JP2001058900A - Crystal of nitride of group iii, crystal growth crystal growth apparatus and semiconductor device of nitride of group iii - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a crystal of nitride of group III having a practical side for manufacturing a device such as a high-performance light emitting diode, LD, etc., and provide both a method and an apparatus for crystal growth, capable of growing the crystal of nitride of group III. SOLUTION: In this crystal growing apparatus for subjecting crystal of nitride of group III to crystal growth by using at least a flux (e.g. metal Na or a compound containing Na), a metal of group III (e.g. Ga (gallium)) and nitrogen or a nitrogen-containing compound, a region 102 for crystal growth of the crystal of nitride of group III (e.g. GaN crystal) is separated from regions 103 and 108 to which a metal of group III (e.g. gallium) and nitrogen (N) or a nitrogen (N)-containing compound are supplied in a reaction container whose temperature and pressure are controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a group III nitride crystal, a crystal growth method, a crystal growth apparatus, and a group III nitride semiconductor device.

[0002]

2. Description of the Related Art Most of InGaAlN-based (III-nitride) devices currently used as violet-blue-green light sources are MOC on sapphire or SiC substrates.
It is produced by crystal growth using VD (metal organic chemical vapor deposition), MBE (molecular beam crystal growth), or the like.
When sapphire or SiC is used as the substrate, III
Crystal defects due to a large difference in thermal expansion coefficient and lattice constant from group nitrides increase. For this reason, there are problems in that the device characteristics are poor, for example, it is difficult to extend the life of the light emitting device, and the operating power increases.

When applied to electronic devices,
High-concentration crystal defects serve as a path for leakage current, which causes deterioration of characteristics. Further, in the case of a field effect transistor using a two-dimensional electron gas, there are the following problems. That is, when a defect occurs in the transistor structure, lattice relaxation is performed. In the GaN system, the confinement effect of the two-dimensional electron gas is promoted by the piezoelectric field effect. However, when lattice relaxation due to defects occurs, the confinement effect is reduced. As a result, the two-dimensional electron mobility decreases, and the transistor characteristics deteriorate.

Further, in the case of a sapphire substrate, since it is insulative, it is impossible to take out an electrode from the substrate side as in a conventional light emitting device. Required. As a result, there is a problem in that the device area increases and the cost increases. In addition, II fabricated on a sapphire substrate
It is difficult to separate a group I nitride semiconductor device by cleavage, and it is not easy to obtain a cavity facet required for a laser diode (LD) by cleavage. For this reason, at present, a resonator end face is formed by dry etching or a sapphire substrate is polished to a thickness of 100 μm or less, and then a resonator end face is formed in a form close to cleavage. Also in this case, it is impossible to easily separate the end face of the resonator from the chip as in the conventional LD in a single process, which leads to a complicated process and a high cost.

[0005] In order to solve this problem, it has been proposed to reduce the crystal defects by performing selective lateral growth and other processes of a group III nitride semiconductor film on a sapphire substrate.

For example, the reference "Japanese Journal of App
lied Physics Vol.36 (1997) Part 2, No.12A,
L1568-1571 "(hereinafter, referred to as a first conventional technique) shows a laser diode (LD) as shown in FIG. In the laser diode of FIG. 9, a GaN low-temperature buffer layer 2 and a GaN layer 3 are sequentially grown on a sapphire substrate 1 by an MOVPE (metal organic chemical vapor deposition) apparatus, and then a SiO ₂ mask 4 for selective growth is formed. This SiO ₂ mask 4
Is formed through a photolithography and etching process after depositing a SiO ₂ film by another CVD (chemical vapor deposition) apparatus. Next, the GaN film 3 having a thickness of 20 μm is grown on the SiO ₂ mask 4 again by the MOVPE apparatus, so that GaN is selectively grown in the lateral direction and a case where the selective lateral direction growth is not performed. Thus, crystal defects are reduced. Further, by introducing the modulation-doped strained superlattice layer (MD-SLS) 5 formed thereon, it is possible to prevent crystal defects from extending to the active layer 6. As a result, the device lifetime can be extended as compared with the case where the selective lateral growth and the modulation-doped strained superlattice layer are not used.

In the case of the first prior art, it is possible to reduce crystal defects as compared with a case where a GaN film is not selectively grown in a lateral direction on a sapphire substrate. The aforementioned problems with insulation and cleavage remain. Furthermore, SiO ₂
The crystal growth by the MOVPE apparatus is required twice with the mask forming step interposed therebetween, which causes another problem that the step becomes complicated.

As another method, for example, the document “Appl
ied Physics Letters, Vol. 73, No. 6, P832-834 (1
998) "(hereinafter, referred to as a second conventional technique) proposes applying a GaN thick film substrate. In the second prior art, after the 20 μm selective lateral growth of the first prior art, a 200 μm GaN thick film is grown by an H-VPE (hydride vapor phase epitaxy) apparatus, and thereafter, the GaN thick film is grown. The grown GaN film has a thickness of 150 μm,
A GaN substrate is manufactured by polishing from the sapphire substrate side. Using a MOVPE apparatus on this GaN substrate, crystal growth required as an LD device is sequentially performed,
Create an LD device. As a result, in addition to the problem of crystal defects, it is possible to solve the above-mentioned problems relating to insulation and cleavage caused by using a sapphire substrate.

[0009] However, the second prior art has a more complicated process than the first prior art, resulting in higher cost. In addition, the second prior art method uses
When a GaN thick film having a thickness of 00 μm is grown, a stress caused by a difference in lattice constant and a difference in thermal expansion coefficient from sapphire as a substrate becomes large, and a new problem that cracks occur. Therefore, it is difficult to increase the area, which leads to a further increase in cost.

On the other hand, the literature "Journal of Crystal Grow"
th, Vol.189 / 190, p.153-158 (1998) "
(Hereinafter referred to as the prior art) proposes growing a GaN bulk crystal and using it as a homoepitaxial substrate. This technique is a technique of growing GaN from liquid Ga at a high temperature of 1400 to 1700 ° C. and a nitrogen pressure of an extremely high pressure of several tens of kbar. In this case, a group III nitride semiconductor film required for a device can be grown using the bulk-grown GaN substrate. Therefore, a GaN substrate can be provided without complicating the process unlike the first and second prior arts.

However, the third prior art has a problem in that crystal growth at a high temperature and a high pressure is required, and a reaction vessel capable of withstanding the growth is extremely expensive. In addition, even with such a growth method, the size of the obtained crystal is at most about 1 cm, which is too small for practical use of the device.

As a method for solving the problem of the GaN crystal growth at a high temperature and a high pressure, reference is made to “Chemistry of Mat”.
erials Vol. 9 (1997) p. 413-416 ”(hereinafter, referred to as a fourth conventional technique) includes G using Na as a flux.
An aN crystal growth method has been proposed. This method uses sodium azide (NaN ₃ ) as a flux and metallic Ga
Is sealed in a stainless steel reaction vessel (inside dimensions: inner diameter = 7.5 mm, length = 100 mm) in a nitrogen atmosphere, and the reaction vessel is kept at a temperature of 600 to 800 ° C. for 24 to 100 hours. Thereby, a GaN crystal is grown. In the case of the fourth prior art,
It is characterized in that crystal growth can be performed at a relatively low temperature of about 600 to 800 ° C., and the pressure in the vessel can be as low as about 100 kg / cm ^2, which is lower than that of the third conventional technique. However, a problem with this method is that the size of the obtained crystal is small to less than 1 mm. Such a size is too small, as in the case of the third prior art, to make the device practical.

[0013]

SUMMARY OF THE INVENTION The present invention is directed to a first and a second invention.
Without complicating the process which is a problem of the prior art, without using an expensive reaction vessel which is a problem of the third conventional technology, and without using a crystal which is a problem of the third or fourth conventional technology. Provide a group III nitride crystal of a practical size for producing optical devices and electronic devices such as high performance light emitting diodes and LDs without reducing the size of
Another object of the present invention is to provide a crystal growth method and a crystal growth apparatus capable of growing such a group III nitride crystal, and to provide a high-performance group III nitride semiconductor device.

[0014]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 includes at least a reactor
It contains a group III metal and a flux, and is characterized in that nitrogen or a compound containing nitrogen is introduced into the reaction vessel from outside the reaction vessel in order to grow a group III nitride crystal.

According to a second aspect of the present invention, there is provided a group III nitride crystal in which at least a group III metal and a flux are contained in a reaction vessel, and nitrogen or a compound containing nitrogen is introduced into the reaction vessel. In this case, in order to increase the size of the group III nitride crystal, during the growth of the crystal of the group III nitride crystal, additionally, a group III metal is additionally supplied. I have.

According to a third aspect of the present invention, there is provided the crystal growth method according to the first or second aspect, wherein the ratio of the group III metal to nitrogen or a compound containing nitrogen is controlled to be constant, and It is characterized in that a crystal is grown.

According to a fourth aspect of the present invention, at least a group III metal and a flux are contained in a reaction vessel, and a reaction is performed from outside the reaction vessel to grow a group III nitride crystal. It is characterized in that a means for introducing nitrogen or a compound containing nitrogen into the container is provided.

According to a fifth aspect of the present invention, in the crystal growth apparatus, at least a group III metal and a flux are contained in a reaction vessel, and nitrogen or a compound containing nitrogen is introduced into the reaction vessel to form a group III nitride. At this time, in order to increase the size of the group III nitride crystal, a means for additionally replenishing the group III metal during the growth of the group III nitride crystal is provided. It is characterized by having.

The crystal growth apparatus according to claim 6 is the crystal growth apparatus according to claim 4 or 5, wherein
When the group I nitride crystal is grown, a means for controlling the ratio of the group III metal to nitrogen or a compound containing nitrogen to be constant is provided.

A crystal growth apparatus according to a seventh aspect of the present invention is a crystal growth apparatus for growing a group III nitride crystal using at least a flux, a group III metal, and nitrogen or a compound containing nitrogen. Is characterized in that a region where a group III nitride crystal is grown is separated from a region where a group III metal and nitrogen or a compound containing nitrogen are supplied in a reaction vessel in which is controlled.

The crystal growth apparatus according to claim 8 is the crystal growth apparatus according to claim 7, further comprising an outer vessel provided outside the reaction vessel, which is necessary for growing a group III nitride crystal. It is characterized in that a region where a high pressure difference between the nitrogen pressure and the atmospheric pressure is generated and a region where the temperature required for growing the group III nitride is attained.

A crystal growth apparatus according to a ninth aspect is characterized in that, in the crystal growth apparatus according to the eighth aspect, nitrogen is introduced between the outer vessel and the reaction vessel. .

Further, the crystal growth apparatus according to claim 10 is
The crystal growth apparatus according to any one of claims 7 to 9, wherein the region in contact with the raw material is covered with a material that does not elute or mix with the raw material and their products.

Further, the group III nitride crystal according to claim 11 is characterized in that the crystal is grown by using the crystal growth method according to any one of claims 1 to 3.

A group III nitride semiconductor device according to a twelfth aspect is fabricated using the group III nitride crystal according to the eleventh aspect.

A group III nitride semiconductor device according to a thirteenth aspect is an optical device.

The group III nitride semiconductor device according to claim 14 is an electronic device.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram (cross-sectional view) showing a configuration example of a crystal growth apparatus according to the present invention. Referring to FIG. 1, this crystal growth apparatus includes a growth vessel 102 for growing a crystal in a reaction vessel 101 having a closed shape made of stainless steel.
Is provided.

Further, the inside space 107 of the reaction vessel 101 is filled with nitrogen (N) gas,
(N) A nitrogen supply pipe 108 is mounted through the reaction vessel 101 so that the pressure can be controlled.
One end of the nitrogen supply pipe 108 is inside the reaction vessel 101, and the other end is outside the reaction vessel 101 and a pressure control device 109.
It is connected to the.

Further, a metal supply pipe 103 for supplying a group III metal (for example, Ga (gallium)) is provided above and spatially separated from the growth vessel 102.

The metal supply pipe 103 and the nitrogen supply pipe 108
The portion in contact with the reaction vessel 101 is spatially isolated from the outside by welding, a metal seal, or the like. The material of the growth vessel 102, the metal supply pipe 103, and the nitrogen supply pipe 108 is stainless steel.

In the growth vessel 102, at the start of the crystal growth of the group III nitride crystal, at least a flux (eg, metal Na or a compound containing Na (eg, sodium azide)) and a group III metal (eg, Ga ( Gallium)). Also, inside the metal supply pipe 103,
There is a space in which a group III metal (for example, Ga (gallium)) 104 can be stored, and a hole 105 is formed at the lowermost end thereof, and an upper end of the metal supply pipe 103 on the side opposite to the hole 105 is provided. Is equipped with a pressurizing device 106 located outside the reaction vessel 101 and capable of applying pressure with a predetermined gas (for example, nitrogen gas or inert gas). That is, the metal supply pipe 103, the hole 105, and the growth vessel 102 are connected to the pressurizing device 10 at the upper end of the metal supply pipe 103.
6 controls the pressure with a high-pressure gas (for example, nitrogen gas or an inert gas) so that the lowermost hole 105
And a group III metal (for example, Ga (gallium)) 104 can be dropped onto the growth vessel 102 from the position shown in FIG.

In the crystal growth apparatus shown in FIG. 1, the temperature of the growth vessel 102 in the reaction vessel 101 and the metal supply pipe 1
The heating means (110, 111) is provided so that the temperature of the region where the group III metal of No. 03 (for example, Ga (gallium)) 104 is stored can be controlled to an arbitrary temperature. I have. Here, the heating means (110, 111)
It comprises a lower heater 110 located below the outside of the reaction vessel 101 and a side heater 111 located outside the side wall of the reaction vessel 101. These heaters 110 and 111 are controlled by a temperature control mechanism (not shown).
The temperature of the growth vessel 102 in the reaction vessel 101 and the group III metal (for example, Ga (gallium)) 1
It is possible to control the temperature of the area in which 04 is stored to an arbitrary temperature.

The crystal growth apparatus shown in FIG. 1 uses at least flux (for example, metallic Na or a compound containing Na) and II
Group I metal (e.g., Ga (gallium)) and nitrogen or a compound containing nitrogen to grow a group III nitride crystal, in a reaction vessel 101 in which temperature and pressure are controlled, A region (102) where a group III nitride crystal (for example, GaN crystal) is grown, and a group III metal (for example,
Ga (gallium)) and regions (103, 108) to which nitrogen (N) or a compound containing nitrogen (N) is supplied are separated. The reaction vessel 101 is provided with a mechanism (110, 111) capable of controlling at least a region including a region (102) where crystal growth is performed at an arbitrary temperature. Further, a mechanism (108, 109) capable of controlling the inside of the reaction vessel 101 to an arbitrary nitrogen pressure is also provided.

FIG. 2 is a diagram (cross-sectional view) showing another configuration example of the crystal growth apparatus according to the present invention. In FIG. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals.

The crystal growth apparatus shown in FIG.
It is the same as the crystal growth apparatus of the above. That is,
Referring to FIG. 2, this crystal growth apparatus also has a growth vessel 102 for growing crystals in a stainless steel closed reaction vessel 101, similarly to the crystal growth apparatus of FIG.

Further, the interior space 107 of the reaction vessel 101 is filled with nitrogen (N) gas,
(N) A nitrogen supply pipe 108 is mounted through the reaction vessel 101 so that the pressure can be controlled.
One end of the nitrogen supply pipe 108 is inside the reaction vessel 101, and the other end is outside the reaction vessel 101 and a pressure control device 109.
It is connected to the.

Further, a metal supply pipe 103 for supplying a group III metal (for example, Ga (gallium)) is provided above and spatially separated from the growth vessel 102.

The metal supply pipe 103 and the nitrogen supply pipe 108
The portion in contact with the reaction vessel 101 is spatially isolated from the outside by welding, a metal seal, or the like. The material of the growth vessel 102, the metal supply pipe 103, and the nitrogen supply pipe 108 is stainless steel.

In the growth vessel 102, at the start of the crystal growth of the group III nitride crystal, at least a flux (eg, metal Na or a compound containing Na (eg, sodium azide)) and a group III metal (eg, Ga ( Gallium)). Also, inside the metal supply pipe 103,
There is a space in which a group III metal (for example, Ga (gallium)) 104 can be stored, and a hole 105 is formed at the lowermost end thereof, and an upper end of the metal supply pipe 103 on the side opposite to the hole 105 is provided. Is equipped with a pressurizing device 106 located outside the reaction vessel 101 and capable of applying pressure with a predetermined gas (for example, nitrogen gas or inert gas). That is, the metal supply pipe 103, the hole 105, and the growth vessel 102 are connected to the pressurizing device 10 at the upper end of the metal supply pipe 103.
6 controls the pressure with a high-pressure gas (for example, nitrogen gas or an inert gas) so that the lowermost hole 105
And a group III metal (for example, Ga (gallium)) 104 can be dropped onto the growth vessel 102 from the position shown in FIG.

In the crystal growth apparatus shown in FIG. 2, the temperature of the growth vessel 102 in the reaction vessel 101 and the group III metal (for example, Ga (gallium)) 10
Heating means (110, 111) so that the temperature of the area where the fluid 4 is stored can be controlled to an arbitrary temperature.
Is provided. Here, the heating means (110, 111)
Is composed of a lower heater 110 located below the outside of the reaction vessel 101 and a side heater 111 located outside the side wall of the reaction vessel 101. These heaters 110 and 111 are controlled by a temperature control mechanism (not shown) to control the temperature of the growth vessel 102 in the reaction vessel 101,
The temperature of the region of the metal supply tube 103 where the group III metal (for example, Ga (gallium)) 104 is stored can be controlled to an arbitrary temperature.

As described above, the crystal growth apparatus shown in FIG.
As in the case of the crystal growth apparatus, at least flux (for example, metal Na or a compound containing Na) and a group III metal
A group III nitride crystal is grown using Ga (gallium) and nitrogen or a compound containing nitrogen, and a group III nitride crystal is grown in a reaction vessel 101 in which temperature and pressure are controlled. Region (102) where crystal growth of a material crystal (for example, GaN crystal) is performed, and a region where a group III metal (for example, Ga (gallium)) and nitrogen (N) or a compound containing nitrogen (N) are supplied ( 103, 108).
The reaction vessel 101 is provided with a mechanism (110, 111) capable of controlling at least a region including a region (102) where crystal growth is performed at an arbitrary temperature. Further, a mechanism (108, 109) capable of controlling the inside of the reaction vessel 101 to an arbitrary nitrogen pressure is also provided.

In the crystal growth apparatus shown in FIG. 2, the reaction vessel 101, the lower heater 110, and the side heater 1 are provided.
An outer container 112 is further provided to cover the outer container 112, the lower heater 110, and the side heater 11.
A heat insulating material 115 is provided between the two.

The metal supply pipe 103 and the nitrogen supply pipe 108 both penetrate the outer vessel 112 and reach the inside of the reaction vessel 101.

Further, in the crystal growth apparatus shown in FIG. 2, the outer container 1 including the heaters 110 and 111 and the heat insulating material 115 is provided.
An arbitrary gas pressure is applied to an area between the reaction vessel 12 and the reaction vessel 101.
(E.g., nitrogen pressure)
A second gas supply pipe (for example, a nitrogen supply pipe) 113 and a pressure control device 114 are provided. That is, the second gas supply pipe 113 is provided so as to penetrate between the outer container 112 and the reaction container 101 from outside the outer container 112.

In the crystal growth apparatus having the configuration shown in FIG. 2, an outer container 112 is provided outside the reaction
Since a gas (for example, nitrogen) having a pressure required to reduce the pressure difference from the nitrogen pressure in the reaction vessel 101 is introduced into the reaction vessel 12, the pressure difference between the inside and the outside of the reaction vessel 101 is reduced by the group III nitride. The pressure difference between the nitrogen pressure and the atmospheric pressure required for growing the crystal can be significantly reduced. Accordingly, the pressure resistance of the reaction vessel 101 is not required, and the reaction vessel 101 only needs to have heat resistance. On the other hand, the outer container 112 is provided with a heat insulating material 115 between the outer container 112 and the lower heater 110 and the side heater 111, so that the heat resistance is not required much, and the group III nitride crystal is not required. It is only necessary to have a pressure resistance enough to withstand a pressure difference between the atmospheric pressure and a pressure substantially equal to the nitrogen pressure necessary for the growth of GaN. In other words, in the apparatus configuration of FIG. 1, the reaction vessel 101 needs to have both heat resistance and pressure resistance, but in the apparatus configuration of FIG. It can be dispersed in the container 112.

As described above, in the crystal growth apparatus shown in FIG. 2, the region where the pressure difference between the nitrogen pressure and the atmospheric pressure necessary for growing the group III nitride crystal is generated (outer vessel 112),
The temperature control and the pressure control can be reliably performed by separating the region (reaction vessel 101) having a temperature required for growing the group I nitride from the region.

That is, in the crystal growth apparatus having the structure shown in FIG. 2, since the heat insulating material 115 is provided between the outer vessel 112 and the lower heater 110 and the side heater 111, the lower heater 110 and the side heater 111 are provided. Temperature control by 111 can be performed more reliably. In the crystal growth apparatus having the configuration shown in FIG.
And the outer container 112 including the heat insulating material 115 and the reaction container 1
A second gas supply pipe (nitrogen supply pipe) 113 and a pressure control device 114 are provided so that an arbitrary gas pressure (for example, nitrogen gas pressure) can be applied to a region between the first gas supply pipe and the first gas supply pipe. Thus, the nitrogen pressure inside the reaction vessel 101 can be more reliably controlled.

In the crystal growth apparatus shown in FIG.
A region where the pressure difference between the nitrogen pressure and the atmospheric pressure necessary for growing the group I nitride crystal is generated (the outer vessel 112), and a region where the temperature required for growing the group III nitride is reached (the reaction vessel 101) ) Can be separated from the cost of the reaction vessel. That is, it is possible to apply an arbitrary pressure from the inside and outside of the reaction vessel to the region of the reaction vessel where the temperature at which the group III nitride crystal grows is obtained. Even with a simple material, the thickness can be reduced, and a crystal growth apparatus can be realized at low cost.

Next, a method of growing a group III nitride crystal using the crystal growth apparatus shown in FIG. 1 or 2 will be described. Raw materials for growing a group III nitride crystal (eg, GaN crystal) include at least flux (eg, metal Na or a compound containing Na), group III metal
(Eg, metallic gallium), nitrogen, or a compound containing nitrogen.

In the crystal growth apparatus shown in FIG. 1 or FIG. 2, a growth vessel 102 is provided in a reaction vessel 101. Initially, as shown in FIG. It contains a flux (eg, sodium azide and metallic sodium) 120 and a Group III metal (eg, metallic gallium) 121. In this state, the nitrogen supply pipe 1
08 to nitrogen or a compound containing nitrogen
And the inside of the reaction vessel 101 is set to a predetermined nitrogen pressure. Then, by raising the temperature of the reaction vessel 101 to a temperature at which the group III nitride crystal grows by the heating means (110, 111), the group III nitride crystal (for example, GaN) 116 is started to grow.

At this time, the amount of nitrogen in the reaction vessel 101 is II
Since the growth of the group I nitride crystal 116 decreases as the growth proceeds, and the nitrogen pressure in the reaction vessel 101 decreases, the nitrogen pressure in the reaction vessel 101 is prevented from decreasing, and the nitrogen pressure in the reaction vessel 101 is constantly reduced. To be almost constant,
During crystal growth, the nitrogen supply pipe 1 is
08 to nitrogen or a compound containing nitrogen
Introduce within. That is, the nitrogen pressure in the reaction vessel 101 is controlled by adding an optional amount of additional raw material with nitrogen or a compound containing nitrogen from the nitrogen supply pipe 108. Thereby, it is possible to keep the nitrogen pressure in the reaction vessel 101 almost constant at all times, and to continue the growth of the group III nitride crystal 116 continuously. Further, a group III metal (for example, metal gallium) is additionally supplied into the reaction vessel 101 from the metal supply pipe 103 in an arbitrary amount. Thereby, a group III nitride crystal (for example, a GaN crystal) can be largely grown.

FIG. 5 shows GaN against Ga / (Na + Ga).
FIG. 4 is a diagram showing the composition, that is, the relationship of Ga / N, using the nitrogen pressure a in the reaction vessel 101 as a parameter. From FIG. 5, it can be seen from FIG.
/ N so that / N always becomes “1”.
1 and the nitrogen pressure within 1 needs to be continuously controlled. That is, in the present invention, the group III nitride crystal is grown by controlling the ratio of the group III metal to nitrogen or a compound containing nitrogen to be constant.

More specifically, a method of growing a group III nitride crystal using the crystal growth apparatus shown in FIG. 2 will be described. Initially, flux as a part of the raw material
(E.g. sodium azide and metallic sodium) and III
Group metal (metal gallium) is contained. Further, inside the metal supply pipe 103 for supplying the group III metal,
A group I metal (metal gallium) 104 is put in, and the inside of the metal supply pipe 103 is pressurized by the pressurizing device 106 at the upper end of the metal supply pipe 103 so that the metal gallium 104 can be supplied. Further, inside the reaction vessel 101,
Through a nitrogen supply pipe 108 and a pressure control device 109,
Nitrogen is pressurized and can be supplied. In the crystal growth apparatus of FIG. 2, the outer vessel 112 and the reaction vessel 101 are further provided.
Between the second gas supply pipe (for example, nitrogen supply pipe)
Pressurized by 113 and pressure control device 114.
At this time, the gas pressures in the three regions of the inside of the reaction vessel 101, the area between the outer vessel 112 and the reaction vessel 101, and the inside of the metal supply pipe 103 by the pressurizing device 106 are controlled to be substantially the same. Have been.

In this state, the temperature inside the reaction vessel 101 is set to II by the lower heater 110 and the side heater 111.
The temperature is raised to a temperature at which GaN, which is a group I nitride, starts crystal growth. Also at this time, the gas pressures in the three regions are controlled so as to be substantially the same. This Ga
Until the crystal growth of N starts, the gas pressure from above the metal supply pipe 103 is controlled so that the metal gallium 104 does not drop from the hole 105 of the metal supply pipe 103.

Next, after the growth of the GaN crystal 116 starts, the gas pressure from above the metal supply pipe 103 is controlled so that the metal gallium 104 drops from the hole 105 of the metal supply pipe 103, The pressure of the nitrogen applied to the reaction vessel 101 is controlled by the pressure control device 109 through the supply pipe 108. As a result, the raw material Ga
(Gallium) and nitrogen (N) are intermittently supplied, and the growth of the GaN crystal 116 in the growth vessel 102 continues. During this time, the temperature inside the growth vessel 102 is controlled by the heater 110 and the side heater 111.

As described above, according to the present invention, the reaction vessel 101
At least a group III metal and a flux are accommodated therein, and nitrogen or a compound containing nitrogen is introduced into the reaction vessel 101 from outside the reaction vessel 101 in order to grow a group III nitride crystal. ing. By introducing nitrogen or a compound containing nitrogen into the reaction vessel 101 from outside the reaction vessel 101, even if the growth of the group III nitride crystal progresses and the amount of nitrogen in the reaction vessel 101 decreases, the reaction vessel 101 It is possible to constantly control the amount of nitrogen in the inside. The means for introducing nitrogen or a compound containing nitrogen into the reaction vessel 101 from the outside of the reaction vessel 101 is a nitrogen supply pipe 108 in the example of FIGS.
And a pressure control device 109.

In the present invention, the reaction vessel 101 is
At least a group III metal and a flux are accommodated, and nitrogen or a compound containing nitrogen is introduced into the reaction vessel 101 to grow a group III nitride crystal. In order to increase the size of the crystal, when growing a group III nitride crystal,
Additional group II metals are now provided. During the crystal growth of the group III nitride crystal, the size of the group III nitride crystal can be increased by additionally supplying a group III metal. The means for additionally replenishing the group III metal is the metal supply pipe 103 and the pressurizing device 106 in the example of FIGS.

In the present invention, the ratio of the group III metal to nitrogen or a compound containing nitrogen is controlled to be constant, and
A group nitride crystal is grown.

FIG. 6 is a diagram (cross-sectional view) showing another configuration example of the crystal growth apparatus according to the present invention. In the example of FIG. 6, a case where the configuration of the crystal growth apparatus of FIG. 2 is used as a basic configuration is shown. However, it is of course possible to use the configuration of the crystal growth apparatus shown in FIG. 1 as a basic configuration.

In the crystal growth apparatus shown in FIG.
Is made of niobium, and a nickel film 117 is coated on an inner wall of a region where the metal gallium 104 of the metal supply tube 103 made of stainless steel contacts.

In the crystal growth apparatus shown in FIG. 1 or FIG. 2, the material of the growth vessel 102 is stainless steel, and the metal gallium directly contacts the inner wall of the metal supply pipe 103 made of stainless steel. The chromium contained in the stainless steel, which is the material of the tube 103, elutes and mixes into the raw materials and their products as the temperature rises.
In this crystal growth apparatus, the material of the growth vessel 102 is made of niobium, and the nickel film 11 is formed on the inner wall of the metal supply pipe 103.
No. 7 is coated, and niobium and nickel do not elute or mix into the raw materials and their products even when the temperature rises.

As described above, the crystal growth apparatus shown in FIG.
In the case of growing a group III nitride crystal, it is possible to grow a high-purity group III nitride crystal by preventing impurities from being mixed with a material used in a crystal growth apparatus.

In the above-described example, niobium is used for the growth container 102 and the nickel film 117 is coated on the metal supply pipe 103. However, the material of the growth container 102 and the coating material of the metal supply film 103 may be niobium or nickel. The material is not limited, and any material may be used as long as the region in contact with the raw material does not elute or mix with the raw material and their products.

In other words, it suffices that the region in contact with the raw material is covered with a material that does not elute or mix with the raw material and their products. That is, in the crystal growth apparatus shown in FIG. 1 or FIG. 2, the regions in contact with the raw material are a region where crystal growth is performed and a region where the raw material is supplied. What is necessary is just to be covered with the material which does not elute and mix with those products.

In the present invention, a group III nitride semiconductor device can be manufactured by using the group III nitride crystal grown by the above-described crystal growth method and crystal growth apparatus.

FIG. 7 is a diagram showing a configuration example of a semiconductor device according to the present invention. In the example of FIG. 7, the semiconductor device is configured as a semiconductor laser. Referring to FIG. 7, this semiconductor device has an n-type AlGaN cladding layer 702 and an n-type G layer on an n-type GaN substrate 701 using a group III nitride crystal grown in the manner described above.
aN guide layer 703, InGaN MQW (multiple quantum well) active layer 704, p-type GaN guide layer 705, p-type A
lGaN cladding layer 706, p-type GaN contact layer 7
07 are sequentially grown. As this crystal growth method, a thin film crystal growth method such as MOVPE (metal organic chemical vapor deposition) or MBE (molecular beam epitaxy) can be used.

Next, GaN, AlGaN, InGaN
A ridge structure is formed on the laminated films 701 to 707 of
An SiO ₂ insulating film 708 is formed in a state where only the contact region is perforated, and a p-side ohmic electrode Au / Ni 709 and an n-side ohmic electrode Al
/ Ti 710 is formed to form the semiconductor laser of FIG.

The p-side ohmic electrode A of this semiconductor laser
u / Ni709 and n-side ohmic electrode Al / Ti7
By injecting a current from 10, the semiconductor laser oscillates and can emit laser light in the direction of arrow A in FIG.

Since this semiconductor laser uses the group III nitride crystal (GaN crystal) of the present invention as the substrate 701, the semiconductor laser device has few defects, has a large output operation, and has a long life. . The GaN substrate 7
01 is an n-type, so that the electrode 71
0 can be formed, and it is not necessary to take out the two electrodes on the p-side and the n-side only from the surface as in the prior art shown in FIG. 9, so that the cost can be reduced. Further, the light emitting end face can be formed by cleavage, and a low-cost and high-quality device can be realized in addition to chip separation.

FIG. 8 is a diagram showing another configuration example of the semiconductor device according to the present invention. In the example of FIG. 8, the semiconductor device is configured as a field-effect transistor having a two-dimensional electron gas. Referring to FIG. 8, this semiconductor device is provided on a GaN substrate 801 using a group III nitride crystal grown in the manner described above.
1N insulating layer 802, GaN buffer layer 803, AlGa
N lower barrier layer 804, GaN channel layer 805, AlG
An aN barrier layer 806 and an n-GaN contact layer 807 are sequentially crystal-grown. As this crystal growth method, M
A thin film crystal growth method such as an OVPE (metal organic chemical vapor deposition) method or an MBE (molecular beam epitaxy) method can be used.

Next, element isolation is performed. In this element separation, although not shown in FIG. 8, at least the entire GaN channel layer 805 is etched, and the AlGaN lower barrier layer 804 is separated. The gate electrode 808 is in contact with the AlGaN upper barrier layer 806, and the Au / Ni
The structure is a Schottky junction. The source electrode 808 and the drain electrode 809 are in contact with the n-GaN contact layer 807, and have an ohmic junction due to the stacked structure of Al / Ti.

With such a device structure, the gate electrode 8
When a gate voltage is applied to the GaN channel layer 08, a two-dimensional electron gas is generated in the GaN channel layer 805. In this state, by applying a source / drain voltage between the source electrode 809 and the drain electrode 810, field-effect transistor characteristics can be obtained.

In the configuration example of FIG. 8, the GaN channel layer 80
5 has a double hetero structure in which upper and lower AlGaN barrier layers 806 and 804 are sandwiched.
A single hetero structure with only the N barrier layer 806 is also applicable. Further, although a GaN layer is used as the channel layer 805, for example, InGaN, AlInGaN, or the like can be used as long as the channel gap is smaller than that of the barrier layer. Further, n-Ga is used as the contact layer 807.
Although an N layer is used, the AlGaN barrier layer 806 has an n-A
A contact layer may also be used as lGaN.

Further, the present invention is applicable not only to the field effect transistor having the two-dimensional electron gas shown in FIG. 8, but also to a junction type field effect transistor and a heterobipolar transistor.

[0076]

As described above, according to the first to eleventh aspects of the present invention, the additional raw material is supplied after the crystal growth of the group III nitride is started. The crystal can be grown to a practical size large enough to produce a device.
Moreover, a group III nitride crystal (substrate) of a practical size,
It can be manufactured without going through complicated steps as in the first and second conventional techniques and without using an expensive reaction vessel which is a problem of the third conventional technique. Also,
Since this is not a thick-film crystal growth using a heterogeneous substrate as in the first and second prior arts, it is possible to greatly reduce crystal defects contained in the manufactured group III nitride crystal.

In particular, according to the invention of claim 8, III
Since the area where the pressure difference between the nitrogen pressure and the atmospheric pressure necessary for growing the group III nitride crystal is generated and the area where the temperature required for the group III nitride grows are separated, temperature control is performed. And pressure control can be performed reliably, and the cost of the reaction vessel can be reduced. That is,
An arbitrary pressure can be applied from the inside and outside of the reaction vessel to the region of the reaction vessel where the temperature at which the group III nitride crystal grows can be applied. Therefore, the material of the reaction vessel is made of a general material such as stainless steel. However, the thickness can be reduced, and a crystal growth apparatus can be realized at low cost.

According to the ninth aspect of the present invention, by introducing nitrogen between the outer vessel and the reaction vessel, it becomes possible to prevent the region where the crystal growth temperature of the reaction vessel is reached or the oxidation of the heater. In addition, the life of the crystal growth apparatus can be extended. As a result, further cost reduction can be realized.

According to the tenth aspect of the present invention, the region in contact with the raw material is covered with a material which does not elute or mix with the raw material and their products.
It becomes possible to prevent impurities from being mixed into the group I nitride crystal, and to provide a high-purity group III nitride crystal.

According to the eleventh aspect of the present invention, a group III nitride crystal is grown using the crystal growth method according to any one of the first to third aspects, thereby providing a semiconductor device. It is possible to provide, at low cost, a group III nitride crystal that is large enough to be able to be manufactured and has high crystal quality.

According to the twelfth aspect of the present invention, a high-performance device can be realized at low cost by manufacturing a semiconductor device using the group III nitride crystal according to the eleventh aspect. That is, as described above, the group III nitride crystal is a high-quality crystal with few crystal defects,
Fabricate devices using Group I nitrides or III
A high-performance device can be realized by manufacturing a device from the growth of a thin film using the substrate as a substrate for growing a thin film crystal of a group nitride.

According to the thirteenth aspect, by manufacturing an optical device using the group III nitride crystal according to the eleventh aspect, a high-performance optical device can be realized at low cost. The term “high performance” as used herein means, for example, a semiconductor laser or a light emitting diode which has a high output and a long life, which has not been realized conventionally, and a light receiving device which has a low noise and a long life.

According to the fourteenth aspect of the present invention, a high-performance electronic device can be realized at low cost by manufacturing an electronic device using the group III nitride crystal according to the eleventh aspect. The term "high performance" as used herein means, for example, low noise, high speed operation, and high temperature operation.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a crystal growth apparatus according to the present invention.

FIG. 2 is a diagram showing another configuration example of the crystal growth apparatus according to the present invention.

FIG. 3 is a diagram for explaining a crystal growth method of the present invention.

FIG. 4 is a view for explaining a crystal growth method of the present invention.

FIG. 5 is a graph showing the relationship between Ga / (Na + Ga) and the GaN composition, that is, Ga / N, using the nitrogen pressure a in the reaction vessel as a parameter.

FIG. 6 is a diagram showing another configuration example of the crystal growth apparatus according to the present invention.

FIG. 7 is a diagram showing a configuration example of a semiconductor device (optical device) according to the present invention.

FIG. 8 shows a semiconductor device (electronic device) according to the present invention.
FIG. 3 is a diagram showing a configuration example of the first embodiment.

FIG. 9 is a diagram showing a laser diode shown in the prior art.

[Explanation of symbols]

Reference Signs List 101 Reaction vessel 102 Growth vessel 103 Metal supply pipe 104 Group III metal 105 Hole 106 Pressurizing device 107 Internal space of reaction vessel 108 Nitrogen supply pipe 109 Pressure controller 110 Lower heater 111 Side heater 112 Outer vessel 113 Second nitrogen supply Tube 114 pressure control device 115 heat insulator 116 group III nitride crystal 117 nickel film 120 flux 121 group III metal 701 n-type GaN substrate 702 n-type AlGaN cladding layer 703 n-type GaN guide layer 704 InGaN MQW (multiple quantum well) active layer 705 p-type GaN guide layer 706 p-type AlGaN cladding layer 707 p-type GaN contact layer 708 SiO ₂ insulating film 709 p-side ohmic electrode 710 n-side ohmic electrode 801 GaN substrate 802 AlN insulating layer 803 GaN buffer § layer 804 AlGaN lower barrier layer 805 GaN channel layer 806 AlGaN barrier layer 807 n-GaN contact layer 808 gate electrode 808 source electrode 809 drain electrode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 33/00 H01L 33/00 C H01S 5/343 H01S 5/343

Claims (14)

[Claims] At least a group III metal and a flux are contained in a reaction vessel. Nitrogen or a compound containing nitrogen is introduced into the reaction vessel from outside the reaction vessel in order to grow a group III nitride crystal. Characterized by introducing
A method for growing a group III nitride crystal. 2. A reaction vessel containing at least a group III metal and a flux, wherein nitrogen or a compound containing nitrogen is introduced into the reaction vessel to grow a group III nitride crystal. At this time, in order to increase the size of the group III nitride crystal, during the growth of the group III nitride crystal, a group III nitride crystal is further supplemented with a group III metal. Growth method. 3. The crystal growth method according to claim 1, wherein the ratio of the group III metal to nitrogen or a compound containing nitrogen is controlled to be constant to grow the group III nitride crystal. Characteristic method for growing a group III nitride crystal. 4. A reaction vessel containing at least a group III metal and a flux, wherein nitrogen or a compound containing nitrogen is introduced into the reaction vessel from outside the reaction vessel in order to grow a group III nitride crystal. A crystal growth apparatus comprising a means for introducing. 5. A reaction vessel containing at least a group III metal and a flux, wherein nitrogen or a compound containing nitrogen is introduced into the reaction vessel to grow a group III nitride crystal. At this time, in order to increase the size of the group III nitride crystal, the crystal growth is characterized by further comprising a means for additionally supplying a group III metal during the crystal growth of the group III nitride crystal. apparatus. 6. The crystal growth apparatus according to claim 4, wherein a ratio of a group III metal to nitrogen or a compound containing nitrogen is controlled to be constant when growing a group III nitride crystal. A crystal growth apparatus comprising: 7. A crystal growth apparatus for growing a group III nitride crystal using at least a flux, a group III metal, and nitrogen or a compound containing nitrogen, comprising: A crystal growth apparatus, wherein a region where a group III nitride crystal is grown is separated from a region where a group III metal and nitrogen or a compound containing nitrogen are supplied. 8. The crystal growth apparatus according to claim 7, wherein
An outer container is further provided outside the reaction container, and II
It is characterized in that the region where the pressure difference between nitrogen pressure and atmospheric pressure necessary for growing Group I nitride crystal is generated and the region where the temperature required for growing Group III nitride is reached are separated. Crystal growth equipment. 9. The crystal growth apparatus according to claim 8, wherein
A crystal growth apparatus characterized in that nitrogen is introduced between an outer vessel and a reaction vessel. 10. The crystal growth apparatus according to claim 7, wherein the region in contact with the raw material is:
A crystal growth apparatus characterized by being covered with a material that does not elute or mix with the raw materials and their products. 11. A group III nitride crystal grown using the crystal growth method according to claim 1. Description: 12. A group III nitride semiconductor device manufactured using the group III nitride crystal according to claim 11. 13. The group III nitride semiconductor device according to claim 12, wherein the group III nitride semiconductor device is
A group III nitride semiconductor device, which is an optical device. 14. The group III nitride semiconductor device according to claim 12, wherein the group III nitride semiconductor device is
A group III nitride semiconductor device, which is an electronic device.