₃ as raw materials, the growth temperature was 7
At 50 ° C., an Al _0.2 Ga _0.8 N evaporation preventing layer 610 having a thickness of 20 nm is grown.

Next, the growth temperature was raised again to 1050 ° C., and TMG, NH ₃ , and bisethylcyclopentadienyl magnesium (FtCp ₂ Mg) were used as raw materials to form a 0.1 μm-thick Mg-doped p-type. -GaN guide layer 6
Grow 11 Subsequently, TMA is added to the raw material, and a 0.4 μm-thick Mg-doped p-Al _0.1 Ga _0.9 N clad layer 612 is grown at a growth temperature of 1050 ° C.
Subsequently, TMA was removed from the raw material, and the growth temperature was 1050.
P-Ga doped with 0.2 μm thick Mg
The gallium nitride based epitaxial wafer is completed by growing the N contact layer 613. Thereafter, the wafer is annealed in a nitrogen gas atmosphere at 800 ° C. to reduce the resistance of the Mg-doped p-type layer.

Further, using the usual photolithography and dry etching techniques, a 200 μm-width stripe is formed from the outermost surface of the p-GaN contact layer 613 to n.
Etching until the GaN contact layer 606 is exposed to form a mesa structure; Next, the remaining p-GaN contact layer 613 and p-Al _0.1 Ga _0.9 are formed by using the same photolithography and dry etching technology as described above.
The N cladding layer 612 is etched. At this time, the stripe-shaped ridge structure may be separated by 3 μm or more from both ends of 200 μm. In this embodiment, the n-type electrode 615 is used.
A stripe-shaped ridge structure was formed at a distance of 10 μm from the end of the mesa structure on the side where the ridge was formed. Thus n
When a stripe-shaped ridge structure is arranged close to the mold electrode 615, the electric resistance of the element is reduced and the operating voltage is reduced. In addition, since the etching is stopped so as not to reach the multiple quantum well structure active layer 609 at the time of the dry etching sig, etching damage to the active layer is suppressed, thereby lowering the reliability and oscillating threshold current. Is prevented from increasing.

Subsequently, a 200 nm thick SiO ₂ insulating film 616 is formed as a current blocking layer on the side surfaces of the ridge and on the surface of the p-type layer other than the ridge. This SiO ₂ insulating film 616 and p
Forming a p-type electrode 614 made of nickel and gold on the surface of the GaN contact layer 613 and forming an n-type electrode 615 made of titanium and aluminum on the surface of the n-GaN contact layer 606 exposed by etching; Complete system LD wafer.

Thereafter, the wafer is cleaved in a direction perpendicular to the ridge stripe to form a laser resonance surface, and further divided into individual chips. Then, each chip is mounted on a stem, each electrode is connected to a lead terminal by wire bonding, and a gallium nitride based semiconductor laser device is completed.

The semiconductor laser device manufactured as described above had good laser characteristics of an oscillation wavelength of 410 nm and an oscillation threshold of 20 mA. Further, the decrease of the crystal defects was high laser device extremely reliable and 10 ⁵ hours (60 ° C.). Further, the ratio of the laser element having a crystal defect was extremely reduced, and an element yield of 80% or more was obtained.

In the present embodiment, the thicknesses of the quantum well layer and the barrier constituting the multi-quantum well structure active layer 609 are set to 2 nm and 5 nm, respectively. Then, regardless of the present embodiment, the same effects can be obtained with other layer thicknesses. The number of quantum well layers of the multiple quantum well structure active layer 609 may be four or three, or may be a single quantum well structure active layer.

Further, in this embodiment, since sapphire, which is an insulator, is used as the substrate, the n-type electrode 615 is formed on the surface of the n-GaN contact layer 606 exposed by etching. Having GaN,
If SiC, Si, GaAs, or the like is used, the n-type electrode 615 may be formed on the back surface of the substrate. In this case, 200
The μm-wide stripe-shaped ridge structure may be separated from the two ends of the semiconductor laser element chip by 3 μm or more. Also,
The p-type and n-type configurations may be reversed.

[0058]

As described above, in the gallium nitride crystal according to the present invention, a substance having a growth suppressing effect is formed on a different surface with a reverse mask pattern so as to prevent the growth of threading dislocations, thereby obtaining a crystal defect. Crystals having a very small density of 10 ⁴ cm ² or less were obtained. A gallium nitride semiconductor laser manufactured using such a crystal has high reliability, has a very high yield, and can be produced at low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a gallium nitride semiconductor substrate showing a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a gallium nitride semiconductor substrate according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of a gallium nitride semiconductor substrate showing a third embodiment of the present invention.

FIG. 4 is a cross-sectional view of a gallium nitride semiconductor substrate showing a fourth embodiment of the present invention.

FIG. 5 is a cross-sectional view of a gallium nitride semiconductor substrate showing a fifth embodiment of the present invention.

FIG. 6 is a cross-sectional view of a gallium nitride semiconductor substrate according to a sixth embodiment of the present invention.

FIG. 7 is a sectional view showing a GaN crystal film according to a first conventional example of the present invention.

FIG. 8 is a sectional view showing a GaN crystal film according to a second conventional example of the present invention.

[Explanation of symbols]

100, 200, 300, 400, 500, 600 Sapphire substrate 101, 201, 301, 401, 501, 601 G
aN layer 102, 202, 302, 402, 502, 602 First SiO ₂ mask 103, 203, 603 GaN crystal film 104, 204, 504 Second SiO ₂ mask 105, 205, 305, 405, 505, 605 G
aN single crystal film 206 GaN crystal film 203 Side surface 303, 403 of crystal, second lower SiO ₂ mask 304, 404 second upper SiO ₂ mask 503 GaN 604 second SiO ₂ mask 606 n-GaN contact layer 607 n -Al _0.1 Ga _0.9 N cladding layer 608 n-GaN guide layer 609 Multiple quantum well structure active layer 610 Al _0.2 Ga _0.8 N evaporation preventing layer 611 p-GaN guide layer 612 p-Al _0.1 Ga _0.9 N cladding layer 613 p-GaN grown in the contact layer 614 p-type electrode 615 n-type electrode 616 SiO ₂ insulating film 700, 800 sapphire substrate 701,802 SiO ₂ pattern 702,803 openings 703 GaN single crystal 801 MOCVD method on a GaN single crystal film 704 SiO ₂ GaN single crystal 804 Hydride GaN grown by VPE method
crystal

Claims (12)

[Claims] 1. A method of manufacturing a crystal using a substrate on which a first patterned mask made of a substance having a growth suppressing effect is formed, wherein a substance having a growth suppressing effect is formed on a surface different from the first patterned mask. Using a second patterned mask comprising: growing a crystal continuously from said crystal. 2. The method according to claim 1, wherein the second patterned mask is formed on top of the crystal grown using the first patterned mask. 3. The method according to claim 1, wherein the second patterned mask is larger than the first patterned mask.
The method for producing a crystal according to any one of the above. 4. The method according to claim 1, wherein the second patterned mask has two different widths.
The method for producing a single crystal according to claim 1, wherein the single crystal has a structure composed of layers. 5. The method according to claim 4, wherein a lower layer of the second patterned mask is at least above the first patterned mask and is L-shaped. 6. The method according to claim 4, wherein the lower layer of the second patterned mask is at least on the substrate and is T-shaped. 7. The crystal manufacturing method according to claim 1, wherein the crystal growth is stopped immediately above the substrate and the direction of growth is changed. 8. The crystal manufacturing method according to claim 1, wherein the crystal is grown only on the edge of the mask using the first patterned mask. 9. The method for producing a crystal according to claim 1, wherein the substrate is sapphire. 10. The method according to claim 1, wherein the mask is made of SiO ₂ or SiN _x . 11. The crystal to be manufactured is InGaN, AlGa
The method for producing a crystal according to claim 1, wherein N is N. 12. A light-emitting element using a substrate manufactured by using the method of manufacturing a crystal according to claim 1.