JPH11189498A - Production of nitride crystal, mixture, liquid phase growth, nitride crystal, nitride crystal powder, and vapor growth - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new method for crystal growth, enabling high-purity group III nitride crystal such as of GaN to be produced easily at low cost, in view of having been difficult to obtain large-sized crystal of such nitrides so far. SOLUTION: This new method comprises the following processes: a group III metallic element is heated and melted, the resulting melt 3 is then injected with a nitrogen atom-contg. gas such as NH3 at a temperature not higher than the melting point of the aimed nitride to produce group III nitride crystallites with high wettability to the melt 3; the resultant mixture of the above crystallites and the melt is used as starting material for the liquid growth process, or group III nitride powder afforded by eliminating the group III metallic element from the above mixture is used as starting material for the vapor growth process; alternatively, a seed crystal or substrate crystal is immersed in a group III element melt such as of Ga, bubbles of a nitrogen- contg. gas such as NH3 are intermittently contacted with the surface of the above crystal to react the gas with the group III element on the surface to effect the growth of the aimed group III nitride crystal on the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a nitride crystal of a group III element, especially a nitride crystal such as GaN, AlN, InN, etc., a mixture, a liquid phase growth method, a nitride crystal, a nitride crystal powder, And a vapor phase growth method.

[0002]

2. Description of the Related Art GaN, AlN, InN
There is no method that can easily produce large Group III nitride crystals such as those described above. If a GaN bulk crystal is made, the impact on the realization of a blue laser diode and the like is immeasurable. In addition, bulk crystals of wide-cap semiconductor materials are expected to become full-scale in the 21st century.

As a method for producing GaN crystal powder, a method has been put into practical use in which a Ga oxide such as Ga ₂ O ₃ is reacted with ammonia to produce the powder. Commercially available.

[0004] A method capable of easily producing a bulk crystal of a group III nitride crystal has not yet been developed. Slightly, the following document was published by S. Porowski et al., Which requires very high pressure, so that the size of the obtained crystal is several mm, while the production of the crystal is dangerous and difficult.
About small.

[0005] "Prospects for high-pressure crystal"
growth of III-V nitrides ”S.porowski, J.Jun, P.Perli
n, I.Grzegory, H.Teisseyre and T.SuskiInst.Phys.Con
f.Ser.No.137: Chapter 4Paper presented at the 5th
SiC and Related Materials Conf., Washington, DC, l99
Group III nitrides represented by 3GaN have a very high melting point, and sublimation and decomposition occur at a temperature lower than the melting point. Therefore, a melt cannot be formed, and crystal growth from the melt cannot be performed. Further, since the solubility in the group III melt is very low, crystal growth from the solution is also difficult. The group III nitride crystal growth methods that have been put into practical use so far include HVPE (hydride vapor phase epitaxy) and MOVPE (metal organic vapor phase epitaxy).
And MBE (molecular beam epitaxy). In addition, GaN-based LEDs manufactured by this method have been commercialized. MO
As examples of the crystal growth of GaN by the VPE method, the following documents have been published.

"Novel metalorganic chemical vapor de
position system for GaN growth ”S.Nakamura, Y.Hara
da and M. Seno, Appl.Phys.Lett.58 (18) 6, l991

[0007]

SUMMARY OF THE INVENTION GaN represented by II
In recent years, nitride crystals of Group I elements have attracted attention as materials for blue light-emitting devices. In order to produce an element, it is necessary to epitaxially grow, for example, a GaN crystal or the like on a substrate. In this epitaxial growth, it is implicit that the lattice constant and the coefficient of thermal expansion of the crystal serving as the substrate are the same as those of the crystal grown thereon in order to prevent the occurrence of strain in the crystal to be grown. However, a bulk crystal of nitride that can be used as a substrate has not been obtained so far, and a sapphire substrate or the like having a different lattice constant has been substituted and epitaxial growth has been performed thereon.

As the epitaxial growth method, MO
The VPE method is the mainstream, but the raw material, organometallic,
It is easy to catch fire and is dangerous and expensive. In addition, the need for large, complex and expensive growth equipment. It is inevitable that hydrogen is introduced as an impurity into the grown crystal, which causes a problem that it is difficult to increase the carrier of the p-type crystal.

Therefore, in order to increase the carrier of the p-type crystal, it is necessary to bring the p-type dielectric layer to the element surface and perform a nitride crystal treatment. Since it is necessary to bring the p-type dielectric layer to the element surface, the degree of freedom in designing the element structure is narrow.

As another epitaxial growth method, a group III nitride crystal is dissolved as a solute in a group III element solvent, and L
There is a method of PE (liquid phase epitaxial) growth. However, conventionally commercially available Group III nitride crystals are, for example, GaN, a fine powder produced by reacting a Ga oxide such as Ga ₂ O ₃ with ammonia. There is a problem that the surface of is difficult to get wet with Ga and therefore difficult to dissolve in Ga.

The powder of the nitride crystal may be used as a fluorescent material,
It is also expected to be applied as a dopant material in liquid phase epitaxial growth of GaAs, GaP and the like. However, conventionally commercially available GaN crystal powders are expensive, but have low purity, and are not suitable as starting materials for vapor phase growth. In addition, since it is difficult to melt into a semiconductor melt due to its shape,
There is a problem that it is difficult to use it as a raw material for liquid phase growth or as a dopant raw material.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a novel nitride crystal capable of easily and inexpensively obtaining a high-purity Group III element nitride crystal such as GaN. Manufacturing method, mixture, vapor phase growth method, nitride crystal,
It is to propose a nitride crystal powder and a vapor phase growth method.

Another object of the present invention is to provide a novel crystal growth method capable of easily growing a bulk crystal of a nitride crystal of a group III element such as GaN, which has not been obtained, and a simple and easy method. It is another object of the present invention to propose a novel crystal growth method capable of safely performing a group III nitride crystal epitaxial growth.

[0014]

The first gist of the present invention is as follows.
There are three main types.

A reaction is performed by injecting a nitrogen-containing gas such as ammonia into a high-temperature melt of a group III element such as Ga. As a result, a large amount of group III nitride microcrystals float in the melt of the group III element.

Using the mixture of the group III element and the group III nitride microcrystal thus obtained as a raw material, liquid phase epitaxial growth of the group III nitride crystal is performed. The group III element nitride microcrystals obtained by the above-mentioned method have good compatibility with the group III element melt, and the group III nitride microcrystals can be easily dissolved in the group III element melt.

A group III nitride crystal obtained by removing a group III element from the above mixture by acid washing or the like is used as a raw material to produce a group III nitride crystal in vapor phase growth, melting, and sintering. The raw material obtained by this method is characterized by high purity and low cost.

In detail, a method of synthesizing a group III-V compound by injecting a vapor of a group V element into a group III melt is called an injection method and is a known technique. For example, one of the III-V compound semiconductors, In,
As an example of synthesizing a polycrystalline P, there is also the following academic report.

"Mass synthesis of InP polycrystal by P-injection method", Shibata et al., The 34th Lecture Meeting on Applied Physics (1987) 28
pZ-1 However, the injection method produces a group III melt III −
A so-called melt growth method in which a group V compound is heated to a temperature equal to or higher than the melting point of the group V compound, a vapor of a group V element is injected therein, a melt of the group III-V compound is once formed, and the melt is cooled to form a crystal. In contrast, in the method for synthesizing a nitride according to claim 1 of the present invention, a gas containing nitrogen is injected into a group III melt at a temperature much lower than the melting point of the nitride to be synthesized. Liquid phase
A conventional injection method in which a group III element is reacted with a group V element in the gas phase to directly form a solid group III nitride crystal in the group III element melt (it is not possible to melt the nitride). This is a completely new synthesis method. This is the nitride II
It takes advantage of its very low solubility in Group I element melts, and actively utilizes it.

In the method for producing a nitride crystal according to claim 1, by mixing an impurity element with a group III metal element, a group III nitride crystal doped with impurities can be produced. 2). And this claim 1
Alternatively, a mixture of a group III nitride powder and a group III metal raw material can be obtained by the method for producing a nitride crystal described in (2).

The mixture of the group III nitride crystal and the group III metal raw material according to claim 4 of the present invention has a surface completely formed of the group III metal raw material even though the group III nitride crystal is microcrystal. There is a big feature in the wet point. When a crystal fine powder is added to a raw material for liquid phase growth or a dopant, a powder having a large surface area compared to its volume has a problem that it is hardly compatible with the Group III melt and is therefore very difficult to dissolve. In particular, in nitride crystals having low saturation solubility,
This insolubility is a fatal disadvantage for crystal growth. Group III nitrides conventionally commercially available are almost in a fine powder state, and have the above-mentioned disadvantages uniformly.
In the mixture of the group III nitride microcrystal powder and the group III metal raw material according to the present invention, since the nitride crystal is synthesized in the group III melt, the surface thereof is completely covered with the group III metal raw material. When used as a liquid phase growth raw material, it is very easy to dissolve, and can reach saturated solubility more easily than conventional raw materials. As a result, the controllability and reproducibility of the epitaxial growth are remarkably improved, and a high-purity group III nitride crystal can be obtained.

Further, in the conventional group III nitride synthesis method, since a group III oxide or chloride is used as a raw material, a step of removing unreacted substances from the synthesized nitride powder is always required. In the production method according to the first, second and fourth aspects of the present invention, since oxides and chlorides are not used as raw materials, unreacted substances do not become impurities during liquid phase growth. The mixture can be directly used as a raw material for liquid phase growth without extracting only the group III nitride when used. The elimination of the extraction step not only leads to a significant shortening of the step, but also eliminates the contamination of the raw material, which tends to occur in the extraction step, and enables high-purity liquid phase growth.

The inventions according to the third to fifth aspects relate to a liquid phase growth method, but the present invention is also applicable to a vapor phase growth method. That is, the invention according to claim 6 is to remove a group III metal raw material from a mixture of a group III nitride microcrystal and a group III metal raw material obtained by the method for manufacturing a nitride crystal according to claim 1 or 2. It is a group III nitride crystal powder obtained by the above method. Using this nitride crystal powder as a starting material, a group III nitride crystal can be grown by vapor phase (claim 7), and a group III nitride crystal can be obtained by the vapor phase growth (claim 7). 8).

According to a ninth aspect of the present invention, there is provided a method for producing a group III nitride crystal, comprising melting, resolidifying or sintering the group III nitride powder according to the sixth aspect. The described invention is a group III nitride crystal obtained by the production method.

In the method for manufacturing a nitride crystal according to claim 1 or 2, the group III element is Al, Ga, I
n, and the gas containing a nitrogen atom may be ammonia gas.
1). Further, also in the inventions of claims 3 to 10, the group III element can be any one of Al, Ga, and In.

The second essential point of the present invention is that III such as gallium is used.
A seed crystal or a substrate crystal is immersed in a melt of a group element, and a bubble of a gas containing nitrogen such as ammonia is intermittently brought into contact with the surface of the group. In this method, a nitride-containing crystal of a group III element is grown on the surface of the gas by reacting a gas containing the same.

In this nitride crystal growth method, a gas containing nitrogen is injected into a group III melt at a temperature much lower than the melting point of the nitride to be synthesized, and a liquid group III element and a gas phase V
It is assumed that a group III element is reacted to directly generate a solid group III nitride crystal in a group III element melt (a nitride melt cannot be formed). This is based on the fact that the solubility of nitrides in Group III element melts is very low, and it is actively utilized, and as described above, the premise itself is the same as that of the injection method described above. This is a crystal growth method based on a new concept completely different from such a melt growth method.

Gallium, aluminum, indium, etc.
A gas containing a Group III element and nitrogen such as ammonia or hydrazine is used at the melting point of nitride (for example, 200 mm for GaN).
Several hundreds or so, which is considerably lower than
It is known that they react at a temperature of about 1000 ° C. to produce a group III nitride. For example, there are the following reports.

"Crystal growth of GaN by reaction be
tween Ga and NH ₃ ”D.E1well et.al., J. Crystal Growth 66 (l984) 45-5
4 However, the generated GaN does not dissolve in the group III melt, but only precipitates as a fine powder on the surface of the group III melt.

In the method for producing a nitride crystal according to claim 12 or 13, a seed crystal or a substrate crystal is immersed in a melt of a group III element such as gallium, and a gas containing nitrogen such as ammonia on the surface thereof. Intermittently. Group III atoms bonded to the surface of the seed crystal or the substrate crystal are nitrided by reacting a group III element with a gas containing nitrogen on the surface of the seed crystal or the substrate crystal, and the nitride crystal is grown on the base. You can go. If this reaction is continuously performed, growth of an epitaxial film and growth of a bulk crystal can be performed.

In the method for producing a nitride crystal according to claim 12 or 13, the group III element is Al, G
The gas containing any one of a and In and containing the nitrogen atom may be an ammonia gas. Further, in the method for producing a nitride crystal according to claim 12 or 13, the temperature of the group III element melt is lower than the melting point of the nitride crystal to be grown (claim 15).

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to examples.

(Example 1) As an example of the present invention, an apparatus as shown in FIG. 1 was manufactured. Using this device, G
An example in which aN microcrystals are synthesized will be described.

3000 g of Ga was placed in a quartz crucible 1 having an inner diameter of 70 mm and a height of 150 mm, and Ga was heated to 950 ° C. by a heater 2 to form a Ga melt 3. Subsequently, ammonia gas was introduced into the Ga melt 3 by using
/ Min for 5 hours. The gas blown into the melt 3 reacts with the melt to generate GaN microcrystals,
Microcrystals emerged on the melt surface. The ammonia gas that has not contributed to the reaction passes through the melt 3 as bubbles,
It exits the space above the container and is discharged out of the container through the exhaust pipe 5. The discharged ammonia gas was released to the atmosphere through a wet type abatement system. After gas injection for 5 hours, the gas to be injected was switched to nitrogen, and the Ga melt was cooled to room temperature.

When the cooled Ga melt was taken out of the container and observed, a large amount of GaN microcrystals floated above the Ga melt. The surface of the GaN microcrystal was completely wet with the Ga melt. As for the Ga melt, a weight increase of 10.2 g was observed before and after the synthesis operation. Calculating from this, 61 g of GaN microcrystals could be synthesized.

(Example 2) As in Example 1, GaN
A microcrystal is synthesized, and the Ga melt and G floating above the Ga melt
Liquid phase epitaxial growth of GaN was performed by a slide boat method using a mixture of aN microcrystals as a raw material. FIG. 2 shows a schematic sectional view of the apparatus used for the growth. A graphite boat 11 was charged with 20 g of a mixture of a Ga melt and a GaN crystal as a raw material 12. 25mm for slide boat 17
An angular c-plane sapphire substrate 16 was set. The inside of the quartz reaction tube 14 was set to a nitrogen gas atmosphere, and the raw material was heated by the heater 13 until the output of the thermocouple 15 reached 1150 ° C. After leaving for 4 hours in this state, the temperature was lowered to 1100 ° C.
The slide boat 17 was moved by pulling the operation rod 18, and the sapphire substrate 16 was brought into contact with the raw material 12. From now on,
Lower the temperature of the raw material to 600 ° C at a rate of 1 ° C per minute,
8, the slide boat 17 was returned to the original position, and the substrate 16 and the raw material 12 were separated. Thereafter, the heater power was turned off and the system was cooled to room temperature. FIG. 3 shows a temperature program during liquid phase epitaxial growth.

After the growth, the substrate was taken out, and the surface and cross section were observed. A transparent film had grown on the surface of the sapphire substrate. The film thickness determined from SEM observation of the cross section was 4.
It was 2 μm. FIG. 4 shows the photoluminescence measurement results of the grown film at room temperature. A sharp emission peak at 360 nm corresponding to GaN band edge emission was observed, confirming that the grown film was a good quality GaN film. When the electrical characteristics of the grown film were measured by a Van der Pauw method, the carrier concentration was 1 × 10 ¹⁷ cm ⁻³ and the mobility was 520 cm ² / V · sec, showing good characteristics.

Example 3 In the same manner as in Example 1, 20 mg of Si was previously added to the raw material Ga to synthesize GaN microcrystals, and a mixture of the obtained Ga melt and GaN microcrystals was used as the raw material. And G in the slide boat method similar to that of the second embodiment.
Liquid phase epitaxial growth of aN was performed.

FIG. 5 shows the photoluminescence measurement results at room temperature of the obtained GaN film. A sharp emission peak at 369 nm corresponding to the emission of Si-doped GaN was observed,
It was confirmed that the grown film was doped with Si.
When the carrier concentration of the grown film was measured by the van der Pauw method, it was 6 × 10 ¹⁸ cm ⁻³ of n-type.

(Example 4) In the same manner as in Example 1, GaN microcrystals were synthesized by previously adding 7 mg of Mg to the raw material Ga, and a mixture of the obtained Ga melt and GaN microcrystals was used as the raw material. In the same manner as in the second embodiment, Ga
N liquid phase epitaxial growth was performed.

FIG. 6 shows the photoluminescence measurement results of the obtained GaN film at room temperature. An emission peak at 445 nm corresponding to the emission of Mg-doped GaN was observed, confirming that the grown film was doped with Mg. When the carrier concentration of the grown film was measured by the Van Der Poe method, it was p-type 5 × 10 ¹⁷ cm ⁻³ . In the Mg-doped GaN film obtained by this method, the film obtained by MOVPE growth does not activate Mg in the crystal and does not show p-type electric characteristics unless heat treatment is applied. Good p-type electrical characteristics were exhibited. This is presumably because there was no mixing of hydrogen atoms that hinder Mg activation.

Example 5 A mixture of undoped GaN microcrystals and metallic Ga synthesized in the same manner as in Example 1 was collected, and hydrochloric acid and hydrogen peroxide were added thereto to dissolve only Ga. Only GaN crystals were taken out by filtration with filter paper. The filtered powder was sufficiently washed with pure water, and then dried in a vacuum high-temperature bath. As a result, 61 g of grayish white powder
Obtained. When this powder was observed with a microscope, the particle size was
It consisted of microcrystals based on hexagonal prisms of about 10 μm. Figure 7 shows the photoluminescence measurement results of this powder at room temperature.
Shown in A sharp emission peak at 360 nm corresponding to the band edge emission of GaN was observed, and the obtained crystal was found to be of good quality.
N was confirmed. The concentration of impurities that could be mixed into the obtained powder was determined by secondary ion mass spectrometry (SI
MS), it was found that Si
^Were all below the detection limit except that about 5 × 10 ¹⁵ cm ⁻³ was detected.

(Example 6) Using the GaN microcrystalline powder obtained in Example 5 as a raw material,
N vapor phase epitaxial growth was performed. Into a quartz crucible 23 having a diameter of 50 mm, GaN microcrystalline powder 26
5 g was put in the quartz container 21 and supported by the graphite susceptor 25. On the other hand, a 25 mm square c-plane sapphire substrate 28 is placed on a substrate holder 22 made of graphite.
, And the substrate was suspended in the quartz crucible 23 so that the substrate surface was opposed to the raw material 26. In this state, the inside of the quartz container 21 is replaced with an ammonia gas atmosphere, and the heater 24 is continuously supplied with the ammonia gas at a rate of 0.5 liter per minute.
To heat the raw material. Heating is performed by a thermocouple 2 placed under the crucible.
The output of 7 was controlled to be 1100 ° C. At this time, the surface temperature of the substrate 28 was about 850 ° C. The crystal growth was performed by holding the raw material for 24 hours while heating and sublimating the raw material.

On the surface of the sapphire substrate taken out, a transparent GaN film had grown. When the surface of the GaN film was observed with a microscope, a morphology having a triangular to hexagonal shape was observed. The average thickness of the grown film was about 400 μm. When the electrical characteristics of the grown film were measured by the Van Der Poe method, the carrier concentration was 2 × 10 ¹⁷ cm ⁻³ and the mobility was 490 cm ² / V · sec.

(Embodiment 7) In the same manner as in Embodiment 1, G
InN was synthesized using In instead of a. The conditions were the same as in Example 1 except that the synthesis temperature was set to 600 ° C. The synthesized In was cooled to 180 ° C., and a mixture of InN microcrystals and metal In floating above the In melt was taken out before the In was solidified.

Hydrochloric acid and hydrogen peroxide were added to the mixture to dissolve only In, and then filtered through a filter paper to extract only InN microcrystals. The filtered powder was sufficiently washed with pure water, and then dried in a vacuum high-temperature bath. As a result, about 200 g of a light grayish white powder was obtained. When this powder was observed with a microscope, it was found to be composed of hexagonal prism-based microcrystals having a particle size of about 8 μm. When the photoluminescence spectrum of the obtained powder was measured, emission of 650 nm corresponding to InN band edge emission was observed.

(Modification) In the above embodiment, the crystal growth of InN has been described mainly with respect to the crystal growth of GaN. However, the crystal growth of AlN, AlGaN or a mixed crystal of AlN or InN, such as AlGaN or GaInN, is also described. Can also be applied.

As the gas containing nitrogen, hydrazine, monomethylhydrazine and the like can be used in addition to ammonia.

Although the embodiment of liquid phase growth has been described with reference to crystal growth under atmospheric pressure, the crystal growth rate can be further increased by performing the growth under a high pressure in a nitrogen or ammonia atmosphere.

In the embodiments of the liquid phase growth and the vapor phase growth, the epitaxial growth on the sapphire substrate has been described. However, the application to the epitaxial growth using another substrate and the bulk crystal growth of nitride is also possible. .

The yield and particle size of the nitride microcrystals obtained by the synthesis can be controlled by the residence time of the gas such as ammonia injected into the group III melt. Therefore, a modified example of changing the tip shape of the gas injection pipe or providing a path through which gas bubbles pass in the melt by quartz work or the like is conceivable.

(Other Embodiments) The nitride microcrystals obtained according to the present invention can be widely applied as semiconductor materials and phosphor materials. In particular, the liquid phase growth method according to one aspect of the present invention is effective when applied to the production of a light emitting element from ultraviolet to yellow.

For example, if the liquid phase growth apparatus described in the second embodiment is provided with two raw material storage sections, one of which stores the Mg-doped GaN raw material and the other stores the Si-doped GaN raw material, the p-type substrate is formed on the substrate. An n-type GaN film can be continuously grown. L is added to the epitaxial growth substrate thus obtained.
By performing the ED manufacturing process, the pn junction type blue L can be easily formed.
An ED can be manufactured. According to this method, an LED can be manufactured more easily, safely and inexpensively than the conventional MOVPE method. In addition, conventional MOVPE growth G
In the case of aN, heat treatment must be performed later to produce a p-type crystal, and therefore, there is a restriction that the element structure must be designed so that the crystal surface is always p-type. When the liquid phase epitaxial growth method according to the present invention is used, p-type conductivity can be obtained without performing heat treatment, so that the margin of the structural design of the element becomes very large.

Since the synthesis temperature and atmospheric pressure of the nitride, the amount of the raw material used, and the like differ depending on the type of the nitride to be synthesized and the type of the raw material to be used, it is difficult to uniquely determine the optimum conditions. .

(Embodiment 8) As an eighth embodiment of the present invention, an apparatus as shown in FIG. 9 was manufactured. An example in which a GaN crystal is grown using this apparatus will be described.

In a quartz container 31 having an inner diameter of 70 mm and a height of 200 mm, 3000 g of the melted Ga33 is accommodated. Fixed.
In this state, the molten Ga 33 is heated by the heater 32,
The output was controlled to be 1000 ° C. by the thermocouple 37.

Subsequently, ammonia gas was continuously introduced from the bottom of the quartz container at a rate of 0.2 liter / min for 76 hours through a quartz ammonia introducing tube 36 having an inner diameter of 6 mm. The ammonia gas introduced into the molten Ga 33 rises as bubbles in the melt. The number of bubbles was about 350 per minute. Ammonia gas bubbles rising in the melt
It hits the surface of the seed crystal 35, and the Ga
N crystals are generated. Unreacted ammonia gas directly reaches the molten Ga surface as bubbles and is discharged out of the container. The discharged gas was harmed by a wet scrubber and released to the atmosphere. The ammonia gas bubbles reacted with Ga even on the surface other than the surface of the seed crystal to generate GaN. This GaN was microcrystals having a diameter of about several μm and floated on the surface of the molten Ga, and did not contribute to the growth on the seed crystal.

The crystal after growth was cooled, taken out of the molten Ga, and the metal Ga adhering to the surface was washed off with hydrochloric acid. As a result, a hexagonal columnar GaN crystal having a diameter of about 10 mm and a height of about 6 mm was obtained on the seed crystal of SiC.
The obtained crystals had a clear yellow-brown color. The obtained crystal was confirmed to be a GaN crystal by an X-ray diffraction method. The full width at half maximum (FWHM) of the X-ray diffraction peak is about 2 mi
n, and it can be said that the obtained crystals have good crystallinity.

FIG. 10 shows the photoluminescence measurement results at room temperature of the obtained crystal. A sharp emission peak corresponding to the band-edge emission of undoped GaN was observed at 360 nm, and it was confirmed by photoluminescence measurement that the crystal was a good-quality GaN crystal.

(Embodiment 9) As a ninth embodiment of the present invention, an apparatus as shown in FIG. 11 was manufactured. An example in which GaN crystal is epitaxially grown using this apparatus will be described.

A quartz crucible 45 having an inner diameter of 70 mm and a height of 150 mm
Into the graphite susceptor 44 and the stainless steel container 4
3 was installed inside. The quartz crucible 45 contains 3000 g of molten Ga48, and a c-plane sapphire single crystal substrate (hereinafter, referred to as a sapphire substrate) 49 having a side length of 25 mm is attached to the tip of the substrate support jig 47 in the molten Ga48. did. The sapphire substrate 49 was fixed by being inclined from horizontal by several degrees in molten Ga. In addition, molten Ga
Inside the tube 48, an ammonia gas inlet tube 41 made of quartz whose tip was bent into a J-shape was installed. The tip of the gas introduction pipe 41 is
The sapphire substrate 49 was fixed directly below the lower end. In this state, the molten Ga 48 was heated by the heater 42, and the output of the thermocouple 46 was controlled to 950 ° C. Subsequently, the ammonia gas is supplied to the ammonia introducing pipe 41.
, And introduced into molten Ga48 at a rate of 0.1 liter per minute for 1 hour. The introduced ammonia gas rises as bubbles in the melt. The number of bubbles is about 20 per minute
There were zero. The bubbles of the ammonia gas rising in the melt hit the lower end of the sapphire substrate 49 and rose along the substrate surface, reached the molten Ga 48 surface, and were discharged out of the container. The discharged gas was harmed by a wet scrubber and released to the atmosphere.

The crystal after growth is cooled, and molten Ga4
8 and the metal Ga adhering to the surface was washed away with hydrochloric acid. As a result, a transparent crystal thin film having a thickness of about 4 μm was obtained on the surface of the sapphire substrate 49. The obtained crystal was confirmed to be a GaN crystal by an X-ray diffraction method. The full width at half maximum (FWHM) of the X-ray diffraction peak is about 5 mi
n.

FIG. 12 shows the results of photoluminescence measurement of the obtained crystal at room temperature. A sharp emission peak corresponding to the band-edge emission of undoped GaN was observed at 360 nm, confirming that the GaN crystal was of good quality.

The growth temperature of the nitride crystal, the atmospheric pressure during the growth, the amount of the raw material used, and the like differ depending on the type of the nitride to be grown and the type of the raw material to be used, and therefore cannot be uniquely determined.

Ammonia is selected as the nitrogen-containing gas because it is chemically active to some extent and is based on the results of consideration of safety and economy. In principle, however, a gas such as hydrazine or monomethylhydrazine is used. Can also be used. However, these gases are far more explosive than ammonia.

The reason why the temperature of the group III source material during the crystal growth is set to be equal to or lower than the melting point of the nitride to be grown is to prevent the grown crystal from being decomposed or remelted.

(Modification) In the embodiment, the crystal growth of GaN has been described. However, the present invention can also be applied to the crystal growth of InN, AlN, or a mixed crystal thereof such as AlGaN and GaInN. Furthermore, a nitride crystal doped with an impurity can be grown by mixing an impurity element into a group III melt or a gas containing nitrogen.

As the gas containing nitrogen, hydrazine, monomethylhydrazine and the like can be used in addition to ammonia.

The shape of the tip of the tube for introducing a gas such as ammonia into the Group III melt can be variously modified in order to control the size and number of gas bubbles in the melt. For example, a plurality of gas outlets can be provided at the tip of the gas introduction pipe, or a net can be provided at the tip of the gas introduction pipe.

A modification in which a plurality of seed crystals or substrate crystals are provided in the group III melt is also conceivable.

In the embodiments shown in FIG. 1, FIG. 2, FIG. 8, FIG. 9 and FIG. 11, only the crystal growth vessel showing the essential part of the present invention has been described.
By constructing a system combining a mass flow controller for adjusting the gas flow rate and a temperature controller capable of automatically controlling the temperature of the heater, the control of crystal growth becomes easier.

The nitride crystal obtained by the present invention can be widely applied as a semiconductor material and a phosphor material. In particular, a nitride bulk single crystal substrate is most suitable as a substrate material when manufacturing a blue laser diode.

[0073]

As described above, according to the present invention, the following excellent effects can be obtained.

(1) According to the production method of the present invention, a gas containing nitrogen is injected into the group III melt at a temperature much lower than the melting point of the nitride to be synthesized. Since the group III element in the phase reacts with the group V element in the gas phase to directly generate the group III nitride crystal in the solid phase in the melt of the group III element, it is simpler than in the case of making a melt of nitride. It can be easily and inexpensively mass-produced with a simple apparatus in a short time.

(2) The mixture of the group III nitride microcrystals and the group III metal raw material according to claim 3 of the present invention has a completely complete surface because the nitride microcrystals are synthesized in the group III melt. II
When the mixture is covered with a group I metal material and this mixture is used as a liquid phase growth material, it is very easily dissolved, and a solution having a saturated solubility can be easily obtained as compared with conventional materials. As a result, the controllability and reproducibility of epitaxial growth are dramatically improved.

(3) According to the growth method according to claims 4, 7 and 9, of the present invention, a group III high-purity nitride semiconductor crystal can be easily and inexpensively mass-produced in a short time with a simple apparatus. can do. Further, it is safe because there is no need to use dangerous gases such as chlorine conventionally used in the HVPE method and organic metals used in the MOVPE method. Further, according to the growth method of the present invention, the liquid crystal growth or the gas phase growth of the nitride crystal, which has been particularly difficult in the past, can be easily performed. As a result, it is easy to manufacture a device having a high-carrier p-type crystal without special treatment of the nitride crystal, and it is not necessary to bring the p-type conductive layer to the element surface. The degree of freedom of design is expanded.

(4) In the method for growing a nitride according to the fourth, seventh and ninth aspects of the present invention, since an oxide or chloride is not used as a raw material as in the conventional method, unreacted substances are formed in a liquid phase. The mixture can be directly used as a raw material for liquid phase growth without being an impurity during the growth, and thus without extracting only the group III nitride when used as a raw material for liquid phase growth. The elimination of the extraction step not only leads to a significant shortening of the step, but also eliminates the contamination of the raw material, which tends to occur in the extraction step, and enables high-purity liquid phase growth.

(5) Claims 12 and 13 of the present invention
According to the manufacturing method described above, it becomes possible to grow a group III nitride semiconductor crystal, particularly a bulk single crystal that could not be grown conventionally. The use of this crystal for the substrate is not only effective for increasing the efficiency and extending the life of the blue LED, but also greatly contributing to promoting the practical use of a blue LD that has not yet been commercialized. Also such III
A group III nitride semiconductor crystal can be easily and inexpensively grown with a simple device. In addition, it is safe because there is no need to use gases such as chlorine conventionally used in the HVPE method and dangerous raw materials such as organic metals used in the MOVPE method.

[Brief description of the drawings]

FIG. 1 shows GaN according to first and seventh embodiments of the present invention.
It is a cross section of a crystal synthesizer.

FIG. 2 is a schematic sectional view of a GaN crystal liquid phase growth apparatus according to a second embodiment of the present invention.

FIG. 3 is a graph showing a temperature program during liquid phase growth of a GaN crystal according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a photoluminescence measurement result at room temperature of a liquid phase epitaxially grown undoped GaN conjunctive film according to a second example of the present invention.

FIG. 5 is a diagram showing a photoluminescence measurement result at room temperature of a liquid phase epitaxially grown Si-doped GaN crystal film according to a third example of the present invention.

FIG. 6 is a diagram showing a photoluminescence measurement result at room temperature of a liquid phase epitaxially grown Mg-doped GaN crystal film according to a fourth example of the present invention.

FIG. 7 shows an undoped Ga according to a fifth embodiment of the present invention.
It is a figure which shows the photoluminescence measurement result at room temperature of N microcrystal powder.

FIG. 8 is a schematic cross-sectional view of a GaN crystal vapor phase growth apparatus according to a sixth embodiment of the present invention.

FIG. 9 is a schematic sectional view of a GaN crystal growth apparatus according to an eighth embodiment of the present invention.

FIG. 10 is a diagram showing a photoluminescence measurement result at room temperature of a GaN crystal produced in an eighth example of the present invention.

FIG. 11 is a schematic sectional view of a GaN crystal epitaxial growth apparatus according to a ninth embodiment of the present invention.

FIG. 12 is a diagram showing a photoluminescence measurement result at room temperature of a GaN epitaxial growth crystal manufactured in a ninth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Quartz crucible 2 Heater 3 Ga melt 4 Ammonia gas injection pipe 5 Exhaust pipe 6 Thermocouple 11 Graphite boat 12 Mixture of GaN fine powder and Ga 13 Heater 14 Quartz reaction tube 15 Thermocouple 16 Sapphire substrate 17 Graphite slide boat 18 Quartz Operation rod 21 Quartz container 22 Graphite substrate holder 23 Quartz crucible 24 Heater 25 Graphite susceptor 26 GaN microcrystalline powder 27 Thermocouple 28 Sapphire substrate 31 Quartz container 32 Heater 33 Melted Ga 34 Seed crystal support jig 35 Seed crystal 36 Ammonia Inlet pipe 37 with thermoelectric

Claims (15)

[Claims] A group III metal element is heated and melted, and a gas containing a nitrogen atom is injected into a melt of the group III metal element at a temperature lower than the melting point of the nitride to be obtained. A method for producing a nitride crystal, comprising producing a group III nitride microcrystal in a melt of an element. 2. The method for producing a nitride crystal according to claim 1, wherein an impurity element is mixed with the group III metal element to produce a group III nitride crystal doped with the impurity element. A method for producing a nitride crystal. 3. A mixture of a Group III nitride microcrystal and a Group III metal element obtained by the method for producing a nitride crystal according to claim 1 or 2. 4. A method for producing a nitride crystal according to claim 1 or 2, wherein a mixture of a group III nitride microcrystal and a group III metal element is used as a starting material.
Liquid phase growth method for group III nitride crystals. 5. A method for producing a nitride crystal according to claim 1 or 2, wherein said mixture is obtained by a liquid phase growth method using a mixture of group III nitride microcrystals and a group III metal element as a starting material. Group III nitride crystal. 6. A group III metal element obtained by removing a group III metal element from a mixture of a group III nitride microcrystal and a group III metal element obtained by the method for producing a nitride crystal according to claim 1 or 2. Nitride crystal powder. 7. A method for vapor-phase growing a group III nitride, comprising using the group III nitride crystal powder according to claim 6 as a starting material. 8. A group III nitride obtained by a vapor phase growth method of a group III nitride using the group III nitride powder according to claim 6 as a starting material.
Group I nitride crystal. 9. A method for producing a group III nitride crystal, comprising melting, resolidifying or sintering the group III nitride crystal powder according to claim 6. 10. A group III nitride crystal obtained by melting, resolidifying or sintering the group III nitride crystal powder according to claim 6. 11. The method for producing a nitride crystal according to claim 1, wherein the group III element is any one of Al, Ga, and In, and the gas containing a nitrogen atom is an ammonia gas. A method for producing a nitride crystal. 12. A seed crystal is immersed in a heated and melted Group III element, and gas bubbles containing a nitrogen atom are intermittently brought into contact with the surface of the seed crystal in the Group III element to thereby form the seed crystal. A method for producing a nitride crystal, comprising growing a nitride crystal of a group III element on a surface. 13. A substrate crystal is immersed in a heated and melted group III element, and gas bubbles containing a nitrogen atom are intermittently brought into contact with the surface of the substrate crystal in the group III element.
A method for producing a nitride crystal, comprising epitaxially growing a group III element nitride single crystal on the substrate crystal surface. 14. The method for producing a nitride crystal according to claim 12, wherein said group III element is Al, Ga, In.
Wherein the gaseous substance containing a nitrogen atom is ammonia gas. 15. The method for producing a nitride crystal according to claim 12, wherein the temperature of said group III element melt is lower than the melting point of the nitride crystal to be grown. Method.