JP2000252219A - PRODUCTION OF GaN SUBSTRATE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a GaN substrate in which crystal defect is suppressed by growing a second nitride semiconductor and removing at least up to a different kind of substrate and then growing a third nitride semiconductor on the second nitride semiconductor thereby suppressing warp during production. SOLUTION: A second nitride semiconductor 3 is grown by HVPE on a first epitaxially grown nitride semiconductor layer 2. It is then polished from the side where a different kind of substrate 1 is exposed thus removing the second nitride semiconductor 3 at least up to the different kind of substrate 1. When the different kind of substrate 1 is removed by polishing, stress dependent on the different kind of substrate will depend on the nitride semiconductor and a significantly warped nitride semiconductor is obtained at the stage where the different kind of substrate 1 is removed entirely. Subsequently, a third nitride semiconductor 4 is grown on the nitride semiconductor by HVPE. When a thick film of third nitride semiconductor 4 is formed by HVPE, a GaN substrate where warp is suppressed can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates, for example, LED (light emitting diode), LD (laser diode) nitride such as semiconductor _{(In X Al Y Ga 1-} XY N, 0 ≦ X, 0 ≦ Y, X + Y
<1) The present invention relates to a method for manufacturing a GaN substrate used in <1).

[0002]

2. Description of the Related Art The applicant of the present invention has realized various kinds of layer structures laminated on a nitride semiconductor substrate, for example, a light emitting diode (LED) having a high luminance such as blue light, and a continuous oscillation for a long time at room temperature. A nitride semiconductor device such as a blue laser diode (LD) has been realized. Further, the use of the nitride semiconductor is not limited to this, and the use of the nitride semiconductor to other nitride semiconductor devices has been proposed, and intensive research has been conducted by various research institutions.

[0003] Such a nitride semiconductor is obtained by stacking various layers on a nitride semiconductor layer generally formed on a heterogeneous substrate represented by sapphire as a substrate. Are manufactured. As a specific example of a light-emitting element, an n-layer and a p-layer are stacked after a nitride semiconductor layer is epitaxially grown on a sapphire substrate, and electrodes corresponding to the respective layers are provided.

As described above, the demand for realizing the production of a nitride semiconductor substrate lattice-matched with a nitride semiconductor is only increasing, but the GaN bulk crystal is taken as an example and various research institutions have tried it. Regardless, only a few mm are reported.

[0005] As a method of manufacturing a nitride semiconductor substrate,
JP-A-7-20226 discloses a method of forming an intermediate layer of zinc oxide on a sapphire substrate, laminating a nitride semiconductor, and peeling the intermediate layer from the sapphire substrate by wet etching.
No. 5 discloses this. However, a nitride semiconductor layer having good crystallinity could not be obtained with the nitride semiconductor layer obtained by this method. However, when the GaN single crystal sapphire substrate is thinned, stress is generated due to lattice mismatch between the sapphire substrate and GaN, and the substrate is warped.
There has been a limit in obtaining a good nitride semiconductor device by forming a nitride semiconductor on this substrate.

Japanese Patent Application Laid-Open No. H11-1399 discloses a method in which GaN is formed on an oxide substrate and then polished from the sapphire substrate to only GaN. In this method, GaN is grown on an oxide substrate and HV is grown.
A primary GaN having a certain thickness is formed by the PE method, a nitride semiconductor substrate on which the primary GaN layer is grown is polished to remove a part of the oxide substrate, and a primary GaN layer is formed on the primary GaN layer. A secondary GaN layer is then grown and polished and removed again to remove the primary and secondary Ga from which the nitride semiconductor substrate has been completely removed.
A GaN layer having a predetermined thickness is grown again on the N layer to form a GaN layer.
A single crystal is grown, and finally a GaN single crystal is polished to
Obtain an N substrate. However, the GaN substrate obtained by this method has very many defects, and even if a nitride semiconductor is produced using this substrate, an element having good characteristics cannot be obtained, and a nitride semiconductor laser element having a complicated layer structure has been obtained. Did not even oscillate.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and a warp that occurs during fabrication of a GaN substrate in which a nitride semiconductor is stacked on a GaN substrate to form a nitride semiconductor device. It is an object of the present invention to provide a method of manufacturing a GaN substrate having reduced crystal defects and having very few crystal defects, and to obtain a nitride semiconductor device having good device characteristics with a high yield.

[0008]

The present inventor studied the GaN substrate to achieve the above object. As a result, after forming GaN in a thick film on the sapphire substrate, the GaN substrate was polished from the sapphire substrate side. If only GaN is used, warpage occurs. However, by laminating GaN with a thicker film on this GaN substrate, strain stress caused by lattice mismatch between sapphire and GaN is alleviated, and good warpage with reduced warpage is achieved. We succeeded in obtaining a GaN substrate.

Further, since the GaN substrate obtained by the manufacturing method of the present invention is manufactured using laterally grown GaN, a GaN substrate having very few crystal defects can be obtained as a relatively thick film. Since a resonance surface can be formed by cleavage, it is particularly useful for manufacturing a nitride semiconductor laser device having a complicated layer structure.

That is, the present invention relates to a method of manufacturing a GaN substrate which is a nitride semiconductor device by laminating a nitride semiconductor on a GaN substrate, and includes GaN by lateral growth on a substrate different from the nitride semiconductor. A first step of growing a first nitride semiconductor layer, a second step of growing a second nitride semiconductor thereon, and a third step of removing at least a heterogeneous substrate after the second step. And a fourth step of growing a third nitride semiconductor on the second nitride semiconductor after the third step.

In the first step, after growing GaN on a heterogeneous substrate, irregularities are formed on the surface of the GaN, and GaN is grown substantially laterally at least over the surface from the concave portion to the convex portion. It is characterized by the following.

After the fourth step, there is provided a fifth step of removing part or all of the second nitride semiconductor or part of the third nitride semiconductor from the side from which the heterogeneous substrate is removed. It is characterized by.

The thickness of the second nitride semiconductor layer is 10
The thickness is adjusted to not less than 400 μm and not more than 400 μm, and the thickness of the third nitride semiconductor layer is not less than 100 μm and not more than 40 μm.
It is characterized in that it is adjusted to 0 μm or less.

Further, the first step is characterized in that the nitride semiconductor is grown by the MOVPE method, and the second step and the fourth step are grown by the HVPE method.

After the fifth step, the GaN substrate is polished to a thickness of 100 μm or more and 300 μm or less, and a device structure is formed thereon. By setting the total thickness of a GaN substrate having a structure of three or more layers in this range, the characteristics of a nitride semiconductor device obtained by laminating a nitride semiconductor thereon are improved.

The different substrate different from the nitride semiconductor is C
It is characterized by using a sapphire substrate that is off-angled with respect to the surface.

The second nitride semiconductor layer and / or the third nitride semiconductor layer is doped with Si or Sn.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. 1 to 6 are schematic views showing specific examples of the production method of the present invention. First, as a first step, as shown in FIG.
An underlayer of a nitride semiconductor is grown on a heterogeneous substrate 1 different from a nitride semiconductor such as a sapphire substrate by the MOVPE method, this is referred to as a first layer, and then a nitride semiconductor is formed by epitaxial growth. Epitaxial growth refers to the growth of a single crystal with few crystal defects. In particular, in the case of nitride semiconductors, the crystal defects are prevented from growing in the thickness direction by performing selective growth (lateral growth) in the direction transverse to the thickness direction. It is known that a good epitaxial growth layer can be obtained.

More specifically, as a method of performing lateral selective growth (lateral growth), a first layer made of GaN is formed, and the first layer is partially formed with irregularities (2a).
A surface capable of laterally growing the nitride semiconductor is exposed on the side surface of the concave portion, and the nitride semiconductor is grown thereon (2b).

Other methods for lateral growth include
Is SiO 2 on a nitride semiconductor layer made of GaN._TwoEtc.
A mask is partially formed (for example, in a stripe shape), and
Next, a nitride semiconductor is grown. Either way
Nitride semiconductors grow laterally, both of which have crystal defects.
Although a small number of epitaxially grown layers is always obtained,
_TwoFor the mask material, etc., the nitride semiconductor is a good single crystal.
Decomposes at a temperature obtained, for example, at a temperature of 1000 ° C. or higher.
Cause abnormal growth of nitride semiconductors
The method of forming the irregularities will make
It is preferred to grow.

In addition, a heterogeneous substrate 1 different from the nitride semiconductor
Is sapphire including C-plane, R-plane and A-plane, an insulating substrate such as spinel (MgAl ₂ O ₄ ), SiC (6H,
4H, 3C), ZnS, ZnO, GaAs, Si
For example, a substrate material different from a conventionally known nitride semiconductor can be used.

Further, it is desirable to use a substrate that is off-angled (inclined) in a step-like manner as the heterogeneous substrate 1 different from the nitride semiconductor used in the present invention. When a sapphire substrate is used, the off-angle is perpendicular to the sapphire A plane (parallel to the M-axis direction of sapphire), and the off-angle is preferably in the range of 0.1 ° to 0.3 °. A nitride semiconductor device can be obtained.

When the off angle is in the range of 0.1 ° to 0.3 °, the surface morphology of the second nitride semiconductor and the third nitride semiconductor laminated by the HVPE method is parallel to the steps of the heterogeneous substrate. It becomes a streak. The steps (the direction along the step) on the surface of the nitride semiconductor are the same as the direction of the waveguide at the time of manufacturing the laser element, and there is no step-like step in the waveguide structure, which is the best. More preferably 0.15 °
It is good to be set to ~ 0.25 °.

When sapphire having an off angle smaller than 0.1 ° or not off-angle is used, the surface morphology of the second nitride semiconductor layer and the third nitride semiconductor layer becomes hexagonal pyramid (or hexagonal). (A shape similar to a weight), and the hexagonal pattern is also reflected on the surface of the nitride semiconductor formed thereon, which deteriorates the device characteristics. In addition, when sapphire having an off angle of more than 0.3 ° is used, the surface becomes rough, the deviation of the sapphire from the C plane increases, and epitaxial growth becomes difficult.

The first step of the lateral growth of the present invention may be repeated twice or more. By repeating this, the number of crystal defects in the nitride semiconductor layer formed thereon can be further reduced. When the lateral growth is repeated, the concave and convex portions formed on the convex portion and the convex portions on the concave portion are formed with respect to the irregularities in the lateral growth performed before that.

Next, as a second step, as shown in FIG. 2, a second nitride semiconductor 3 is grown on the epitaxially grown first nitride semiconductor layer 2 by using the HVPE method. It is desirable that the nitride semiconductor formed by the HVPE method is formed as a thick film and has a thickness of 400 μm or less including the underlayer. If the thickness is more than 400 μm, the warpage caused by lattice mismatch with a heterogeneous substrate or a difference in thermal expansion coefficient becomes too large, which causes inconvenience when laminating a nitride semiconductor as an element structure. This is caused by strain due to lattice mismatch or thermal expansion coefficient difference between the nitride semiconductor and the heterogeneous substrate, but initially due to lattice mismatch or thermal expansion coefficient difference because the heterogeneous substrate has a larger film thickness. The stress depends on the dissimilar substrate 1, and the nitride semiconductor is in a state of receiving a strain stress. However, when the nitride semiconductor is larger than 400 μm, since the stress gradually depends on the nitride semiconductor, the strain stress applied to the nitride semiconductor begins to be relaxed,
This time, the dissimilar substrate came to receive strain stress,
Then, a large warpage occurs.

Further, performing the second step has the following effects. When the first nitride semiconductor layer 2 is grown by lateral growth in the first step, the number of crystal defects on the surface of the first nitride semiconductor layer is non-uniform, but the second nitride semiconductor When layer 3 is grown,
Crystal defects are diffused in the second nitride semiconductor, become substantially uniform on the surface of the second nitride semiconductor layer, and the nitride semiconductor grown thereon can be grown as a uniform layer.

When growing the second nitride semiconductor layer 3, it is desirable to dope n-type impurities of Si or Sn. This is to improve the ohmic property with the n-electrode. When an element structure is formed on a GaN substrate in the order of an n-layer, an active layer, and a p-layer, a p-electrode is formed on the p-layer side.
When forming an n-electrode on the n-layer side opposite to the p-electrode, that is, on the GaN substrate, doping with Si or Sn improves the ohmic properties.

The n-type impurity of Si or Sn is 5 ×
It is desirable to dope in the range of 10 ¹⁶ / cm ^{3 to} 5 × 10 ²¹ / cm ³ . If it is less than 5 × 10 ¹⁶ / cm ³ , the ohmic properties will be poor and 5 × 10 ²¹ / cm 3
^{If it is} more than ³ , the crystallinity is deteriorated due to the high impurity concentration, and the crystal defects tend to increase. A preferable range is 1 × 10 ¹⁷ / cm ³ to 1 × 10 ²⁰ / cm ³ .

Next, as a third step, as shown in FIG. 3, after forming up to the second nitride semiconductor 3, polishing is performed from the exposed surface side of the heterogeneous substrate 1, and at least up to the heterogeneous substrate. Remove. When the epitaxially grown layer is formed using a mask material such as SiO _2, it is desirable that the layer to be removed by polishing be removed up to the mask material and the like. When the dissimilar substrate 1 is removed by polishing, the stress dependent on the dissimilar substrate becomes dependent on the nitride semiconductor, as described above. As a result, the dissimilar substrate 1 is completely removed. At this stage, a nitride semiconductor in a greatly warped state is obtained.

Using the nitride semiconductor having a large warp as a fourth step, a third nitride semiconductor 4 is grown by HVPE as shown in FIG. This HVPE
By forming the third nitride semiconductor 4 as a thick film by the method described above, a GaN substrate with reduced warpage can be obtained. This is a heterogeneous substrate 1
The second nitride semiconductor 3 which has been subjected to the strain stress due to lattice mismatch with the nitride semiconductor is further laminated with the nitride semiconductor in a state where the heterogeneous substrate has been removed, so that the strain stress is gradually removed, It is considered that the warpage was reduced.
This third nitride semiconductor is formed to have a thickness of 10 μm to 800 μm, preferably 200 μm to 500 μm.

Next, preferably, as a fifth step, as shown in FIG. 5, a part or all of the second nitride semiconductor 3 or the third Of the nitride semiconductor 4 is removed. This is because the first nitride semiconductor 2 obtains lateral growth.
Since a mask such as SiO ₂ is included or a nitride semiconductor is formed on top of forming irregularities, it is difficult to remove a strain stress. Therefore, the first nitride semiconductor layer and the second nitride semiconductor are formed. It is desirable to remove part or all of the semiconductor layer by polishing. By this polishing, the final film thickness as a GaN substrate is 50 μm to 500 μm,
Preferably, it is 100 μm to 300 μm.

The GaN substrate 4 'manufactured as described above
Is used, when an n-type nitride semiconductor, an active layer, and a p-type nitride semiconductor are formed on a GaN substrate to produce a nitride semiconductor device, the warpage is small and the number of defects is small.
A nitride semiconductor device with good yield and excellent luminous efficiency can be obtained.

[0034]

[Example 1] A sapphire substrate 1 having a 2-inch φ, C surface as a main surface and an orientation flat surface as an A surface was set in a MOVPE reaction vessel as a heterogeneous substrate 1, and the temperature was set at 5 ° C.
At 10 ° C., a buffer layer (not shown) made of GaN is grown to a thickness of about 200 Å on the sapphire substrate 1 using hydrogen as the carrier gas and ammonia and TMG (trimethylgallium) as the source gas. .

After growing the buffer layer, only TMG is stopped,
Increase temperature to 1050 ° C. When the temperature reaches 1050 ° C., a nitride semiconductor layer 2 made of GaN is further grown to a thickness of 2.5 μm using TMG.

After the nitride semiconductor layer 2 is grown, a stripe-shaped photomask is formed and patterned by a CVD apparatus so as to have a stripe width (the upper portion of the convex portion) of 2 μm and a stripe interval (the lower portion of the concave portion) of 10 μm. Done S
An iO ₂ film is formed, and then the first nitride semiconductor layer 2 in a portion where the SiO ₂ film is not formed is etched halfway by an RIE apparatus so that the first nitride semiconductor 2 remains, thereby removing irregularities. By forming, the first nitride semiconductor 2 is exposed on the side surface of the concave portion (2a in FIG. 1). After forming the irregularities as shown in FIG. 1, the SiO ₂ above the convex portions is removed. As shown in FIG. 6, the stripe direction is formed in a direction perpendicular to the orientation flat surface (M-axis direction of GaN).

Next, it is set in a MOVPE reaction vessel,
A nitride semiconductor layer 2b made of undoped GaN at a temperature of 1050 ° C. using TMG and ammonia as source gases
Is grown to a thickness of 15 μm, and this is used as the first nitride semiconductor layer 2.

After the growth of the first nitride semiconductor layer 2, the wafer is transferred to an HVPE apparatus at a temperature of 1050 ° C.
Using gallium chloride, ammonia, and silane gas as source gases, a second nitride semiconductor layer 3 made of GaN doped with 1 × 10 ¹⁸ / cm ^{3 of} Si is grown to a thickness of 250 μm.

At this time, when the number of crystal defects is observed by a cross-sectional TEM (transmission electron microscope), the crystal defect density on the surface of the first nitride semiconductor layer 2 is 10 ¹⁰ / cm on the convex portion and on the concave portion. Was less than 10 ⁴ pieces / cm ² ,
Is approximately uniform on the surface of the nitride semiconductor layer 3 of 10 ⁶ / cm ²
Became.

Subsequently, the wafer is taken out of the reaction vessel,
Polishing is performed from the sapphire substrate side until the sapphire substrate 1 is completely removed and the underlying layer GaN is exposed. When all the sapphire substrates have been removed, the wafer is largely warped.

Next, the wafer from which the sapphire substrate has been removed is transferred to the HVPE apparatus again, and
GaN doped with Si at 1 × 10 ¹⁸ / cm ³ using gallium chloride, ammonia, and silane gas as raw material gases
A third nitride semiconductor layer 4 of a thickness of 300 μm is grown. The growth of the third nitride semiconductor layer reduces warpage.

After the third nitride semiconductor layer 4 is grown, the wafer is taken out of the reaction vessel, and the first nitride semiconductor layer 2 and the second nitride semiconductor layer 3 are removed from the side of the sapphire substrate removed earlier. The GaN substrate 4 ′ having a total thickness of 250 μm is finally polished. G obtained
Since the aN substrate 4 'has a small warpage and few defects, a nitride semiconductor device formed on this GaN has a good yield and excellent luminous efficiency.

[Embodiment 2] In the same manner as in Embodiment 1, GaN
A substrate 4 'is manufactured. On the obtained GaN substrate, as shown in FIG. 7, a crack prevention layer made of InGaN (this can be omitted), an n-side cladding layer 6 made of a superlattice of AlGaN and Si-doped GaN, and GaN n
Side light guide layer 7, active layer 8 of multiple quantum well structure (MQW) made of InGaN, p-side cap layer 9 made of Mg-doped AlGaN, p-side light guide layer 10 made of Mg-doped GaN, AlGaN and Mg-doped P-side cladding layer 11 made of a superlattice with GaN, Mg-doped Ga
N-side p-side contact layers 12 are sequentially stacked.

After the lamination, the p-side contact layer 12 and the p-side cladding layer 11 are etched to form a ridge-shaped surface.
An insulating film 31 of ZrO ₂ or the like and a p-ohmic electrode 20 are formed on the ridge, and finally a p-pad electrode 21 and an n-ohmic electrode 22 and n
A pad electrode 23 is formed, and finally, a resonance surface is formed by cleaving GaN to form a chip. As described above, a nitride semiconductor laser device was obtained, this was mounted on a heat sink face up (in a state where the substrate and the heat sink were opposed to each other), and the respective electrodes were wire-bonded, and continuous oscillation was attempted at room temperature. However, the threshold current density is 2 kA / c.
At the output of the m ^2, 20 mW, continuous oscillation is confirmed,
It showed a life of 2000 hours or more.

[Embodiment 3] In the same manner as in Embodiment 2, on the GaN substrate obtained in Embodiment 1, as shown in FIG. 8, an n-side contact layer 5 made of AlGaN as an element structure, a crack prevention layer (omitted) Possible), n-side cladding layer 6,
An n-side light guide layer 7, an active layer 8, a p-side cap layer 9, a p-side light guide layer 10, a p-side cladding layer 11, and a p-side contact layer 12 are laminated.

Next, a part of the p-side contact layer 12 is etched to expose the n-side contact layer 5. Further, the p-side layer is dry-etched by RIE to the p-side cladding layer 11 to form a ridge, and Zr is formed on the ridge as a protective film.
An insulating film 31 such as O ₂ and p on each contact layer
An ohmic electrode 20 and a p-pad electrode 21 and an n-ohm electrode 22 and an n-pad electrode 23 are formed. Finally, a resonance surface is formed by cleaving GaN to form a chip.

As described above, a nitride semiconductor laser device is obtained, and the nitride semiconductor laser device is mounted on a heat sink face up (in a state where the substrate and the heat sink are opposed to each other). In the experiment, continuous oscillation was confirmed at a threshold current density of ² kA / cm ² and an output of 20 mW, indicating a life of 1000 hours or more.

Example 4 A sapphire substrate 1 having a 2 inch φ, C surface as a main surface and an orientation flat surface as an A surface was set in a MOVPE reaction vessel as a heterogeneous substrate 1, and the temperature was set at 5 ° C.
At 10 ° C., a buffer layer (not shown) made of GaN is grown to a thickness of about 200 Å on the sapphire substrate 1 using hydrogen as the carrier gas and ammonia and TMG (trimethylgallium) as the source gas. .

After growing the buffer layer, only TMG is stopped,
Increase temperature to 1050 ° C. When the temperature reaches 1050 ° C., a nitride semiconductor layer 2 a made of GaN is further grown to a thickness of 2.5 μm using TMG.

After growing the nitride semiconductor layer 2a, a stripe-shaped photomask is formed, and a protective film 3 made of SiO _{2 having a} stripe width of 10 μm and a window of 2 μm is formed by a CVD apparatus.
0 is formed with a thickness of 0.5 μm. The stripe direction is
It is formed in a direction perpendicular to the orientation flat surface.

After the formation of the protective film 30, the wafer is subjected to MOVPE.
Transfer to a reaction vessel, and at 1050 ° C, TMG,
Using ammonia, a nitride semiconductor layer 2b made of undoped GaN was grown to a thickness of 15 μm,
Of the nitride semiconductor layer 2.

After growing the first nitride semiconductor layer 2, the wafer is transferred to an HVPE apparatus at a temperature of 1050 ° C.
Using gallium chloride, ammonia, and silane gas as source gases, a second nitride semiconductor layer 3 made of GaN doped with 1 × 10 ¹⁸ / cm ^{3 of} Si is grown to a thickness of 250 μm (FIG. 6).

At this time, when the number of crystal defects is observed by a cross-sectional TEM (transmission electron microscope), the crystal defect density on the surface of the first nitride semiconductor layer is 10 ⁴ / cm ² on the convex portion, and is on the concave portion. Was less than 10 ¹⁰ / cm ² , but was almost uniform on the second nitride semiconductor layer to 10 ⁶ / cm ² .

Subsequently, the wafer is taken out of the reaction vessel,
The sapphire substrate side is polished to a part of the first nitride semiconductor layer ₂ to completely remove the sapphire substrate and SiO ₂ of the protective film. This sapphire and Si
When all O ₂ has been removed, the wafer is largely warped.

Next, the wafer from which the sapphire substrate 1 has been removed is transferred to the HVPE apparatus again, and
At 0 ° C., gallium chloride TMG, ammonia,
Using a silane gas, a third nitride semiconductor layer made of GaN doped with 1 × 10 ¹⁸ / cm ^{3 of} Si is grown to a thickness of 300 μm. By growing the third nitride semiconductor layer 4, warpage is reduced.

After the third nitride semiconductor layer 4 has been grown, the wafer is taken out of the reaction vessel, and the remaining first nitride semiconductor layer 2 and second nitride semiconductor layer 3 are placed from the sapphire substrate side removed earlier. Is finally polished to form a GaN substrate 4 'having a total thickness of 250 μm. Since the obtained GaN substrate 4 ′ has a small warpage and few defects, the nitride semiconductor device formed on GaN
Good yield and good luminous efficiency were obtained.

[Example 5] A GaN substrate 4 'was obtained in the same manner as in Example 1, except that the third nitride semiconductor 4 was changed to undoped GaN. As shown in FIG. 7, a crack prevention layer made of InGaN (this can be omitted), an n-side cladding layer 6 made of a superlattice of AlGaN and Si-doped GaN,
N-side light guide layer 7 made of InGaN, active layer 8 having a multiple quantum well structure (MQW) made of InGaN, Mg-doped AlG
p-side cap layer 9 made of aN, p-side optical guide layer 10 made of Mg-doped GaN, p-side cladding layer 11 made of a superlattice of AlGaN and Mg-doped GaN, p-side contact layer made of Mg-doped GaN 12 are sequentially stacked.

After the lamination, the p-side contact layer and the p-side cladding layer are etched to form a ridge surface, an insulating film 31 such as ZrO ₂ and a p-ohmic electrode 20 are formed on the ridge, and finally a p-pad electrode is formed. An n-ohmic electrode 22 and an n-pad electrode 23 are formed on the GaN substrate side opposite to the p-electrode, and finally a resonance surface is formed by cleavage of GaN to form a chip. As described above, a nitride semiconductor laser device was obtained, this was mounted on a heat sink face up (in a state where the substrate and the heat sink were opposed to each other), and the respective electrodes were wire-bonded, and continuous oscillation was attempted at room temperature. However, the threshold current density is ² kA / cm ² , 2
At an output of 0 mW, continuous oscillation was confirmed.
It showed a lifetime of more than hours.

[Embodiment 6] In the sapphire substrate 1 having a 2-inch φ, C-plane as a main surface and an orientation flat surface as an A-plane as the heterogeneous substrate 1, the sapphire substrate 1 is further off-angled on a step, and the off-angle is set to 0. A nitride semiconductor laser device was obtained in the same manner as in Example 2 except that a substrate formed at 13 ° and the direction along the step (step direction) was perpendicular to the A-plane, and continuous oscillation was attempted at room temperature. Threshold current density 2 kA / c
At the output of the m ^2, 20 mW, continuous oscillation is confirmed,
It showed a life of more than 3000 hours.

[Embodiment 7] In the same manner as in Embodiment 1, GaN
A substrate 4 'is manufactured. AlGa on the obtained GaN substrate
N-side contact layer 5 made of N, a crack prevention layer made of InGaN (this can be omitted), AlGaN
N-side cladding layer 6 made of superlattice of Si and GaN doped with Si, multiple quantum well structure (MQW) made of InGaN
Active layer 8, a p-side cap layer 9 made of Mg-doped AlGaN, a p-side cladding layer 11 made of a superlattice of AlGaN and Mg-doped GaN, and a p-side contact layer 12 made of Mg-doped GaN are stacked in this order. . After lamination, p
P ohmic electrode (transparent electrode) on the side contact layer 12
20 and a p-pad electrode 21 are formed.
The n ohmic electrode 22 and the n pad electrode 2
3 is formed, and finally a chip is formed by cleavage of GaN.
The LED element obtained as described above has a forward current of 20
At mA, the device exhibited blue light emission with a forward voltage of 3.4 V and 465 nm, and the light emission output was 9 mW.

[0061]

As described above, according to the conventional method of obtaining a GaN substrate, stress is generated due to lattice mismatch between the heterogeneous substrate and GaN, and the substrate is greatly warped. However, according to the method of the present invention, However, if GaN is polished from the heterogeneous substrate side and only GaN is used, warpage occurs. However, when GaN is further laminated on this GaN substrate with a thick film, distortion caused by lattice mismatch between the heterogeneous substrate and GaN is caused. Stress is relieved, warpage is reduced, and a good GaN substrate is obtained.

Further, since the GaN substrate obtained by the manufacturing method of the present invention is manufactured using GaN grown epitaxially, a GaN substrate having very few crystal defects can be obtained as a relatively thick film. It is useful for manufacturing a complex nitride semiconductor laser device.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a structure of a GaN substrate for explaining a first step of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a structure of a GaN substrate illustrating a second step of the present invention.

FIG. 3 is a schematic cross-sectional view showing a structure of a GaN substrate for explaining a third step of the present invention.

FIG. 4 is a schematic cross-sectional view illustrating a structure of a GaN substrate illustrating a fourth step of the present invention.

FIG. 5 is a schematic cross-sectional view showing a structure of a GaN substrate for explaining a fifth step of the present invention.

FIG. 6 is a schematic sectional view showing the structure of a laser device using a GaN substrate for explaining another embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view showing the structure of a laser device using a GaN substrate obtained according to an embodiment of the present invention.

FIG. 8 shows GaN obtained according to another embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view showing the structure of a laser device using a substrate.

FIG. 9 shows GaN obtained according to another embodiment of the present invention.
FIG. 3 is a schematic cross-sectional view showing the structure of a laser device using a substrate.

[Brief description of reference numerals]

DESCRIPTION OF SYMBOLS 1 ... Different substrate 2 ... 1st nitride semiconductor layer 3 ... 2nd nitride semiconductor layer 4 ... 3rd nitride semiconductor layer 4 '... GaN substrate 5 ... n-side contact layer 6 ... n-side cladding layer 7 ... n-side light guide layer 8 ... active layer 9 ... p-side cap layer 10 ... p-side light guide layer 11 ... p-side Cladding layer 12 ... p-side contact layer 20 ... p ohmic electrode 21 ... p pad electrode 22 ... n ohmic electrode 23 ... n pad electrode 30 ... SiO ₂ 31 ... insulating film

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 AA11 AA13 AA17 BA08 BA38 BB01 BB12 CA05 DA08 HA01 JA01 LA14 5F041 AA31 AA40 CA05 CA34 CA40 CA46 CA57 CA64 CA65 CA74 CA77 CB04 5F045 AA04 AA07 AB14 AB40 AC01 AD03 AC08 AF12 AF04 AF06 AF09 AF13 BB12 CA11 CA12 CB02 DA52 DA53 DA54 DB02 HA12 5F052 KA01 5F073 AA13 AA45 CA07 CB05 CB19 DA05 DA35 EA29

Claims (9)

[Claims] 1. A method of manufacturing a GaN substrate which is a nitride semiconductor device by laminating a nitride semiconductor on a GaN substrate, wherein the first nitride including GaN by lateral growth on a heterogeneous substrate different from the nitride semiconductor A first step of growing a nitride semiconductor layer, a second step of growing a second nitride semiconductor thereon, and a third step of removing at least up to a heterogeneous substrate after the second step.
And a fourth step of, after the third step, growing a third nitride semiconductor on the second nitride semiconductor. 2. The first step comprises, after growing GaN on a heterogeneous substrate, forming irregularities on the surface of the GaN, and growing the GaN in a substantially horizontal direction at least from the surface of the concave portion to the surface of the convex portion. The method for manufacturing a GaN substrate according to claim 1, wherein 3. A fifth step of removing part or all of the second nitride semiconductor or part of the third nitride semiconductor from the side from which the heterogeneous substrate has been removed after the fourth step. The method for manufacturing a GaN substrate according to claim 1, wherein the GaN substrate is provided. 4. The thickness of the second nitride semiconductor layer is 10
The method for producing a GaN substrate according to claim 1, wherein the thickness is adjusted to be not less than μm and not more than 400 μm. 5. The semiconductor device according to claim 1, wherein said third nitride semiconductor layer has a thickness of 10
The method for producing a GaN substrate according to any one of claims 1 to 4, wherein the thickness is adjusted to 0 µm or more and 400 µm or less. 6. The method according to claim 1, wherein the first step is to grow the nitride semiconductor by MOVPE, and the second and fourth steps are to grow the nitride semiconductor by HVPE. Item 13. The method for producing a GaN substrate according to item 1. 7. The method according to claim 3, wherein after the fifth step, the GaN substrate is polished to a thickness of 100 μm or more and 300 μm or less, and a device structure is formed thereon. 2. The method for producing a GaN substrate according to claim 1. 8. A different substrate different from the nitride semiconductor,
The method of manufacturing a GaN substrate according to any one of claims 1 to 7, wherein a sapphire substrate that is off-angled with respect to a plane is used. 9. The semiconductor device according to claim 1, wherein the second nitride semiconductor layer and / or the third nitride semiconductor layer is doped with Si or Sn.
Item 13. The method for producing a GaN substrate according to item 1.