JP2005206409A - Method for growing group iii nitride crystal, group iii nitride crystal, semiconductor device, and system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for growing a group III nitride crystal, by which a high quality group III nitride crystal having a practical large size and large area can be manufactured at a lower cost compared with the conventional ones. <P>SOLUTION: In the method for growing the group III nitride crystal from a melt 25 in which at least an alkali metal, a metal of group III and nitrogen are dissolved, the group III nitride crystal 30 is grown by incorporating a substance (e.g., lithium) for increasing the growth speed in the direction perpendicular to the c-axis of the group III nitride crystal higher than that in the c-axis direction into the melt 25. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

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

  At present, most of InGaAlN-based (group III nitride) devices used as ultraviolet, purple-blue-green light sources are formed on a sapphire or SiC substrate by MO-CVD (metal organic chemical vapor deposition), It is produced by crystal growth using the MBE method (molecular beam crystal growth method) or the like. Problems when using sapphire or SiC as a substrate include increased crystal defects due to large differences in thermal expansion coefficients and lattice constants from group III nitrides. Are bad (for example, it is difficult to extend the lifetime of the light-emitting device) or the operating power increases.

  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 becomes large, leading to high costs. In addition, a group III nitride semiconductor device fabricated on a sapphire substrate is difficult to be separated by cleavage, and it is not easy to obtain a resonator end face required for a laser diode (LD) by cleavage. 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 from the conventional LD and the chip in a single process, resulting in a complicated process and an increase in cost.

  In order to solve these problems, it has been proposed to reduce crystal defects by performing selective lateral growth of the group III nitride semiconductor film on the sapphire substrate and other devices. Although this method makes it possible to reduce crystal defects compared to the case where a GaN film is not selectively grown in a lateral direction on a sapphire substrate, the above-mentioned problems related to insulation and cleavage by using a sapphire substrate Still remains. Furthermore, the process is complicated, and problems of warping of the substrate due to the combination of different materials such as a sapphire substrate and a GaN thin film arise, which leads to higher costs.

  In order to solve these problems, it is most desirable to realize a GaN substrate that is the same as the material for crystal growth on the substrate. Therefore, research on crystal growth of bulk GaN has been made by vapor phase growth, melt growth and the like. However, a high-quality and practical size GaN substrate has not yet been realized.

As one method for realizing a GaN substrate, Non-Patent Document 1 (first prior art) proposes a GaN crystal growth method using Na as a flux. In this method, sodium azide (NaN ₃ ) and metal Ga are used as raw materials, and sealed in a stainless steel reaction vessel (inner vessel dimensions; inner diameter = 7.5 mm, length = 100 mm) in a nitrogen atmosphere. A GaN crystal is grown by holding at a temperature of 600 to 800 ° C. for 24 to 100 hours.

This first prior art is capable of crystal growth at a relatively low temperature of 600 to 800 ° C., and the pressure in the vessel is relatively low at about 100 kg / cm ^2, which is a practical growth condition. Is a feature. However, the problem with this method is that the crystal size obtained is small enough to be less than 1 mm.

  That is, in the first prior art, the reaction vessel is a completely closed system, and the raw material cannot be replenished from the outside. Therefore, the raw material is depleted during the crystal growth and the crystal growth stops, so that the size of the obtained crystal is as small as about 1 mm. This size is too small for practical use of the device.

  In order to solve the problem of the first prior art, methods as shown in Patent Document 1 and Patent Document 2 have been proposed.

  That is, Patent Document 1 (second prior art) shows a method of additionally supplementing a Group III metal during the growth of a Group III nitride crystal in order to increase the size of the Group III nitride crystal. ing. More specifically, in this method, as shown in FIG. 14, a growth vessel 102 and a group III metal supply tube 103 are provided in a reaction vessel 101, and pressure is applied to the group III metal supply tube 103 from the outside to accommodate the flux. The group III metal 104 is additionally supplied to the reaction vessel 102 formed.

Further, in Patent Document 2 (third prior art), the flux is accommodated by applying pressure from the outside to the melt supply pipe in which the mixed melt of flux (Na) and group III metal (Ga) is accommodated. A method of additionally replenishing the mixed melt to the growth vessel, and placing an intermetallic compound of flux (Na) and group III metal (Ga) in the growth vessel, and partially melting it to replenish the group III metal. The method is shown.
Chemistry of Materials Vol. 9 (1997) 413-416 JP 2001-058900 A JP 2001-102316 A

  In the second and third prior arts described above, additional replenishment of the raw material is performed during crystal growth, so that a large group III nitride crystal can be produced.

  However, there is a demand for a person skilled in the art to manufacture a practical large-sized, large-area group III nitride substrate crystal at a lower cost than the second and third prior arts.

  INDUSTRIAL APPLICABILITY The present invention is a group III nitride crystal growth method and a group III nitride capable of producing a large-sized, large-area, high-quality group III nitride crystal having a practical size at a lower cost than before. It is an object to provide crystal and semiconductor devices and systems.

  To achieve the above object, the invention described in claim 1 is a crystal growth method for growing a group III nitride crystal from a melt in which at least an alkali metal, a group III metal, and nitrogen are dissolved. It is characterized by containing a substance that controls the ratio of the growth rate in the c-axis direction of the group nitride crystal to the growth rate in the direction perpendicular to the c-axis.

  The invention according to claim 2 is the crystal growth method according to claim 1, wherein the growth rate of the group III nitride crystal in the direction perpendicular to the c-axis is higher than the growth rate in the c-axis direction. It is characterized in that a group III nitride crystal is grown by including the material to be treated.

  The invention according to claim 3 is the crystal growth method according to claim 1 or 2, wherein a seed crystal (for example, a plate-shaped seed crystal) is used, and a seed crystal (for example, a plate-shaped seed crystal) is used. A group III nitride crystal is grown on the main surface of the seed crystal (for example, a plate-shaped seed crystal) at a growth rate in the direction parallel to the main surface that is faster than the growth rate in the direction perpendicular to the main surface of the seed crystal. It is characterized by letting.

  The invention described in claim 4 is the crystal growth method according to claim 3, wherein a group III nitride crystal having a c-plane as a main surface (for example, a plate-like group III nitride crystal) is used as a seed crystal. A group III nitride crystal is grown on the c-plane of the seed crystal.

  The invention according to claim 5 is a crystal growth method for growing a group III nitride crystal from a melt in which at least an alkali metal, a group III metal, and nitrogen are dissolved, and lithium (Li) is included in the melt. It is characterized by that.

  A sixth aspect of the present invention is a group III nitride crystal grown by the crystal growth method according to any one of the first to fifth aspects.

  The invention described in claim 7 is a semiconductor device using the group III nitride crystal described in claim 6.

  The invention according to claim 8 is the semiconductor device according to claim 7, wherein the semiconductor device is a light emitting element having a semiconductor multilayer structure laminated on the group III nitride crystal according to claim 6. It is said.

  The invention according to claim 9 is the semiconductor device according to claim 7, wherein the semiconductor device is a light receiving element formed using the group III nitride crystal according to claim 6.

  According to a tenth aspect of the present invention, there is provided the semiconductor device according to the seventh aspect, wherein the semiconductor device is an electronic device formed using the group III nitride crystal according to the sixth aspect.

  An eleventh aspect of the invention is a system including the semiconductor device according to any one of the seventh to tenth aspects.

  According to the first aspect of the present invention, in the crystal growth method of growing a group III nitride crystal from a melt in which at least an alkali metal, a group III metal, and nitrogen are dissolved, the melt includes c of the group III nitride crystal. Since the substance for controlling the ratio between the growth rate in the axial direction and the growth rate in the direction perpendicular to the c-axis is included, the morphology of the crystal can be controlled.

  According to a second aspect of the present invention, in the crystal growth method according to the first aspect, in the melt, a growth rate in the direction perpendicular to the c-axis of the group III nitride crystal is determined from a growth rate in the c-axis direction. In addition, since the group III nitride crystal is grown by including a material that accelerates the crystal, the form of the crystal can be controlled in a plate shape. And since it can control to plate shape, it can use as it is as a board | substrate and the cost reduction of board | substrate manufacture is attained.

  According to a third aspect of the invention, in the crystal growth method of the first or second aspect, a seed crystal (for example, a plate-shaped seed crystal) is used, and a seed crystal (for example, a plate-shaped seed crystal) is used. The group III nitride crystal is formed on the main surface of the seed crystal (for example, a plate-like seed crystal) at a growth rate in a direction parallel to the main surface of Therefore, a crystal having a flat surface as a main surface can be grown.

  According to the invention of claim 4, in the crystal growth method of claim 3, the group III nitride crystal (plate-like group III nitride crystal) having the c-plane as the main surface is used as a seed crystal. Since the group III nitride crystal is grown on the c-plane of the seed crystal, a high-quality group III nitride crystal having a flat c-plane as the main surface can be grown.

  According to a fifth aspect of the present invention, in the crystal growth method for growing a group III nitride crystal from a melt in which at least an alkali metal, a group III metal, and nitrogen are dissolved, lithium (Li) is added to the melt. Inclusion of lithium increases the nitrogen concentration in the melt and increases the growth rate of the group III nitride crystal in the direction perpendicular to the c-axis to be higher than the growth rate in the direction parallel to the c-axis. A quality plate-like group III nitride crystal can be grown.

  In addition, a group III nitride crystal grown using a melt containing lithium has a high resistance of several MΩ or more without mixing special impurities. Therefore, a high-quality high-resistance substrate can be produced using the group III nitride crystal of the present invention.

  According to the invention of claim 6, since it is a group III nitride crystal grown by the crystal growth method according to any one of claims 1 to 5, high-quality group III nitriding Physical crystals can be provided.

  Further, according to the seventh aspect of the invention, since it is a semiconductor device using the group III nitride crystal according to the sixth aspect, it is possible to provide a semiconductor device with higher performance and higher reliability than the prior art. That is, since the group III nitride crystal constituting the semiconductor device of the present invention has few defects that adversely affect the performance of the semiconductor device, it is possible to provide a semiconductor device with higher performance and higher reliability than before.

  According to the invention of claim 8, in the semiconductor device of claim 7, the semiconductor device is a light emitting element having a semiconductor laminated structure laminated on the group III nitride crystal of claim 6. The light emitting element has few defects and has a long life even in high output operation. Accordingly, it is possible to provide a highly reliable light-emitting element that can operate at a higher output than the conventional one.

  According to the invention of claim 9, in the semiconductor device according to claim 7, the semiconductor device is a light receiving element formed using the group III nitride crystal according to claim 6. There are few defects in the group III nitride crystal, and the dark current is small. Therefore, it is possible to provide a highly sensitive light receiving element having a lower noise level and a higher S / N ratio.

  According to the invention of claim 10, in the semiconductor device of claim 7, the semiconductor device is an electronic device formed using the group III nitride crystal of claim 6. There are few defects in the group III nitride crystal. Therefore, abnormal diffusion of the electrode material and short circuit under a high electric field are improved as compared with the conventional case, and a highly reliable high-performance electronic device can be provided.

According to the invention of claim 11, since the system comprises the semiconductor device according to any one of claims 7 to 10, the system has higher performance and higher reliability than the prior art. A sex system can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described.

(First form)
The first aspect of the present invention is a crystal growth method for growing a group III nitride crystal from a melt in which at least an alkali metal, a group III metal, and nitrogen are dissolved. In the crystal growth method, the c-axis of the group III nitride crystal is included in the melt. It is characterized by containing a substance that controls the ratio between the growth rate in the direction and the growth rate in the direction perpendicular to the c-axis.

  As such a substance, as shown in the second embodiment, for example, there is a substance that makes the growth rate of the group III nitride crystal in the direction perpendicular to the c-axis higher than the growth rate in the direction parallel to the c-axis. . Specifically, lithium (Li) is an example of such a substance. By adding lithium to the melt, a plate crystal having a short c-axis direction can be grown. It is also within the scope of the present invention to control the growth rates of the group III nitride crystal in the c-axis direction and the growth rate in the direction perpendicular to the c-axis in the same manner.

  In the first embodiment, in a crystal growth method for growing a group III nitride crystal from a melt in which at least an alkali metal, a group III metal, and nitrogen are dissolved, the group III nitride crystal is grown in the c-axis direction in the melt. Since a substance that controls the ratio between the speed and the growth speed in the direction perpendicular to the c-axis is included, the morphology of the crystal can be controlled.

(Second form)
According to a second aspect of the present invention, in the crystal growth method according to the first aspect, the growth rate in the direction perpendicular to the c-axis of the group III nitride crystal is made higher in the melt than the growth rate in the c-axis direction. It is characterized by growing a group III nitride crystal containing a substance.

  In the second embodiment, in the crystal growth method of the first embodiment, the melt contains a substance that makes the growth rate in the direction perpendicular to the c-axis of the group III nitride crystal faster than the growth rate in the c-axis direction. In addition, since the group III nitride crystal is grown, the crystal form can be controlled to a plate shape. And since it can control to plate shape, it can use as it is as a board | substrate and the cost reduction of board | substrate manufacture is attained.

(Third form)
A third aspect of the present invention uses a seed crystal (for example, a plate-shaped seed crystal) in the crystal growth method of the first or second aspect, and uses the seed crystal (for example, a plate-shaped seed crystal) as the main surface. A group III nitride crystal is grown on the main surface of a seed crystal (for example, a plate-shaped seed crystal) at a growth rate in a direction parallel to the crystal surface, which is faster than a growth rate in a direction perpendicular to the main surface of the seed crystal. It is characterized by.

  In the third mode, in the crystal growth method of the first or second mode, a seed crystal (for example, a plate-shaped seed crystal) is used, which is parallel to the main surface of the seed crystal (for example, a plate-shaped seed crystal). The group III nitride crystal is grown on the main surface of the seed crystal at a higher growth rate in the direction than the growth rate in the direction perpendicular to the main surface of the seed crystal, so a crystal with a flat surface as the main surface is grown. Can be made.

(4th form)
According to a fourth aspect of the present invention, in the crystal growth method of the third aspect, a group III nitride crystal (plate-like group III nitride crystal) having a c-plane as a main surface is used as a seed crystal. It is characterized by growing a group III nitride crystal on the c-plane.

  In the fourth embodiment, in the crystal growth method of the third embodiment, a group III nitride crystal (plate-like group III nitride crystal) having a c-plane as a main surface is used as a seed crystal, and the c-plane of the seed crystal is formed. Since the group III nitride crystal is grown, it is possible to grow a group III nitride crystal having a high quality and a flat c-plane as a main surface.

(5th form)
According to a fifth aspect of the present invention, in the crystal growth method for growing a group III nitride crystal from a melt in which at least an alkali metal, a group III metal, and nitrogen are dissolved, lithium (Li) is included in the melt. It is characterized by.

  In a fifth aspect, in a crystal growth method for growing a group III nitride crystal from a melt in which at least an alkali metal, a group III metal, and nitrogen are dissolved, lithium (Li) is contained in the melt, thereby Increases the nitrogen concentration in the melt and increases the growth rate of the group III nitride crystal in the direction perpendicular to the c-axis to be higher than the growth rate in the direction parallel to the c-axis. Group nitride crystals can be grown.

  In addition, a group III nitride crystal grown using a melt containing lithium has a high resistance of several MΩ or more without mixing special impurities. Therefore, a high-quality high-resistance substrate can be produced using the group III nitride crystal of the present invention.

(Sixth form)
A sixth aspect of the present invention is a group III nitride crystal grown by the crystal growth method of any one of the first to fifth aspects. In the following table (Table 1), at least an alkali metal, a group III metal, and nitrogen are used when grown without adding lithium to a melt in which at least an alkali metal, a group III metal, and nitrogen are dissolved. The characteristics of the group III nitride crystal are shown when lithium (Li) is contained in the melt in which the solution is dissolved and grown (when added).

(7th form)
The seventh aspect of the present invention is a semiconductor device using the group III nitride crystal of the sixth aspect.

(8th form)
According to an eighth aspect of the present invention, in the semiconductor device according to the seventh aspect, the semiconductor device is a light-emitting element having a semiconductor multilayer structure in which the semiconductor device is laminated on the group III nitride crystal according to the sixth aspect. .

  Here, the form of the light-emitting element is not particularly limited, and any light-emitting element having a semiconductor laminated structure laminated on a group III nitride crystal such as a light-emitting diode or a semiconductor laser may be used.

(9th form)
According to a ninth aspect of the present invention, in the semiconductor device according to the seventh aspect, the semiconductor device is a light receiving element formed using the group III nitride crystal according to the sixth aspect.

  Here, the light receiving element is a photoconductive cell, a pn junction photodiode, a heterojunction FET type light receiving element, a heterojunction bipolar phototransistor, or the like, and is not particularly limited.

(10th form)
According to a tenth aspect of the present invention, in the semiconductor device of the seventh aspect, the semiconductor device is an electronic device formed using the group III nitride crystal of the sixth aspect.

  Here, the form of the electronic device is not particularly limited, and may be an FET or an HBT. Also, the intended use is not particularly limited, such as a high-temperature operating device, a high-frequency device, a high-power electronic device, or the like.

(Eleventh form)
An eleventh aspect of the present invention is a system including the semiconductor devices of the seventh, eighth, ninth, and tenth aspects.

  The system may be, for example, an illuminating device using a semiconductor device (light emitting element) of the eighth embodiment as a light source, a full-color large display device, a traffic sign, or the like, or a semiconductor device (light emitting device) of the eighth embodiment. ) As a writing or reading light source, an electrophotographic apparatus using the semiconductor device (light emitting element) of the eighth embodiment as a writing light source, or a ninth embodiment. A flame sensor, a wavelength-selective detector, or the like including the semiconductor device (light receiving element) as an optical sensor, or a mobile communication system including the semiconductor device (electronic device) according to the tenth aspect. Also good. In addition, the system is not particularly limited as long as the system includes the semiconductor devices of the seventh, eighth, ninth, and tenth modes.

Example 1 is an example corresponding to the first, second, fifth, and sixth modes. In Example 1, Na (sodium) is used as an alkali metal, metal Ga (gallium) is used as a group III element source, nitrogen gas is used as a nitrogen source, and further, a Li (lithium) source is used. Li ₃ N (lithium nitride) was added, and GaN was grown as a group III nitride.

Here, Na, Ga, Li ₃ N was previously held in the melt holding container as a mixed melt, and nitrogen was dissolved and supplied from the gas phase into the melt during crystal growth, so that GaN was crystal grown. .

  FIG. 1 is a diagram illustrating a configuration example of a crystal growth apparatus used in the first embodiment.

  The crystal growth apparatus of FIG. 1 is provided with a melt holding vessel 12 for holding a melt 25 containing an alkali metal and a group III metal in a closed reaction vessel 11 made of stainless steel and performing crystal growth. Yes.

  The melt holding container 12 can be removed from the reaction container 11. The material of the melt holding container 12 is BN.

Further, the gas supply pipe 14 that allows the internal space 23 of the reaction vessel 11 to be filled with nitrogen (N ₂ ) gas, which is a nitrogen raw material, and adjusts the nitrogen (N ₂ ) pressure in the reaction vessel 11 is reacted. The container 11 is mounted through. Here, the pressure of the nitrogen gas can be adjusted by the pressure control device 16.

  The gas supply pipe 14 is branched by a valve 18 and can introduce Ar gas. Here, the pressure of Ar gas can be adjusted by the pressure control device 19.

  The total pressure in the reaction vessel 11 is monitored with a pressure gauge 22.

  A heater 13 is installed outside the reaction vessel 11.

  The reaction vessel 11 can be removed from the crystal growth apparatus at the valve 21 portion, and only the reaction vessel 11 portion can be put into the glove box for operation.

  The GaN crystal growth method in Example 1 using the crystal growth apparatus of FIG. 1 will be described below.

  First, the reaction vessel 11 is separated from the crystal growth apparatus at the valve 21 and placed in a glove box in an Ar atmosphere.

Next, Ga is added to the BN melt holding container 12 as a Group III metal raw material, and sodium (Na) as the alkali metal. The ratio of Na in the melt 25 was Na / (Na + Ga) = 0.7. Also, it puts the Li ₃ N as Li raw materials.

  Next, the melt holding container 12 is placed on the melt holding container holding base 26 and installed in the reaction container 11. Next, the reaction vessel 11 is sealed, the valve 21 is closed, and the inside of the reaction vessel 11 is shut off from the external atmosphere. Next, the reaction vessel 11 is taken out of the glove box and incorporated in the crystal growth apparatus. That is, the reaction vessel 11 is installed at a predetermined position with a heater 13 and connected to a nitrogen and argon gas supply line 14 at a valve 21 portion.

  Next, the valves 15 and 21 are opened, and nitrogen gas is introduced into the reaction vessel 11. At this time, the nitrogen pressure was set to 3.3 MPa by the pressure control device 16. This pressure is a pressure at which the total pressure in the reaction vessel 11 becomes 4 MPa when the temperature is raised to the crystal growth temperature (775 ° C.) in the apparatus used in this example.

  Next, the valve 15 is closed. Next, the valve 18 is opened, and Ar gas is put into the reaction vessel 11. At this time, the pressure was adjusted to 6.6 MPa by the pressure controller 19. In this case, the partial pressure of Ar in the reaction vessel 11 is 3.3 MPa. This pressure (6.6 MPa) is a pressure at which the total pressure in the reaction vessel 11 becomes 8 MPa when the temperature is raised to the crystal growth temperature (775 ° C.) in the apparatus used in this example. That is, the pressure is such that the partial pressures of nitrogen and Ar are each 4 MPa.

  Next, the valve 18 and the valve 21 are closed. Thereby, the reaction container 11 is sealed. Next, the heater 13 is energized and the melt 25 is heated from room temperature (27 ° C.) to the crystal growth temperature in one hour. The crystal growth temperature was 775 ° C. The pressure in the sealed reaction vessel 11 increased following the temperature increase, and the total pressure in the reaction vessel 11 reached 8 MPa when the crystal growth temperature reached 775 ° C. That is, the partial pressures of nitrogen and Ar were each 4 MPa.

  After maintaining for 300 hours in this state, the temperature is lowered to room temperature. When the reaction vessel 11 was opened after the completion of crystal growth, a colorless and transparent plate-like GaN 30 was grown on the inner wall of the melt holding vessel 12.

  When the same crystal growth was performed without adding Li in the melt, a large number of small columnar crystals and thin plate-like GaN having a c-plane as the main surface grew. On the other hand, when Li was mixed in the melt, only a large plate-like GaN crystal 30 as shown in FIG. 2 grew.

The grown plate-like GaN crystal 30 had a C-plane passing length of 4 mm or more and a thickness of 80 μm or more. The half width of the X-ray rocking curve was as narrow as 45-55 arcsec, and the defect density was 10 ⁶ cm ⁻² or less in the evaluation of etch pit density. Moreover, it was high resistance and semi-insulating.

Example 2 is an example corresponding to the third, fourth, fifth and sixth modes. In Example 2, Na (sodium) is used as an alkali metal, metal Ga (gallium) is used as a group III element source, nitrogen gas is used as a nitrogen source, and further, a Li (lithium) source is used. Li ₃ N (lithium nitride) was added, and GaN was grown as a group III nitride on the seed crystal.

Here, Na, Ga, Li ₃ N was previously held in the melt holding container as a mixed melt, and nitrogen was dissolved and supplied from the gas phase into the melt during crystal growth, so that GaN was crystal grown. .

  In addition, a plate-like GaN crystal having a c-plane as a main surface was used as a seed crystal.

  FIG. 3 is a diagram illustrating a configuration example of the crystal growth apparatus used in the second embodiment. The crystal growth apparatus of FIG. 3 is the same as the apparatus of FIG.

  Below, the crystal growth method of GaN in Example 2 using the crystal growth apparatus of FIG. 3 is demonstrated.

  First, the reaction vessel 11 is separated from the crystal growth apparatus at the valve 21 and placed in a glove box in an Ar atmosphere.

Next, a plate-like GaN crystal 32 having a c-plane as a main surface is placed as a seed crystal in the BN melt holding container 12. Next, Ga is added as a Group III metal raw material, and sodium (Na) is added as an alkali metal. The ratio of Na in the melt 25 was set to Na / (Na + Ga) = 0.4. Next, Li ₃ N was added as a Li raw material.

  Next, the melt holding container 12 is placed on the melt holding container holding base 26 and installed in the reaction container 11. Thereafter, crystal growth was performed in the same procedure as in Example 1.

  After crystal growth for 300 hours, a plate-like GaN crystal 33 having a flat surface and colorless and transparent was grown on the seed crystal 32 as shown in FIG.

  When the same crystal growth was performed without putting Li in the melt, a GaN crystal 34 with large surface irregularities was grown on the seed crystal 32 as shown in FIG. On the other hand, when Li was mixed in the melt, a GaN crystal 33 having a flat surface as shown in FIG. 4 grew.

The grown GaN 33 had a narrow half width of the X-ray rocking curve of 45-55 arcsec, and the defect density was 10 ⁶ cm ⁻² or less in the etch pit density evaluation. Moreover, it was high resistance and semi-insulating.

  Example 3 is a semiconductor laser which is an example of the semiconductor device (light emitting element) of the eighth mode.

  6 and 7 are diagrams showing a semiconductor laser of Example 3. FIG. FIG. 6 is a perspective view of the semiconductor laser of Example 3, and FIG. 7 is a cross-sectional view taken along a plane perpendicular to the light emitting direction.

  The semiconductor laser of Example 3 is manufactured with a group III nitride semiconductor multilayer structure laminated on an n-type GaN substrate 50 made of the GaN crystal of the sixth form.

That is, in FIGS. 6 and 7, a semiconductor laser stacked structure 400 includes an n-type GaN layer 40, an n-type Al _0.2 Ga _0.8 N clad layer 41 on an n-type GaN substrate 50 having a thickness of 250 μm, n-type GaN light guide layer 42, In _0.05 Ga _0.95 N / In _0.15 Ga _0.85 N quantum well active layer 43, p-type GaN light guide layer 44, p-type Al _0.2 Ga _{0. 8} N clad layer 45 and p-type GaN cap layer 46 are sequentially stacked, and are produced by crystal growth by MOCVD.

Then, the stacked structure 400 is etched leaving the p-type GaN cap layer 46 to the middle of the p-type Al _0.2 Ga _0.8 N cladding layer 45 in a stripe shape, and the current confinement ridge waveguide structure 51 is produced. Yes. This current confinement ridge waveguide structure is formed along the <1-100> direction of the GaN substrate.

An insulating film 47 made of SiO ₂ is formed on the surface of the laminated structure. An opening is formed in the insulating film 47 on the ridge 51. A p-side ohmic electrode 48 is formed on the surface of the p-type GaN cap layer 46 exposed at the opening.

  An n-side ohmic electrode 49 is formed on the back surface of the n-type GaN substrate 50. The n-side ohmic electrode 49 was formed by vapor deposition of Ti / Al, and the p-side ohmic electrode 48 was formed by vapor deposition of Ni / Au.

  Optical resonator surfaces 401 and 402 are formed perpendicular to the ridge 51 and the active layer 43. The optical resonator surfaces 401 and 402 are formed by cleaving the (1-100) plane perpendicular to the current confinement ridge waveguide structure 51 along the <1-100> direction of the GaN substrate.

  The n-side ohmic electrode 49 and the optical resonator surfaces 401 and 402 were formed after the back surface of the n-type GaN substrate 50 was polished to 80 μm.

  In the semiconductor laser of Example 3, carriers are injected into the active layer by injecting current into the p-side ohmic electrode 48 and the n-side ohmic electrode 49, and light emission and light amplification occur. , 402 emit laser beams 411 and 412.

  The semiconductor laser of Example 3 is produced by crystal growth of a laser structure on a substrate different from Group III nitride such as a conventional sapphire substrate, or a GaN substrate produced by vapor phase growth or other methods. Compared with the one produced above, the crystal structure of the laser structure laminated on the substrate is low and the crystal quality is high, so it has a long life even under high output operation.

  Example 4 is an example of the semiconductor device (light receiving element) of the ninth mode. FIG. 8 is a diagram illustrating a light receiving element according to the fourth embodiment.

  The light receiving element of Example 4 is manufactured by a group III nitride semiconductor multilayer structure stacked on an n-type GaN substrate 60 manufactured by a group III nitride crystal of the sixth form.

  Here, the thickness of the GaN substrate 60 is 300 μm.

  In the structure of the light receiving element of Example 4, an n-type GaN layer 61 and an insulating GaN layer 62 are stacked on an n-type GaN substrate 60, and a transparent Schottky electrode 63 made of Ni / Au is formed thereon. MIS type light receiving element.

  An ohmic electrode 64 made of Ti / Al is formed on the back surface of the n-type GaN substrate 60, and an electrode 65 made of Au is formed on a part of the upper portion of the transparent Schottky electrode 63.

  In the light receiving element of Example 4, when light (ultraviolet light) 601 is incident from the transparent Schottky electrode 63 side, carriers are generated and a photocurrent is extracted from the electrode.

  The light-receiving element of Example 4 is manufactured by crystal-growing the light-receiving element structure on a substrate different from the group III nitride such as a conventional sapphire substrate, GaN manufactured by vapor phase growth, or other methods. Compared to those fabricated on the substrate, the light-receiving element structure laminated on the substrate had low crystal defects and high crystal quality, so the dark current was small and the S / N ratio was high.

  Example 5 is an example of the semiconductor device (electronic device) according to the tenth aspect. FIG. 9 is a cross-sectional view of a semiconductor device (electronic device) of Example 5. The electronic device of Example 5 is a high electron mobility transistor (HEMT).

  The high electron mobility transistor (HEMT) of Example 5 is manufactured with a group III nitride semiconductor stacked structure stacked on a GaN substrate 70 manufactured with a high-resistance GaN crystal of the sixth mode obtained by crystal growth with addition of Li. Has been.

  Here, the thickness of the GaN substrate 70 is 300 μm.

  The structure of the high electron mobility transistor (HEMT) is a recess gate HEMT including an insulating GaN layer 71, an n-type AlGaN layer 72, and an n-type GaN layer 73 stacked on a GaN substrate 70.

  The gate portion of the n-type GaN layer 73 is etched to the n-type AlGaN layer 72, and a gate electrode 76 made of Ni / Au is formed on the n-type AlGaN layer 72. A drain electrode 75 and a source electrode 74 made of Ti / Al are formed on the n-type GaN layer 73 on both sides of the gate.

  The high electron mobility transistor (HEMT) of Example 5 was prepared by crystal growth of a high electron mobility transistor (HEMT) structure on a substrate different from a group III nitride such as a conventional sapphire substrate, Compared to those grown on GaN substrates produced by phase growth or other methods, the crystal defects of the high electron mobility transistor (HEMT) structure stacked on the substrate are low and the crystal quality is high, so defects An abnormal diffusion and short circuit of the electrode due to, was suppressed, the withstand voltage was high, and good frequency characteristics were exhibited.

  Example 6 is an example of the system of the eleventh aspect. That is, Example 6 is an illuminating device including the semiconductor device (light emitting element) of the eighth mode.

  FIG. 10 is a schematic diagram of a lighting apparatus according to the sixth embodiment. FIG. 11 is a circuit diagram of the illumination device of the sixth embodiment. FIG. 12 is a cross-sectional view of a white LED module that is a light source of the illumination device of the sixth embodiment. FIG. 13 is a cross-sectional view of an ultraviolet light emitting LED which is a light source of a white LED module.

  In the illumination device of the sixth embodiment, two white LED modules 902, a current limiting resistor 96, a DC power source 97, and a switch 98 are connected in series, and the white LED module 902 emits light when the switch 98 is turned on and off. It is supposed to let you.

  Here, the white LED module 902 has a structure in which the YAG phosphor 91 is applied to the ultraviolet light emitting LED 90. When a predetermined voltage is applied between the electrode terminals 94 and 95, the ultraviolet light emitting LED 90 emits light, the YAG phosphor 91 is excited by the ultraviolet light, and white light 901 is extracted.

  Here, the ultraviolet light emitting LED 90 is made of a group III nitride semiconductor laminated structure laminated on an n-type GaN substrate 80 made of a group III nitride crystal of the sixth form.

  The thickness of the GaN substrate 80 is 300 μm.

The structure of the ultraviolet light emitting LED 90 includes an n-type GaN layer 81, an n-type Al _0.1 Ga _0.9 N layer 82, an active layer 83 having an InGaN / GaN multiple quantum well structure, a p-type on an n-type GaN substrate 80. An Al _0.1 Ga _0.9 N layer 84 and a p-type GaN layer 85 are stacked, and a transparent ohmic electrode 86 made of Ni / Au is formed thereon. An electrode 87 for wire bonding made of Ni / Au is formed on the transparent ohmic electrode 86. An ohmic electrode 88 made of Ti / Al is formed on the back surface of the n-type GaN substrate 80.

  In this ultraviolet light emitting LED 90, by injecting current into the p-side electrode 87 and the n-side ohmic electrode 88, carriers are injected into the active layer to emit light, and ultraviolet light 801 is extracted outside the LED.

  The LED of Example 6 is manufactured by crystal-growing an LED structure on a substrate different from a group III nitride such as a conventional sapphire substrate, or a GaN substrate manufactured by vapor phase growth or other methods. Compared with the one produced above, the crystal structure of the LED structure laminated on the substrate is low and the crystal quality is high, so the luminous efficiency is high and the output operation is high.

  Therefore, the lighting fixture of Example 6 was produced by crystal-growing the LED structure on a substrate different from the group III nitride such as a conventional sapphire substrate, or by vapor phase growth or other methods. It is brighter and consumes less power than white LED lighting fixtures that use ultraviolet LEDs fabricated on a GaN substrate.

The present invention can be used for a blue-violet light source for optical disks, an ultraviolet light source (LD, LED), a blue-violet light source for electrophotography, a group III nitride electronic device, and the like.

1 is a diagram illustrating a configuration example of a crystal growth apparatus used in Example 1. FIG. 1 is a diagram showing a plate-like GaN crystal grown in Example 1. FIG. It is a figure which shows the structural example of the crystal growth apparatus used in Example 2. FIG. 4 is a diagram showing a plate-like GaN crystal grown in Example 2. FIG. It is a figure which shows the plate-like GaN grown on the plate-like GaN seed crystal without adding lithium. 6 is a perspective view of a semiconductor laser of Example 3. FIG. 7 is a cross-sectional view taken along a plane perpendicular to the light emission direction of the semiconductor laser of Example 3. FIG. 6 is a cross-sectional view of a light receiving element in Example 4. FIG. 6 is a cross-sectional view of an electronic device of Example 5. FIG. It is a schematic diagram of the illuminating device of Example 6. It is a circuit diagram of the illuminating device of Example 6. It is sectional drawing of the white LED module which is a light source of the illuminating device of Example 6. It is sectional drawing of the ultraviolet light emission LED which is a light source of the module of white LED of Example 6. FIG. It is a figure which shows the structural example of the crystal growth apparatus in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Reaction container 12 Melt holding container 13 Heater 14 Gas supply pipe 15, 18, 21 Valve 16, 19 Pressure regulator 17 Nitrogen supply pipe 20 Argon supply pipe 22 Pressure gauge 23 Internal space 24 Raw material GaN holding container 25 Melt 26 Melting Liquid holding vessel holding table 30 GaN columnar crystal 31 GaN columnar crystal 32 GaN seed crystal 33 GaN crystal grown 34 GaN crystal grown by conventional method 40 n-type GaN layer 41 n-type Al _0.2 Ga _0.8 N cladding layer 42 n-type GaN optical guide layer 43 In _0.05 Ga _0.95 N / In _0.15 Ga _0.85 N quantum well active layer 44 p-type GaN optical guide layer 45 p-type Al _0.2 Ga _0.8 N cladding Layer 46 p-type GaN cap layer 47 Insulating film 48 Ohmic electrode on p side 49 Ohmic electrode on n side 50 n-type Ga N substrate 51 Current confinement ridge waveguide structure 60 n-type GaN substrate 61 n-type GaN layer 62 insulating GaN layer 63 transparent Schottky electrode 64 ohmic electrode 65 electrode 70 GaN substrate 71 insulating GaN layer 72 n-type AlGaN layer 73 n-type GaN layer 74 Source electrode 75 Drain electrode 76 Gate electrode 80 n-type GaN substrate 81 n-type GaN layer 82 n-type Al _0.1 Ga _0.9 N layer 83 active layer having InGaN / GaN multiple quantum well structure 84 p-type Al _0.1 Ga _0.9 N layer 85 p-type GaN layer 86 transparent ohmic electrode 87 electrode 88 n-side ohmic electrode 90 ultraviolet light emitting LED
91 YAG phosphor 92 Gold wire 93 Lens 94, 95 Electrode terminal 96 Current limiting resistor 97 DC power supply 98 Switch 400 Laminated structure 401, 402 Optical resonator surface 411, 412 Laser light 601 Light (ultraviolet light)
801 Ultraviolet light 901 White light 902 White LED module

Claims (11)

In a crystal growth method for growing a group III nitride crystal from a melt in which at least an alkali metal, a group III metal, and nitrogen are dissolved, the growth rate in the c-axis direction of the group III nitride crystal and the c-axis direction are perpendicular to the melt. A method for growing a group III nitride crystal, comprising a substance that controls a growth rate in any direction. 2. The crystal growth method according to claim 1, wherein the melt includes a substance that makes a growth rate in a direction perpendicular to the c-axis of the group III nitride crystal faster than a growth rate in the c-axis direction. A method for growing a group III nitride crystal, characterized by growing a physical crystal. The crystal growth method according to claim 1 or 2, wherein a seed crystal is used, and a growth rate in a direction parallel to the main surface of the seed crystal is higher than a growth rate in a direction perpendicular to the main surface of the seed crystal. A group III nitride crystal growth method, comprising growing a group III nitride crystal on a main surface of a seed crystal. 4. The crystal growth method according to claim 3, wherein a group III nitride crystal having a c-plane as a main surface is used as a seed crystal, and a group III nitride crystal is grown on the c-plane of the seed crystal. Crystal growth method of objects. In a crystal growth method for growing a group III nitride crystal from a melt in which at least an alkali metal, a group III metal, and nitrogen are dissolved, lithium (Li) is included in the melt. Crystal growth method. A group III nitride crystal grown by the crystal growth method according to any one of claims 1 to 5. A semiconductor device using the group III nitride crystal according to claim 6. 8. The semiconductor device according to claim 7, wherein the semiconductor device is a light emitting element having a semiconductor laminated structure laminated on the group III nitride crystal according to claim 6. 8. The semiconductor device according to claim 7, wherein the semiconductor device is a light receiving element formed using the group III nitride crystal according to claim 6. 8. The semiconductor device according to claim 7, wherein the semiconductor device is an electronic device formed using the group III nitride crystal according to claim 6. A system comprising the semiconductor device according to any one of claims 7 to 10.

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