JP3263891B2 - Gallium nitride based semiconductor crystal growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to gallium nitride (Ga) nitride.
The present invention relates to a method for growing an N) -based semiconductor crystal, and more particularly, to a method for epitaxially growing a GaN-based semiconductor crystal having excellent crystallinity, which is suitable as a blue light emitting material. In the present specification, the GaN-based crystal, GaN, AlN (aluminum nitride), InN is (indium nitride), and their mixed crystal _{In x Ga y Al 1-xy} N (0 ≦ x, 0 ≦ y, x
+ Y ≦ 1).

[0002]

2. Description of the Related Art Recently, GaN-based semiconductors have attracted attention as blue light-emitting materials. Conventionally, when epitaxially growing a GaN-based semiconductor crystal, sapphire (α-Al ₂ O
₃ ) The (0001) plane of the GaN-based semiconductor crystal is often aligned with the (0001) plane of the sapphire substrate using a substrate. At this time, the deviation of the lattice constant is as large as 16%, and there is a problem that a GaN-based semiconductor crystal having excellent crystallinity cannot be grown.

As a solution, a method of growing an AlN film serving as a buffer layer on a sapphire substrate, and growing a GaN-based semiconductor crystal on the AlN film (Japanese Patent Publication No. Sho 59-4)
8794, JP-A-2-229476), GaAl
A method of growing a GaN-based semiconductor crystal on a buffer layer made of N (Japanese Patent Application Laid-Open No. H4-297023) has been proposed. According to these proposals, the introduction of the buffer layer alleviates the lattice mismatch between the sapphire substrate and the GaN-based semiconductor crystal, and improves the surface morphology and crystallinity of the GaN-based semiconductor crystal.

As another solution, aluminum garnet (ReAl ₂ Al ₃ O ₁₂ , where Re is Gd,
Dy, Ho, Er, Tm, Yb, Lu, or Y. ) Or gallium garnet (ReAl ₂ G)
a ₃ O ₁₂ , where Re is Pr, Nd, Sm, Eu, G
d, Er, Tm, Yb, Lu, or Y. ) (Japanese Patent Application Laid-Open No. 49-389)
No. 9) and a method using a substrate made of MnO, ZnO, MgO, CaO or the like (JP-A-4-209577). According to these proposals, the mismatch in lattice constant is greatly reduced as compared with the case where sapphire is used as a substrate, and a good substrate surface can be easily obtained, and a GaN crystal with good crystallinity can be obtained. I have.

[0005]

However, the above A
In the proposal of providing the 1N buffer layer and the GaAlN buffer layer, since the lattice mismatch between the GaN-based semiconductor crystal and the sapphire substrate is not eliminated, the Ga
The N-based semiconductor crystal is still in a considerably distorted state. Therefore, even if a light emitting element is manufactured using such a distorted crystal layer, there is a problem that the luminance is not improved as expected.

In the above proposal using aluminum garnet or gallium garnet as a substrate, since the lattice constant of the substrate is in the range of 12.00 to 12.57 angstroms, the lattice spacing of the (111) plane of the crystal is This corresponds to five times the a-axis of GaN, and lattice matching is not always good. Therefore, there is a problem that the distortion of the GaN-based semiconductor crystal is not eliminated, and the luminance of the manufactured light emitting element is not improved.

Furthermore, MnO, ZnO, MgO or C
In the proposal using a substrate such as aO, instead of improving lattice matching, the growth temperature of the GaN-based semiconductor crystal (approximately 100
0 ° C.), the substrate is thermally decomposed and Ga
There is a problem that an N-based semiconductor crystal layer cannot be obtained.

Therefore, the present applicant has previously proposed a substrate material having good lattice matching with a GaN-based semiconductor crystal and being stable even at the growth temperature of the GaN-based semiconductor crystal.
Rare earth group 3B perovskite such as neodymium gallate (NdGaO ₃ ) is suitable, and it has been proposed to use the {101} plane or the {011} plane of the crystal (Japanese Patent Application No. 6-131).
-246803). However, subsequent studies have shown that the rare-earth group 3B perovskite crystal system (rhombic) and GaN
Is different from the crystal system (hexagonal) of
When a GaN-based semiconductor crystal is grown on a group III perovskite substrate, a desired crystal plane of the GaN-based semiconductor crystal (0
It has been found that a crystal plane different from the c-plane may grow without growing the (001) plane (c-plane).

The present invention has been made in view of the above circumstances, and uses a rare earth 3B group perovskite as a substrate and stably grows a c-plane of a GaN-based semiconductor crystal on a {101} plane or a {011} plane of the substrate. It is an object of the present invention to provide a crystal growth method improved so that it can be performed, thereby obtaining a high-quality GaN-based semiconductor crystal suitable as a blue light emitting material.

[0010]

Means for Solving the Problems In order to achieve the above object, the present inventor has proposed that the surface of a rare earth group 3B perovskite substrate be treated by an appropriate method before the start of the growth of a GaN-based semiconductor crystal, so that the surface of the substrate is treated with an appropriate method. To the GaN-based semiconductor crystal c
The inventor thought that the surface could be grown stably and made intensive studies, and as a result, completed the present invention.

That is, according to the present invention, when a GaN-based semiconductor crystal is grown on a substrate, rare-earth 3B
Using a {101} plane or {011} plane of a group III perovskite, exposing the substrate to an atmosphere composed of a compound containing a group 3B element, and then starting the growth of a GaN-based semiconductor crystal. I do. Here, {101}
The plane or {011} plane represents a plane equivalent to the (101) plane or the (011) plane, respectively, and includes the (1 to 01) plane,
(101 ~) plane, (1 ~ 01 ~) plane, or (01 ~) plane
1) plane, (011 ~) plane, (01 ~ 1 ~) plane. Note that an index with "~" appended to the right shoulder is a negative index. Alternatively, a substrate slightly off-angled from the {101} plane or the {011} plane may be used.

Specifically, for example, the compound containing a Group 3B element is a chloride of a Group 3B element such as gallium chloride, and the substrate is made of neodymium gallate represented by NdGaO ₃ . The compound containing a Group 3B element is not limited to a chloride of a Group 3B element such as gallium chloride, and the substrate may be a rare-earth Group 3B perovskite other than NdGaO ₃ . Here, the rare earth element does not need to be a single element, but may be a mixture with a group 3B element of the periodic table. Group 3B elements are Al, Ga, In and mixtures thereof.

[0013]

According to the above means, the rare earth 3B is used as the substrate.
By using a {101} plane or {011} plane of group III perovskite, and exposing the substrate to an atmosphere consisting of a compound containing a group 3B element such as gallium before starting the growth of a GaN-based semiconductor crystal. Then, gallium or the like is adsorbed or deposited on the substrate surface while being oriented in the c-axis direction. Thereby, it is considered that the orientation of the GaN-based semiconductor crystal grown thereafter is determined in the c-axis direction, and the (0001) plane of the GaN-based semiconductor crystal is placed on the {101} plane or the {011} plane of the rare earth 3B group perovskite substrate. (C-plane) grows. In addition, a rare earth 3B group perovskite substrate of $ 10
C of GaN-based semiconductor crystal on 1} plane or {011} plane
As the plane grows, the lattice mismatch between the substrate and the GaN-based crystal is minimized.

Here, the advantage of using the {101} plane or the {011} plane of the rare earth group 3B perovskite as a substrate will be described. In general, the rare earth group 3B perovskite has a high melting point, is thermally stable at a temperature at which a GaN-based semiconductor crystal is grown, and has a raw material gas of H.
It is chemically stable to Cl (hydrogen chloride), NH ₃ (ammonia) and the like. Further, as described below,
The lattice matching with the aN-based semiconductor crystal is also good.

FIG. 1 shows the (011) plane or (101) plane 3B of a rare earth 3B group perovskite crystal which is orthorhombic.
1 shows an arrangement of group atoms. The lattice spacing indicated by the dotted line in FIG. 1 is equal to the length of the a-axis in the (011) plane, and equal to the length of the b-axis in the (101) plane. The lattice spacing indicated by the solid line is the same as the (011) plane and ( 101) Both surfaces have the square root of the sum of the squares of the lengths la, lb, and lc of the a-axis, b-axis, and c-axis, respectively.
It is equal to one part. In the rare earth group 3B perovskite, la and lb are substantially equal between the above axes, and the following equation: lc = √ (la ² + lb ² ) / 2 is substantially established. On the (011) plane or the (101) plane, they are arranged in a substantially hexagonal lattice state as shown in FIG.

FIG. 2 shows the arrangement of Ga atoms on the (0001) plane of GaN. The lattice spacing indicated by the dotted line in FIG.
It is √3 times the length of the axis, and the lattice spacing indicated by the solid line is equal to the length of the a-axis.

FIG. 3 shows the atomic arrangement of the (011) plane or (101) plane of the rare earth gallium perovskite crystal when Nd (neodymium) is selected as the rare earth element,
FIG. 4 shows a diagram in which the atomic arrangement of the (0001) plane of N is associated. The white circles in the figure indicate the atomic arrangement of the (011) plane or the (101) plane of the rare earth gallium perovskite crystal, and the black circles indicate the atomic arrangement of the (0001) plane of GaN. From FIG. 3, √3 times the length of the a-axis of GaN is ２ of the square root of the sum of the squares of the respective lengths of the a-axis, b-axis, and c-axis of the rare earth gallium perovskite crystal, and the length of the a-axis. Or b
If the value is substantially equal to any of the lengths of the axes, it can be understood that lattice matching is performed. By the way, in the case of rare earth gallium perovskite crystal, the deviation of the lattice spacing from GaN is 0.1 to
It is in the range of 6.1%, considerably smaller than 16% for sapphire. In particular, LaGaO ₃ , PrGaO ₃
And in the case of NdGaO ₃ , the deviation of the lattice spacing is 0.1
-1.8%. In the case of a rare earth aluminum perovskite crystal, the lattice spacing shift is 3.6 to 8.3.
% Range. In the case of a rare earth indium perovskite crystal, the lattice gap between GaN and GaN is large.
In the case of nGaO ₃ , lattice matching is almost achieved with In _0.4 Ga _0.6 N, which is advantageous when a mixed crystal of InN and GaN is grown.

In the (011) plane or the (101) plane of the rare earth group 3B perovskite crystal, the substrate outermost surface layer is a group 3B element, so that the GaN-based compound semiconductor crystal containing the same kind of element has the same kind of element. It is considered that the growth is easier than when a substrate such as sapphire, which does not contain sapphire is used.

[0019]

EXAMPLES The features of the present invention will be clarified below with reference to examples and comparative examples. The following embodiments are merely examples of the present invention, and it goes without saying that the present invention is not limited by the embodiments.

(Example) A thickness of 500 μm and a plane orientation (01
After washing the substrate made of NdGaO _{3 in} 1) with an organic solvent, the substrate was placed in a hydride VPE device. Then, the substrate portion was maintained at 800 ° C., the Ga raw material portion was maintained at 850 ° C., and N ₂ (nitrogen gas) was flowed as a carrier gas. Subsequently, HCl gas diluted with N ₂ was flowed from the upstream side of the Ga raw material, and GaCl, a reaction product of the Ga raw material and HCl, was transported to the substrate portion. Although not particularly limited,
For example, in this example, the GaCl treatment was performed for 5 minutes.
Thereafter, in parallel with the above gas, an NH ₃ gas was flowed immediately before the substrate, bypassing the Ga raw material portion, and the NH ₃ gas was reacted with GaCl to epitaxially grow GaN on the substrate. Although not particularly limited, for example, this GaN
Was epitaxially grown for 30 minutes. The film thickness of GaN obtained in this example was about 2 μm, and no abnormal growth was observed on the surface. Also, this GaN
The X-ray diffraction pattern of the film is shown in FIG. 4. As is clear from FIG. 4, since the diffraction of (0002) and (0004) is strong, the main surface of the grown GaN is the (0001) plane (c
Face).

(Comparative Example) GaN was directly epitaxially grown on a NdGaO ₃ substrate having a plane orientation of (011) under the same conditions and in the same procedure as in the above example, except that the GaCl treatment for 5 minutes was not performed. FIG. 5 shows the X-ray diffraction pattern of the GaN film obtained in the comparative example. As is clear from FIG. 5, the main surface of the grown GaN is the (112-4) plane, and the diffraction from the c-plane is Not at all.

As described above with reference to a specific example, by applying the present invention to a NdGaO ₃ substrate and subjecting the NdGaO ₃ substrate to GaCl treatment before starting the epitaxial growth of GaN, the (0001) plane of the GaN crystal is formed on the substrate. It was confirmed that (c-plane) grew stably.

In the above embodiment, the substrate material is NdGaO ₃ , but other rare earth 3B group perovskites, such as rare earth aluminum perovskite, can stably grow the c-plane of the GaN crystal on the substrate. The same effect can be obtained. The plane orientation of the substrate is (011), which is equivalent to (011).
1), (011), (01-1), or (101) and its equivalent (1-01),
(101 ~), (1 ~ 01 ~)
Furthermore, even if the plane is slightly off-angle from each plane orientation, the same effect that the c-plane of the GaN crystal grows stably can be obtained.

In the above embodiment, the surface of the substrate was processed by transporting GaCl to the substrate before the start of the epitaxial growth of GaN. However, the gas flowing through the substrate during the processing is not limited to GaCl. Any gas of a compound containing a Group 3B element may be used.

Furthermore, in the above embodiment, the GaN crystal is epitaxially grown on the substrate is not limited thereto, AlN, is a mixed crystal of InN and GaN and their _{In x Ga y Al 1-xy} N ( 0 ≦ x, 0 ≦ y, x + y ≦
Even when 1) is grown, a similar effect that the c-plane of the crystal grows stably can be obtained.

Further, the present invention relates to a hydride VP
The present invention is not limited to the case where the GaN-based semiconductor crystal is epitaxially grown by the E method, but can be applied to other growth methods such as the MOCVD (metal organic chemical vapor deposition) method.

[0027]

According to the gallium nitride based semiconductor crystal growth method of the present invention, when growing a gallium nitride based semiconductor crystal on a substrate, the {101} plane or {011} of a rare earth group 3B perovskite is used as the substrate. The substrate is exposed to an atmosphere made of a compound containing a Group 3B element in advance, and the growth of the gallium nitride-based semiconductor crystal is started. Therefore, the lattice matching with the GaN-based semiconductor crystal is relatively good. And a (000) GaN-based semiconductor crystal on a {101} plane or a {011} plane of a thermally and chemically stable rare earth 3B group perovskite substrate.
1) The plane (c-plane) grows stably. Therefore, a good GaN-based semiconductor crystal can be obtained as a blue light emitting semiconductor material.

[Brief description of the drawings]

FIG. 1 is a diagram showing an arrangement of Ga atoms on a (011) plane or a (101) plane of a rare earth gallium perovskite.

FIG. 2 is a diagram showing an arrangement of Ga atoms on a (0001) plane of GaN.

FIG. 3 shows the atomic arrangement of the (011) plane or (101) plane of rare earth gallium perovskite, and the (000) of GaN.
FIG. 1 is a diagram showing correspondence with a surface atomic arrangement.

FIG. 4 is a diagram showing an X-ray diffraction pattern of a GaN crystal grown in an example.

FIG. 5 shows, as a comparison, Ga grown without applying the present invention.
FIG. 3 is a view showing an X-ray diffraction pattern of an N crystal.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/205 C30B 25/18 C30B 29/40 502 H01L 33/00

Claims (3)

(57) [Claims] In growing a gallium nitride based semiconductor crystal on a substrate, a {101} plane or a {011} plane of a rare earth 3B group perovskite is used as the substrate, and the substrate is prepared from a compound containing a group 3B element in advance. A method for growing a gallium nitride-based semiconductor crystal, comprising: starting growth of a gallium nitride-based semiconductor crystal after exposure to an atmosphere. 2. The method of growing a gallium nitride-based semiconductor crystal according to claim 1, wherein the compound containing a Group 3B element is a chloride of a Group 3B element. 3. The method of growing a gallium nitride-based semiconductor crystal according to claim 2, wherein the substrate is made of neodymium gallate represented by NdGaO ₃ , and the chloride of the group 3B element is gallium chloride.