JP2008001593A - Crystal manufacturing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crystal manufacturing apparatus of depositing a group III nitride crystal to a practical size for use in optical devices and electronic devices such as high performance light-emission diodes and LD's. <P>SOLUTION: The apparatus is equipped with a reaction vessel 101 containing the raw material 104, a feed pipe 108 feeding a gas forming a crystal by reacting with the raw material 104 to the reaction vessel 101, heaters 110 and 111 disposed around the reaction vessel 101 and an outer vessel 112 covering the heaters 110 and 111 and the reaction vessel 101. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a crystal manufacturing apparatus for manufacturing a group III nitride crystal.

  Currently, most InGaAlN-based (Group III nitride) devices used as purple-blue-green light sources are MOCVD (metal organic chemical vapor deposition) or MBE (molecular beam) on sapphire or SiC substrates. The crystal growth method is used for crystal growth. When sapphire or SiC is used as a substrate, crystal defects due to large difference in thermal expansion coefficient and difference in lattice constant from group III nitride increase. For this reason, there is a problem that the device characteristics are poor, for example, it is difficult to extend the life of the light emitting device, or the operating power is increased.

  In addition, when applied to an electronic device, a high concentration of crystal defects serves as a leakage current path, leading to deterioration of characteristics. Further, the field effect transistor using a two-dimensional electron gas has 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, but this confinement effect is reduced when lattice relaxation due to defects occurs. As a result, the two-dimensional electron mobility is reduced and the transistor characteristics are deteriorated.

  Furthermore, in the case of a sapphire substrate, since it is insulative, it is impossible to take out the electrode from the substrate side as in the conventional light emitting device, and it is necessary to take out the electrode from the nitride semiconductor surface side where the crystal has grown. . As a result, there is a problem that the device area is increased, leading to high costs. In addition, a group III nitride semiconductor device fabricated on a sapphire substrate is difficult to be separated by cleaving, and it is not easy to cleave a resonator end face required for a laser diode (LD). For this reason, at present, resonator end faces are formed by dry etching, or resonator end faces are formed in a form close to cleavage after polishing the sapphire substrate to a thickness of 100 μm or less. Also in this case, it is impossible to easily separate the resonator end face and the chip as in a conventional LD in a single process, resulting in process complexity and cost.

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

For example, Non-Patent Document 1, “Japanese Journal of Applied Physics Vol.36 (1997) Part 2, No. 12A, L1568-1571” (hereinafter referred to as the first prior art), as shown in FIG. A laser diode (LD) is shown. 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 with a MOVPE (metal organic vapor phase epitaxy) apparatus, and then a SiO ₂ mask 4 for selective growth is formed. The 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, a GaN film 3 having a thickness of 20 μm is again grown on the SiO ₂ mask 4 by using a MOVPE apparatus, so that GaN is selectively grown in the lateral direction, compared with a case where selective lateral growth is not performed. This reduces crystal defects. Further, by introducing a modulation-doped strained superlattice layer (MD-SLS) 5 formed thereon, crystal defects are prevented from extending to the active layer 6. As a result, the device lifetime can be increased as compared to the case where the selective lateral growth and modulation-doped strained superlattice layer is not used.

In the case of this first prior art, it is possible to reduce crystal defects compared to the case where a GaN film is not selectively grown in the lateral direction on the sapphire substrate. The aforementioned problems with cleavage still remain. Furthermore, the crystal growth by the MOVPE apparatus is required twice with the SiO ₂ mask formation process in between, and a new problem arises that the process becomes complicated.

  As another method, for example, “Applied Physics Letters, Vol. 73, No. 6, P832-834 (1998)” (hereinafter referred to as the second prior art), which is Non-Patent Document 2, includes a GaN thickness. It has been proposed to apply a membrane substrate. In the second prior art, after the selective lateral growth of 20 μm of the first prior art described above, a 200 μm thick GaN thick film is grown by an H-VPE (hydride vapor phase epitaxy) apparatus, and then this thickness is increased. The grown GaN film is polished from the sapphire substrate side to a thickness of 150 μm to produce a GaN substrate. Using the MOVPE apparatus on this GaN substrate, crystal growth necessary for the LD device is sequentially performed to manufacture the LD device. As a result, in addition to the problem of crystal defects, it is possible to solve the above-described problems related to insulation and cleavage by using a sapphire substrate.

  However, the process of the second conventional technique is more complicated than that of the first conventional technique, which further increases the cost. In addition, when a GaN thick film having a thickness of 200 μm is grown by the second prior art method, the stress associated with the lattice constant difference and the thermal expansion coefficient difference from sapphire, which is the substrate, is increased, resulting in a new problem of cracking. Occurs. For this reason, it is difficult to increase the area, which leads to further cost increase.

  On the other hand, Non-Patent Document 3, “Journal of Crystal Growth, Vol.189 / 190, p.153-158 (1998)” (hereinafter referred to as third prior art), grows a bulk crystal of GaN. It has been proposed to use it as a homoepitaxial substrate. This technique is a technique for crystal growth of GaN from liquid Ga at a high temperature of 1400 to 1700 ° C. and a nitrogen pressure of several tens of kbar. In this case, a group III nitride semiconductor film necessary for the device can be grown using the bulk-grown GaN substrate. Therefore, a GaN substrate can be provided without complicating the process as in the first and second conventional techniques.

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

As a technique for solving this problem of GaN crystal growth at high temperature and high pressure, Non-Patent Document 4, “Chemistry of Materials Vol.9 (1997) p.413-416” (hereinafter referred to as the fourth conventional technique). GaN crystal growth method using Na as a flux has been proposed. In this method, sodium azide (NaN ₃ ) as a flux and metal Ga are used as raw materials, and sealed in a stainless steel reaction vessel (inner dimensions; inner diameter = 7.5 mm, length = 100 mm) in a nitrogen atmosphere, By holding the reaction vessel at a temperature of 600 to 800 ° C. for 24 to 100 hours, a GaN crystal is grown. In the case of the fourth prior art, crystal growth at a relatively low temperature of about 600 to 800 ° C. is possible, and the pressure in the container is about 100 kg / cm ² at most, which is higher than that of the third prior art. It is a feature that can be lowered. However, the problem with this method is that the crystal size obtained is small enough to be less than 1 mm. This size is too small for practical use of the device, as in the case of the third prior art.
Japanese Journal of Applied Physics Vol.36 (1997) Part 2, No.12A, L1568-1571 Applied Physics Letters, Vol.73, No.6, P832-834 (1998) Journal of Crystal Growth, Vol.189 / 190, p.153-158 (1998) Chemistry of Materials Vol.9 (1997) p.413-416

  The present invention does not complicate the process that is the problem of the first and second prior arts, without using the expensive reaction vessel that is the problem of the third prior art, and the third and fourth. The growth of III-nitride crystals of practical size for producing high-performance light-emitting diodes, LDs, and other optical and electronic devices without reducing the size of crystals, which is a problem with conventional technologies An object of the present invention is to provide a crystal manufacturing apparatus that can be used.

  The crystal production apparatus of the present invention includes a reaction vessel containing a raw material, a supply pipe that supplies the reaction vessel with a gas that reacts with the raw material to form crystals, a heater for heating provided around the reaction vessel, And an outer container covering the heater and the reaction container.

  In addition, the present invention can be configured to further include a pressure control device that reduces a pressure difference between a pressure in a region between the outer container and the reaction container and a pressure in the reaction container.

  Moreover, this invention can be comprised so that the heat insulating material which covers the said heater for heating may be further provided in the area | region between the said outer side container and the said reaction container.

  In addition, the present invention can be configured to further include a gas supply pipe that supplies gas to a region between the outer container and the reaction container.

  The gas that reacts with the raw material to form a crystal can be composed of the same gas as the gas supplied to the region between the outer container and the reaction container, and further reacts with the raw material to form a crystal. Nitrogen gas can be used as the gas to be generated.

  Moreover, this invention can be comprised so that it may be further equipped with the growth container arrange | positioned inside the said reaction container and hold | maintaining the said raw material.

  Moreover, the area | region which touches the said raw material can be comprised with the material which does not elute to the said raw material.

  According to the present invention, since the additional raw material is supplied after the group III nitride crystal growth starts, it is greatly increased to a practical size enough to produce a device using the group III nitride crystal. It becomes possible to grow. In addition, the III-nitride crystal (substrate) having a practical size is expensive without being subjected to complicated processes as in the first and second prior arts, and is a problem of the third prior art. It can be produced without using a reaction vessel. Further, since it is not thick film crystal growth using a heterogeneous substrate as in the first and second prior arts, crystal defects contained in the manufactured group III nitride crystal can be greatly reduced.

  In particular, the present invention separates the region where the pressure difference between the nitrogen pressure and the atmospheric pressure necessary for the growth of the group III nitride crystal and the temperature required for the growth of the group III nitride are separated. Therefore, temperature control and pressure control can be reliably performed, and the cost of the reaction vessel can be suppressed. 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 of group III nitride becomes crystal growth. Therefore, the reaction vessel is generally made of stainless steel or the like. Even with a simple material, the thickness can be reduced, and a crystal growth apparatus can be realized at low cost.

  Further, by introducing nitrogen between the outer vessel and the reaction vessel, it becomes possible to prevent the region of the reaction vessel where the crystal growth temperature is reached and the oxidation of the heater, thereby extending the life of the crystal growth apparatus. As a result, further cost reduction can be realized.

  In addition, since the region in contact with the raw material is covered with a material that does not elute or mix into the raw material and their products, it is possible to suppress the contamination of impurities into the finally obtained group III nitride crystal. It becomes possible to provide a pure group III nitride crystal.

  In addition, Group III nitride crystals that are large enough to produce semiconductor devices and have high crystal quality can be provided at low cost by growing Group III nitride crystals using the manufacturing apparatus of the present invention. It becomes possible to do.

  In addition, a high-performance device can be realized at low cost by manufacturing a semiconductor device using a group III nitride crystal manufactured using the manufacturing apparatus of the present invention. In other words, as described above, this group III nitride crystal is a high-quality crystal with few crystal defects, and a device is manufactured using this group III nitride, or a thin film crystal growth of group III nitride is performed. A high-performance device can be realized by manufacturing a device from a thin film growth using it as a substrate.

  Moreover, a high-performance optical device can be realized at low cost by manufacturing an optical device using a group III nitride crystal manufactured by using the manufacturing apparatus of the present invention. The high performance referred to here is, for example, a high output and long life that cannot be realized in the case of semiconductor lasers and light emitting diodes, and a light receiving device has low noise and long life.

  Moreover, a high-performance electronic device can be realized at low cost by producing an electronic device using a group III nitride crystal manufactured using the manufacturing apparatus of the present invention. The high performance mentioned here means that, for example, low noise, high speed operation, and high temperature operation are possible.

  Hereinafter, embodiments of the present invention will be described 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 is provided with a growth vessel 102 for carrying out crystal growth in a closed reaction vessel 101 made of stainless steel.

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

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

  The locations where the metal supply pipe 103 and the nitrogen supply pipe 108 are in contact with the reaction vessel 101 are spatially blocked from the outside by welding, metal sealing, 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 crystal growth of a group III nitride crystal, at least a flux (for example, metal Na or a compound containing Na (such as sodium azide)) and a group III metal (for example, Ga (gallium)) And is housed. The metal supply pipe 103 has 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. The upper end of the side opposite to the hole 105 of 103 is located outside the reaction vessel 101 and is equipped with a pressurizing device 106 that can apply pressure with a predetermined gas (for example, nitrogen gas or inert gas). Yes. That is, the metal supply pipe 103, the hole 105, and the growth vessel 102 are controlled at the lowest end by controlling the pressure with a high-pressure gas (for example, nitrogen gas or inert gas) by the pressurizing device 106 at the upper end of the metal supply pipe 103. The group III metal (eg, Ga (gallium)) 104 can be dropped from the hole 105 into the growth vessel 102.

  1 includes the temperature of the growth vessel 102 in the reaction vessel 101 and the temperature of the region where the group III metal (for example, Ga (gallium)) 104 of the metal supply pipe 103 is stored. The heating means (110, 111) is provided so that the temperature can be controlled to an arbitrary temperature. Here, the heating means (110, 111) includes a lower heater 110 located at the lower part outside the reaction vessel 101 and a side heater 111 located outside the side wall of the reaction vessel 101. These heaters 110 and 111 store the temperature of the growth vessel 102 in the reaction vessel 101 and the group III metal (for example, Ga (gallium)) 104 in the metal supply pipe 103 by a temperature control mechanism (not shown). It is possible to control the temperature of the area being set to an arbitrary temperature.

  1 uses at least a flux (for example, metal Na or a compound containing Na), a group III metal (for example, Ga (gallium)), and nitrogen or a compound containing nitrogen to form a group III nitride crystal. A region (102) in which crystal growth of a group III nitride crystal (for example, GaN crystal) is performed in a reaction vessel 101 in which temperature and pressure are controlled, and a group III metal (for example, The regions (103, 108) to which Ga (gallium)) and nitrogen (N) or a compound containing nitrogen (N) are supplied are separated. The reaction vessel 101 includes a mechanism (110, 111) that can control a region including at least a region (102) where crystal growth is performed to an arbitrary temperature. Furthermore, the mechanism (108,109) which can control the inside of the reaction container 101 to arbitrary nitrogen pressure is also provided.

  FIG. 2 is a diagram (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.

  The crystal growth apparatus of FIG. 2 is basically the same as the crystal growth apparatus of FIG. That is, referring to FIG. 2, this crystal growth apparatus is also provided with a growth vessel 102 for crystal growth in a closed reaction vessel 101 made of stainless steel, like the crystal growth device of FIG. Yes.

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

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

  The locations where the metal supply pipe 103 and the nitrogen supply pipe 108 are in contact with the reaction vessel 101 are spatially blocked from the outside by welding, metal sealing, 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 least the flux (for example, metal Na or a compound containing Na (such as sodium azide)) and the group III metal (for example, Ga (gallium)) at the start of the group III nitride crystal growth. And is housed. The metal supply pipe 103 has 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. The upper end of the side opposite to the hole 105 of 103 is located outside the reaction vessel 101 and is equipped with a pressurizing device 106 that can apply pressure with a predetermined gas (for example, nitrogen gas or inert gas). Yes. That is, the metal supply pipe 103, the hole 105, and the growth vessel 102 are controlled at the lowest end by controlling the pressure with a high-pressure gas (for example, nitrogen gas or inert gas) by the pressurizing device 106 at the upper end of the metal supply pipe 103. The group III metal (eg, Ga (gallium)) 104 can be dropped from the hole 105 into the growth vessel 102.

  Also in the crystal growth apparatus of FIG. 2, the temperature of the growth vessel 102 in the reaction vessel 101 and the temperature of the region where the group III metal (for example, Ga (gallium)) 104 of the metal supply pipe 103 is stored. The heating means (110, 111) is provided so that can be controlled to an arbitrary temperature. Here, the heating means (110, 111) includes a lower heater 110 located at the lower part outside the reaction vessel 101 and a side heater 111 located outside the side wall of the reaction vessel 101. These heaters 110 and 111 store the temperature of the growth vessel 102 in the reaction vessel 101 and the group III metal (for example, Ga (gallium)) 104 in the metal supply pipe 103 by a temperature control mechanism (not shown). It is possible to control the temperature of the area being set to an arbitrary temperature.

  As described above, the crystal growth apparatus of FIG. 2 also has at least a flux (for example, metal Na or a compound containing Na), a group III metal (for example, Ga (gallium)) and nitrogen or the same as the crystal growth apparatus of FIG. A group III nitride crystal is grown using a compound containing nitrogen, and a group III nitride crystal (for example, a GaN crystal) is grown in a reaction vessel 101 in which temperature and pressure are controlled. A region (102) to be formed is separated from a region (103, 108) to which a Group III metal (for example, Ga (gallium)) and nitrogen (N) or a compound containing nitrogen (N) are supplied. The reaction vessel 101 includes a mechanism (110, 111) that can control a region including at least a region (102) where crystal growth is performed to an arbitrary temperature. Furthermore, the mechanism (108,109) which can control the inside of the reaction container 101 to arbitrary nitrogen pressure is also provided.

  By the way, in the crystal growth apparatus of FIG. 2, an outer container 112 is further provided so as to cover the reaction container 101, the lower heater 110, and the side heater 111, and between the outer container 112, the lower heater 110, and the side heater 111. Is provided with a heat insulating material 115.

  Further, both the metal supply pipe 103 and the nitrogen supply pipe 108 penetrate the outer container 112 and reach the reaction container 101.

  Furthermore, in the crystal growth apparatus of FIG. 2, it is possible to apply an arbitrary gas pressure (for example, nitrogen pressure) to the region between the outer vessel 112 including the heaters 110 and 111 and the heat insulating material 115 and the reaction vessel 101. As shown, a second gas supply pipe (for example, a nitrogen supply pipe) 113 and a pressure control device 114 are installed. That is, the second gas supply pipe 113 is installed so as to penetrate between the outer container 112 and the reaction container 101 from the outside of the outer container 112.

  In the crystal growth apparatus having the configuration shown in FIG. 2, an outer vessel 112 is provided outside the reaction vessel 101, and the outer vessel 112 has a gas having a pressure necessary to reduce the pressure difference from the nitrogen pressure in the reaction vessel 101. (For example, nitrogen) is introduced, the pressure difference between the inside and outside of the reaction vessel 101 can be made significantly smaller than the pressure difference between the nitrogen pressure and the atmospheric pressure necessary for the growth of the group III nitride crystal. It becomes possible. Thereby, pressure resistance is not requested | required of the reaction container 101, and the reaction container 101 should just have only heat resistance. On the other hand, the outer container 112 is not required to have high heat resistance because the heat insulating material 115 is provided between the outer container 112, the lower heater 110, and the side heater 111, and the group III nitride crystal is not required. It is only necessary to have a pressure resistance that can withstand a differential pressure between a pressure comparable to the nitrogen pressure necessary for the growth of the gas and the atmospheric pressure. 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 device configuration of FIG. 2, the heat resistance and pressure resistance are outside the reaction vessel 101. It can be dispersed in the container 112.

  As described above, in the crystal growth apparatus shown in FIG. 2, the region (outer vessel 112) where the pressure difference between the nitrogen pressure and the atmospheric pressure necessary for the growth of the group III nitride crystal occurs and the group III nitride grows. The temperature control and pressure control can be reliably performed by separating the region (reaction vessel 101) where the temperature necessary for the operation is separated.

  That is, in the crystal growth apparatus having the configuration shown in FIG. 2, since the heat insulating material 115 is provided between the outer vessel 112, the lower heater 110, and the side heater 111, the temperature of the lower heater 110 and the side heater 111 is increased. Control can be performed more reliably. In the crystal growth apparatus having the configuration shown in FIG. 2, an arbitrary gas pressure (for example, nitrogen gas pressure) is applied to a region between the outer vessel 112 including the heaters 110 and 111 and the heat insulating material 115 and the reaction vessel 101. Since the second gas supply pipe (nitrogen supply pipe) 113 and the pressure control device 114 are installed, the nitrogen pressure control inside the reaction vessel 101 can be more reliably performed.

  In the crystal growth apparatus of FIG. 2, the region (outer vessel 112) where the pressure difference between the nitrogen pressure and the atmospheric pressure necessary for the growth of the group III nitride crystal occurs and the group III nitride grow. Since the region (reaction vessel 101) where the temperature is required for the separation is separated, the cost of the reaction vessel can be reduced. 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 of group III nitride becomes crystal growth. Therefore, the reaction vessel is generally made of stainless steel or the like. 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 of FIG. 1 or 2 will be described. The raw material for crystal growth of the group III nitride crystal (for example, GaN crystal) is at least a flux (for example, metal Na or a compound containing Na), a group III metal (for example, metal gallium), nitrogen or a compound containing nitrogen. is there.

  In the crystal growth apparatus of FIG. 1 or FIG. 2, a growth vessel 102 is installed in a reaction vessel 101. Initially, in the growth vessel 102, as shown in FIG. , Sodium azide and sodium metal) 120 and group III metal (eg, metal gallium) 121. In this state, nitrogen or a compound containing nitrogen is introduced into the reaction vessel 101 from the nitrogen supply pipe 108, and the inside of the reaction vessel 101 is brought 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), as shown in FIG. 4, the group III nitride crystal (for example, The growth of (GaN) 116 is started.

  At this time, the amount of nitrogen in the reaction vessel 101 decreases as the growth of the group III nitride crystal 116 proceeds, and the nitrogen pressure in the reaction vessel 101 decreases. Therefore, the decrease in the nitrogen pressure in the reaction vessel 101 is reduced. Therefore, nitrogen or a compound containing nitrogen is introduced into the reaction vessel 101 from the nitrogen supply pipe 108 by the pressure control device 109 during the crystal growth so that the nitrogen pressure in the reaction vessel 101 is always substantially constant. That is, the nitrogen pressure in the reaction vessel 101 is controlled by adding an additional raw material with nitrogen or a compound containing nitrogen in an arbitrary amount from the nitrogen supply pipe 108. As a result, the nitrogen pressure in the reaction vessel 101 can be maintained at a substantially constant level, and the group III nitride crystal 116 can be continuously grown. Further, a group III metal (for example, metal gallium) is additionally supplied in an arbitrary amount from the metal supply pipe 103 into the reaction vessel 101. Thereby, a group III nitride crystal (for example, GaN crystal) can be grown greatly.

  FIG. 5 is a diagram showing the relationship of GaN composition to Ga / (Na + Ga), that is, Ga / N, using the nitrogen pressure a in the reaction vessel 101 as a parameter. From FIG. 5, in order to obtain a high-quality and large GaN crystal, it is necessary to continuously control the Ga amount and the nitrogen pressure in the reaction vessel 101 so that Ga / N is always “1”. . That is, in the present invention, the group III nitride crystal is grown by controlling the ratio of the group III metal and nitrogen or a compound containing nitrogen to be constant.

  More specifically, for example, a method of growing a group III nitride crystal using the crystal growth apparatus of FIG. 2 will be described. In the growth vessel 102 installed in the reaction vessel 101, flux (for example, sodium azide or metallic sodium) and a group III metal (metallic gallium) are initially placed as some raw materials. In addition, a group III metal (metal gallium) 104 is placed inside a metal supply pipe 103 for supplying a group III metal, and a metal supply pipe is formed by a pressurizing device 106 at the upper end of the metal supply pipe 103. The inside of 103 is pressurized so that metal gallium 104 can be supplied. Further, nitrogen can be pressurized and supplied into the reaction vessel 101 through a nitrogen supply pipe 108 and a pressure control device 109. In the crystal growth apparatus of FIG. 2, the region between the outer vessel 112 and the reaction vessel 101 is further pressurized by a second gas supply pipe (for example, a nitrogen supply pipe) 113 and a pressure control device 114. At this time, the gas pressures in the three regions of the reaction vessel 101, the region between the outer vessel 112 and the reaction vessel 101, and the metal supply pipe 103 by the pressurization device 106 are controlled to be substantially the same pressure. Has been.

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

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

  Thus, in the present invention, at least a group III metal and a flux are accommodated in the reaction vessel 101, and nitrogen is introduced into the reaction vessel 101 from the outside of the reaction vessel 101 in order to grow a group III nitride crystal. Alternatively, a compound containing nitrogen is introduced. Even if nitrogen or a compound containing nitrogen is introduced into the reaction vessel 101 from the outside of the reaction vessel 101, even if the growth of the group III nitride crystal proceeds and the amount of nitrogen in the reaction vessel 101 decreases, the reaction vessel 101 It becomes possible to control the amount of nitrogen in the inside constantly. 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 and a pressure control device 109 in the examples of FIGS.

  Further, in the present invention, at least a group III metal and a flux are accommodated in the reaction vessel 101, and nitrogen or a compound containing nitrogen is introduced into the reaction vessel 101 to grow a group III nitride crystal. At this time, in order to increase the size of the group III nitride crystal, a group III metal is additionally supplied during the growth of the group III nitride crystal. When the group III nitride crystal is grown, the size of the group III nitride crystal can be increased by additionally supplying a group III metal. The means for additionally supplying the group III metal is the metal supply pipe 103 and the pressurizing device 106 in the examples of FIGS.

  In the present invention, the ratio of the group III metal and nitrogen or a compound containing nitrogen is controlled to be constant, and the group III 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, as a basic configuration, it is of course possible to use the configuration of the crystal growth apparatus of FIG.

  In the crystal growth apparatus of FIG. 6, the material of the growth vessel 102 is niobium, and the inner wall of the region where the metal gallium 104 of the metal supply tube 103 made of stainless steel contacts is covered with a nickel film 117.

  In the crystal growth apparatus of FIG. 1 or FIG. 2, the growth vessel 102 is made of stainless steel, and metal gallium directly contacts the inner wall of the metal supply tube 103 made of stainless steel. As the temperature rises, chromium contained in the stainless steel, which is the material, elutes and mixes in the raw materials and their products. In the crystal growth apparatus of FIG. 3, the growth vessel 102 is made of niobium, and the metal supply pipe 103 A nickel film 117 is coated on the inner wall, and niobium and nickel are not eluted or mixed into the raw materials and their products even when the temperature rises.

  As described above, when the group III nitride crystal is grown by the crystal growth apparatus of FIG. 6, high-purity group III nitride crystal is prevented by preventing mixing of impurities from the material used in the crystal growth apparatus. It becomes possible to grow.

  In the above example, niobium is used for the growth vessel 102 and a nickel film 117 is coated on the metal supply pipe 103. However, the material of the growth vessel 102 and the coating material of the metal supply film 103 are not limited to niobium or nickel. As long as the region in contact with the raw material is a material that does not elute and mix into the raw materials and their products.

  In other words, the region in contact with the raw material only needs to be covered with a material that does not elute or enter into the raw material and their products. That is, in the crystal growth apparatus of FIG. 1 or FIG. 2, the region in contact with the raw material is a region where the crystal growth is performed and a region where the raw material is supplied. It suffices if the product is covered with a material that does not elute or enter.

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

  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, in this semiconductor device, an n-type AlGaN cladding layer 702 and an n-type GaN guide layer 703 are formed on an n-type GaN substrate 701 using a group III nitride crystal grown in the manner described above. , InGaN MQW (multiple quantum well) active layer 704, p-type GaN guide layer 705, p-type AlGaN cladding layer 706, and p-type GaN contact layer 707 are sequentially grown. As this crystal growth method, a thin film crystal growth method such as MOVPE (metal organic chemical vapor deposition) method or MBE (molecular beam epitaxy) method can be used.

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

  By injecting current from the p-side ohmic electrode Au / Ni 709 and the n-side ohmic electrode Al / Ti 710 of this semiconductor laser, this semiconductor laser oscillates and can emit laser light in the direction of arrow A in FIG. .

  Since this group III nitride crystal (GaN crystal) of the present invention is used as the substrate 701, this semiconductor laser has few defects in the semiconductor laser device, has a large output operation and a long life. Further, since the GaN substrate 701 is n-type, the electrode 710 can be formed directly on the substrate 701, and the two electrodes on the p-side and n-side are taken out only from the surface as in the prior art shown in FIG. This is not necessary, and the cost can be reduced. Further, the light emitting end face can be formed by cleaving, and in combination with chip separation, a low-cost and high-quality device can be realized.

  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, in this semiconductor device, an AlN insulating layer 802, a GaN buffer layer 803, and an AlGaN lower barrier layer 804 are formed on a GaN substrate 801 using a group III nitride crystal grown in the manner described above. , A GaN channel layer 805, an AlGaN barrier layer 806, and an n-GaN contact layer 807 are sequentially grown. As this crystal growth method, a thin film crystal growth method such as MOVPE (metal organic chemical vapor deposition) method or MBE (molecular beam epitaxy) method can be used.

  Next, element isolation is performed. In this element isolation, although not shown in FIG. 8, at least the GaN channel layer 805 is etched at least to the AlGaN lower barrier layer 804. The gate electrode 808 is in contact with the AlGaN upper barrier layer 806 and forms a Schottky junction due to the stacked structure of Au / Ni. 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 an Al / Ti laminated structure.

  With such a device structure, a two-dimensional electron gas is generated in the GaN channel layer 805 by applying a gate voltage to the gate electrode 808. 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.

  8 has a double hetero structure in which the GaN channel layer 805 is sandwiched between the upper and lower AlGaN barrier layers 806 and 804, but a single hetero structure having only the upper AlGaN barrier layer 806 is also applicable. is there. In addition, although a GaN layer is used as the channel layer 805, InGaN, AlInGaN, or the like can be applied as long as the band gap is smaller than that of the barrier layer. Further, although the n-GaN layer is used as the contact layer 807, the contact layer may also be used with the AlGaN barrier layer 806 as n-AlGaN.

  Furthermore, the present invention can be applied not only to the field effect transistor having the two-dimensional electron gas of FIG. 8, but also to a junction type field effect transistor and a heterobipolar transistor.

It is a figure which shows the structural example of the crystal growth apparatus which concerns on this invention. It is a figure which shows the other structural example of the crystal growth apparatus which concerns on this invention. It is a figure for demonstrating the crystal growth method of this invention. It is a figure for demonstrating the crystal growth method of this invention. It is the figure which showed the GaN composition with respect to Ga / (Na + Ga), ie, the relationship of Ga / N, using the nitrogen pressure a in a reaction container as a parameter. It is a figure which shows the other structural example of the crystal growth apparatus which concerns on this invention. It is a figure which shows the structural example of the semiconductor device (optical device) which concerns on this invention. It is a figure which shows the structural example of the semiconductor device (electronic device) which concerns on this invention. It is a figure which shows the laser diode shown by the prior art.

Explanation of symbols

101 Reaction vessel 102 Growth vessel 103 Metal supply tube 104 Group III metal 105 Hole 106 Pressurization device 107 Internal space 108 of reaction vessel Nitrogen supply tube 109 Pressure control device 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

Claims (8)

  A reaction vessel containing a raw material; a supply pipe that supplies a gas that reacts with the raw material to form crystals; to the reaction vessel; a heater provided around the reaction vessel; the heating heater and the reaction A crystal manufacturing apparatus comprising an outer container covering the container.   The crystal manufacturing apparatus according to claim 1, further comprising a pressure control device that reduces a pressure difference between a pressure in a region between the outer container and the reaction container and a pressure in the reaction container.   The crystal manufacturing apparatus according to claim 1, further comprising a heat insulating material that covers the heater for heating in a region between the outer container and the reaction container.   The crystal manufacturing apparatus according to any one of claims 1 to 3, further comprising a gas supply pipe that supplies a gas to a region between the outer container and the reaction container.   The crystal manufacturing apparatus according to claim 4, wherein a gas that reacts with the raw material to form a crystal is made of the same gas as a gas supplied to a region between the outer container and the reaction container.   The crystal manufacturing apparatus according to claim 5, wherein the gas that reacts with the raw material to form crystals is nitrogen gas.   The crystal manufacturing apparatus according to any one of claims 1 to 6, further comprising a growth vessel that is disposed inside the reaction vessel and holds the raw material.   The crystal manufacturing apparatus according to claim 1, wherein the region in contact with the raw material is made of a material that does not elute into the raw material.

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