WO2010007983A1 - GaN結晶の成長方法 - Google Patents
GaN結晶の成長方法 Download PDFInfo
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- WO2010007983A1 WO2010007983A1 PCT/JP2009/062728 JP2009062728W WO2010007983A1 WO 2010007983 A1 WO2010007983 A1 WO 2010007983A1 JP 2009062728 W JP2009062728 W JP 2009062728W WO 2010007983 A1 WO2010007983 A1 WO 2010007983A1
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Images
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02365—Forming inorganic semiconducting materials on a substrate
- H01L21/02518—Deposited layers
- H01L21/02521—Materials
- H01L21/02538—Group 13/15 materials
- H01L21/0254—Nitrides
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/40—AIIIBV compounds wherein A is B, Al, Ga, In or Tl and B is N, P, As, Sb or Bi
- C30B29/403—AIII-nitrides
- C30B29/406—Gallium nitride
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B9/00—Single-crystal growth from melt solutions using molten solvents
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- H—ELECTRICITY
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02365—Forming inorganic semiconducting materials on a substrate
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- H—ELECTRICITY
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02365—Forming inorganic semiconducting materials on a substrate
- H01L21/02367—Substrates
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/02104—Forming layers
- H01L21/02365—Forming inorganic semiconducting materials on a substrate
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- H01L21/02625—Liquid deposition using melted materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/16—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a particular crystal structure or orientation, e.g. polycrystalline, amorphous or porous
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
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- H01L33/005—Processes
- H01L33/0062—Processes for devices with an active region comprising only III-V compounds
- H01L33/0075—Processes for devices with an active region comprising only III-V compounds comprising nitride compounds
Definitions
- the present invention relates to a method for growing a GaN crystal having a low dislocation density, which is preferably used as a substrate for various semiconductor devices such as light-emitting elements, electronic elements, and semiconductor sensors.
- the GaN crystal is very useful as a material for forming substrates of various semiconductor devices such as light emitting elements, electronic elements, and semiconductor sensors.
- a GaN crystal substrate having a low dislocation density and good crystallinity is required.
- a liquid phase method using a Ga-containing melt is a GaN crystal having a low dislocation density as compared with a vapor phase method such as HVPE (hydride vapor phase epitaxy) or MOCVD (metal organic chemical vapor deposition). Growth is expected to be possible.
- a vapor phase method such as HVPE (hydride vapor phase epitaxy) or MOCVD (metal organic chemical vapor deposition). Growth is expected to be possible.
- Patent Document 1 discloses a high temperature atmosphere of 1000 K to 2800 K (preferably 1600 K to 2800 K) and a high pressure atmosphere of 2000 atm to 45000 atm (preferably 10,000 to 45000 atm).
- a method of growing GaN crystals by dissolving nitrogen gas in Ga melt is disclosed.
- the crystal growth method of Patent Document 1 requires a high pressure of 2000 atm (202.6 MPa) to 45000 atm (4.56 GPa), preferably 10,000 atm (1.01 GPa) to 45000 atm (4.56 GPa). To do. In order to obtain such a high pressure, it is not sufficient to simply supply the compressed nitrogen gas to the crystal growth vessel, and a pressurizing device is required. Moreover, a pressure vessel that can withstand such high pressure is required. For this reason, there is a problem that a large-scale device is required.
- Non-Patent Document 1 A GaN crystal growth method using Na as a flux is disclosed.
- the crystal growth apparatus can be simplified compared to the crystal growth method of Patent Document 1. .
- the crystal growth method of Non-Patent Document 1 has a problem that Na is incorporated as an impurity in the growing GaN crystal because metal Na is contained in the melt used for crystal growth.
- the present invention solves the above problems in a liquid phase method using a Ga-containing melt, and does not add impurities other than raw materials (gallium and nitrogen) to the melt, and enlarges the crystal growth apparatus.
- An object of the present invention is to provide a method for growing a GaN crystal having a low dislocation density and high crystallinity.
- the present invention one main surface a substrate having a step of preparing a substrate comprising a Ga x Al y In 1-xy N (0 ⁇ x, 0 ⁇ y, x + y ⁇ 1) seed crystal having a main surface thereof And a main surface of the substrate is brought into contact with a solution in which nitrogen is dissolved in a Ga melt, and GaN is formed on the main surface at an atmospheric temperature of 800 ° C. to 1500 ° C. and an atmospheric pressure of 500 atm. And a step of growing a crystal.
- the GaN crystal growth method according to the present invention may further include a step of etching the main surface of the substrate after the step of preparing the substrate and before the step of growing the GaN crystal.
- the step of etching the main surface of the substrate is performed by bringing the main surface of the substrate into contact with a solution in which nitrogen is dissolved in a Ga melt, and an atmospheric temperature of 800 ° C. or higher and 1500 ° C. or lower and 1 atm or higher and lower than 500 atm. Under atmospheric pressure.
- the substrate is Ga x Al y In 1-xy N seed crystal to the main crystal regions and the main crystal regions [0001] direction polarity reversed crystal region whose polarity is reversed in Can be included.
- the substrate can be recessed with a depth of 10 ⁇ m or more in the main surface of the polarity reversal crystal region compared to the main surface of the main crystal region.
- a plurality of substrates are prepared, a plurality of crystal growth containers containing one or more substrates are prepared, and a plurality of crystal growth containers are provided in the crystal growth chamber.
- the present invention in the liquid phase method using Ga melt, the above problems are solved, and the crystal growth apparatus is enlarged without adding impurities other than raw materials (gallium and nitrogen) to the melt. Therefore, a method for growing a GaN crystal having a low dislocation density and high crystallinity can be provided.
- (a) shows a step of preparing a substrate
- (b) shows a step of etching the surface of the substrate
- (c) shows a step of growing a GaN crystal.
- (a) shows a step of preparing a substrate
- (b) shows a step of etching the surface of the substrate
- (c) shows a step of growing a GaN crystal.
- It is the schematic which shows an example of the crystal growth container in which the board
- (a) is a schematic top view of the crystal growth vessel, and (b) is a schematic cross-sectional view taken along VB-VB of (a). It is the schematic which shows the other example of the crystal growth container in which the board
- (a) shows a schematic top view of the crystal growth vessel, and (b) shows a schematic cross-sectional view taken along VIB-VIB of (a). It is a schematic top view which shows an example of arrangement
- a substrate 10 having a principal surface 10m, Ga x Al y In 1 -xy N with its main surface 10 m ( 0 ⁇ x, 0 ⁇ y, x + y ⁇ 1, the same applies hereinafter)
- an atmospheric temperature 800 ° C. or higher and 1500 ° C. or lower and an atmospheric pressure of 500 atmospheres (50.7 MPa) or more and less than 2000 atmospheres (202.6 MPa)
- a step of growing the GaN crystal 20 By contacting the solution 7 which has been brought into contact with it, an atmospheric temperature of 800 ° C. or higher and 1500 ° C. or lower and an atmospheric pressure of 500 atmospheres (50.7 MPa) or more and less than 2000 atmospheres (202.6 MPa)
- a step of growing the GaN crystal 20 By contacting the solution 7 which has been brought into contact with it,
- method for growing a GaN crystal of the present embodiment is a substrate 10 having a principal surface 10m, Ga x Al y In 1 -xy N with its main surface 10m
- a step of preparing the substrate 10 including the seed crystal 10a is provided.
- a large GaN crystal having a low dislocation density and high crystallinity can be easily grown on the main surface 10 m of the Ga x Al y In 1-xy N seed crystal 10 a of the substrate 10. .
- the substrate 10 having a principal face 10m is sufficient if it contains Ga x Al y In 1-xy N seed crystal 10a having the main surface 10m, Ga x Al y In 1 -xy on a base substrate 10b may be a template substrate where N seed crystal 10a is formed, Ga x Al y in 1- xy N seed crystal free-standing substrate whole substrate is made of Ga x Al y in 1-xy N seed crystal 10a It may be. If substrate 10 is a template substrate, the base substrate 10b, Ga x Al y In 1 -xy N seed crystal 10a and lattice mismatch is small sapphire substrate, SiC substrate, such as GaAs substrate is preferably used.
- a method of forming a Ga x Al y In 1-xy N seed crystal 10a on underlying substrate 10b is not particularly limited, HVPE (hydride vapor phase epitaxy) method, MOCVD (metal organic chemical vapor deposition) Examples thereof include a gas phase method such as a method, and a liquid phase method such as a melt method.
- HVPE hydrogen vapor phase epitaxy
- MOCVD metal organic chemical vapor deposition
- the Ga x Al y In 1-xy N seed crystal 10a preferably has a larger Ga composition ratio.
- 0.5 ⁇ x ⁇ 1 It is preferable that 0.75 ⁇ x ⁇ 1.
- GaN crystal growth method of the present embodiment nitrogen is dissolved in Ga melt 3 on main surface 10m of substrate 10 (dissolution of nitrogen in Ga melt 5).
- GaN crystals In the growth of GaN crystals by a conventional liquid phase method using Ga melt, a high temperature of 1000 K (727 ° C.) to 2800 K (2527 ° C.) and a high pressure of 2000 atmospheres (202.6 MPa) to 45000 atmospheres (4.56 GPa) are used. Needed. In contrast, contact the Ga x Al y In 1-xy N seed crystal 10a dissolved nitrogen in the Ga melt 3 on the main surface 10m of (dissolution of nitrogen into the Ga melt 5) is the solution 7 was the substrate 10 This makes it possible to grow a GaN crystal even under an atmospheric temperature of 800 ° C. or higher and 1500 ° C. or lower and an atmospheric pressure of 500 atmospheres (50.7 MPa) or more and less than 2000 atmospheres (202.6 MPa).
- the dissolution 5 of nitrogen in the Ga melt 3 is not particularly limited, but is performed by bringing a nitrogen-containing gas into contact with the Ga melt 3 from the viewpoint of easy control of the amount of nitrogen to be dissolved. Is preferred.
- the atmospheric pressure is obtained by dissolving a nitrogen-containing gas in the Ga melt 3 (dissolution of nitrogen in the Ga melt 5).
- Ga Ga more than purity 99.99 mass% is preferable, and purity 99 More preferable is 9999% by mass or more of Ga.
- the nitrogen-containing gas is not particularly limited, and nitrogen (N 2 ) gas, ammonia (NH 3 ) gas, and the like can be used.
- high purity Nitrogen gas is preferable, for example, nitrogen gas having a purity of 99.99% by mass or more is preferable, and nitrogen gas having a purity of 99.9999% by mass or more is more preferable.
- the ambient temperature is less than 800 ° C
- the crystal growth is slow and enormous time is required to obtain a crystal of practical size.
- the ambient temperature is higher than 1500 ° C
- the decomposition is more likely to proceed than the crystal growth. Crystals cannot be obtained.
- the atmospheric pressure is less than 500 atmospheres
- the crystal growth is slow and enormous time is required to obtain crystals of practical size, and if it is over 2000 atmospheres, a special pressurizing mechanism is required for the crystal growth apparatus. This increases the cost for crystal growth.
- FIG. 2 another embodiment of the method for growing a GaN crystal according to the present invention is a step of growing a GaN crystal in Embodiment 1 after the step of preparing a substrate (FIG. 2 (a)).
- a step of etching the main surface 10m of the substrate 10 Prior to FIG. 2C, is further provided.
- Etching the main surface 10m of the substrate 10 removes a work-affected layer generated on the substrate when preparing the substrate or a surface oxide layer generated after preparing the substrate, so that the dislocation density is formed on the main surface of the substrate. It is possible to grow a GaN crystal having a very low crystallinity and a very high crystallinity.
- the method for etching the main surface 10m of the substrate 10 is not particularly limited, but a method in which the surface can be directly transferred to the crystal growth step without being exposed to the air after etching, for example, nitrogen is dissolved in the Ga melt 3 ( A method of etching using a solution 7 in which nitrogen is dissolved in Ga melt is preferable. This is because, even if the main surface 10m of the substrate 10 is etched in advance, a surface oxide layer is always formed on the main surface 10m in the preparation stage used for Ga solution growth, and dirt or the like adheres to the main surface 10m. This is because defects occur when grown.
- the method for growing a GaN crystal of the present embodiment is a substrate 10 having a principal surface 10m, Ga x Al y In 1 -xy N with its main surface 10m (0 ⁇ x, 0 ⁇ y, x + y ⁇ 1) including a step of preparing a substrate including the seed crystal 10a. This process is as described in the first embodiment.
- the method for growing a GaN crystal according to this embodiment includes a step of etching the main surface 10 m of the substrate 10. Since the surface layer 10e of the substrate 10 before etching includes a work-affected layer generated on the substrate when the substrate is prepared, a surface oxide layer generated after the substrate is prepared, or dirt attached to the substrate. Thus, the main surface 10m from which the surface layer 10e is removed is obtained.
- the step of etching the main surface 10m of the substrate 10 is not particularly limited, but nitrogen is dissolved in the Ga melt 3 (dissolution of nitrogen into the Ga melt 5) in the main surface 10m of the substrate 10. It is preferable that the solution 7 is brought into contact with each other at an atmospheric temperature of 800 ° C. to 1500 ° C. and an atmospheric pressure of 1 atm (0.1 MPa) to less than 500 atm (50.7 MPa).
- the dissolution 5 of nitrogen in the Ga melt 3 is not particularly limited, but is performed by bringing a nitrogen-containing gas into contact with the Ga melt 3 from the viewpoint of easy control of the amount of nitrogen to be dissolved. Is preferred.
- the atmospheric pressure is obtained by dissolving a nitrogen-containing gas in the Ga melt 3 (dissolution of nitrogen in the Ga melt 5).
- the etching rate of the main surface meaning the rate at which the main surface is etched; the same applies hereinafter
- the etching rate of the surface becomes too high, making it difficult to control the etching process.
- the atmospheric pressure is less than 1 atm, the etching rate of the main surface becomes too high and the etching process is difficult to control, and if it is more than 500 atm, the etching rate of the main surface is small and a long time is required for the etching process. .
- FIG. 3 yet another embodiment of the method for growing a GaN crystal of the present invention is the embodiment 1 or embodiment 2, the substrate 10 is, Ga x Al y In 1- xy N seed crystal 10a is A main crystal region 10k and a polarity-inverted crystal region 10h in which the polarity in the [0001] direction is inverted with respect to the main crystal region 10k. Since the substrate 10 has a lower dislocation density in the main crystal region than the substrate of the first or second embodiment, the dislocation density is higher on the main surface 10 km of the main crystal region 10 k of the substrate 10. A GaN crystal 20 having lower crystallinity and higher crystallinity can be grown.
- method for growing a GaN crystal of the present embodiment is a substrate 10 having a principal surface 10m, Ga x Al y In 1 -xy N with its main surface 10m (0 ⁇ x, 0 ⁇ y, x + y ⁇ 1) including a step of preparing the substrate 10 including the seed crystal 10a.
- substrate 10 to be prepared in the present embodiment Ga x Al y In 1- xy N seed crystal 10a polarity reversed crystal region 10h which the polarity of the [0001] direction with respect to the main crystal regions 10k and a main crystal regions 10k is inverted Including.
- the polarity reversed crystal region 10h is not particularly limited, and is formed to be viewed from the main surface 10 m, for example stripes or dots. Further, when viewed from the main surface 10m, the width of the polarity reversal crystal region 10h is, for example, 5 ⁇ m to 200 ⁇ m, and the pitch of the polarity reversal crystal region 10h is, for example, 50 ⁇ m to 2000 ⁇ m.
- Method of growing Ga x Al y In 1-xy N seed crystal 10a of the substrate 10 to be prepared in the present embodiment is not particularly limited, forming a facet, as described in JP-A-2003-183100 For example, a facet growth method in which a crystal is grown while maintaining it.
- Ga x Al y In 1-xy N seed crystal 10a thus obtained has a low dislocation density main crystal regions 10k, and has inverted the polarity of the [0001] direction with respect to the main crystal regions 10k main crystal regions 10k The polarity inversion crystal region 10h having a dislocation density higher than that of FIG.
- the GaN crystal growth method of this embodiment includes a step of etching the main surface 10 m of the substrate 10.
- the step of etching the main surface 10m of the substrate 10 is performed in the same manner as in the second embodiment.
- by the etching process it is etched at about the same rate as the Ga x Al y In 1-xy N species main surface 10hm polarity reversed crystal region 10h of the crystal 10a is the main crystal regions 10k of the main surface 10km .
- Ga x Al y In 1- xy N seed crystal 10a of the substrate 10 of the present embodiment as compared with the lower main crystal regions 10k and a main crystal regions 10k dislocation density [0001] polarity of the direction is reversed dislocation density And a high polarity inversion crystal region 10h. Therefore, when the GaN crystal 20 is grown on the main surface 10m of the Ga x Al y In 1-xy N seed crystal 10a of the substrate 10, the polarity and the low dislocation density are inherited on the main crystal region 10k of the substrate 10.
- the main crystal region 20k of the GaN crystal grows, and the polarity and the high dislocation density are inherited on the polarity reversal crystal region 10h of the substrate 10, so that the polarity in the [0001] direction is reversed and the dislocation density compared to the main crystal region 20k.
- a high polarity inversion crystal region 20h grows.
- the main crystal region 20k having a low dislocation density of the GaN crystal 20 can be grown on the main surface 10km of the main crystal region 10k of the substrate 10.
- FIG. 4 yet another embodiment of the method for growing a GaN crystal of the present invention is the embodiment 1 or embodiment 2, the substrate 10 is, Ga x Al y In 1- xy N seed crystal 10a is The main crystal region 10k and the polarity-inverted crystal region 10h whose polarity in the [0001] direction is inverted with respect to the main crystal region 10k are included, and the main surface 10hm of the polarity-inverted crystal region 10h is compared with the main surface 10km of the main crystal region 10k. Is recessed at a depth D of 10 ⁇ m or more.
- the substrate 10 has a main surface 10 hm of the polarity reversal crystal region 10 h that is recessed at a depth D of 10 ⁇ m or more compared to the main surface 10 km of the main crystal region 10 k.
- the polarity reversal crystal region of the GaN crystal does not grow on the main surface 10hm of the polarity reversal crystal region 10h, and the main crystal region 20k grown on the main surface 10km of the main crystal region 10k is joined and integrated at the junction crystal region 20c.
- a GaN crystal 20 is obtained.
- the GaN crystal 20 inherits the polarity of the main crystal region 10k of the Ga x Al y In 1-xy N seed crystal 10a of the substrate 10 and has a low dislocation density and high crystallinity except for the junction crystal region 20c.
- the method for growing a GaN crystal of the present embodiment is a substrate 10 having a principal surface 10m, Ga x Al y In 1 -xy N with its main surface 10m (0 ⁇ x, 0 ⁇ y, x + y ⁇ 1) including a step of preparing the substrate 10 including the seed crystal 10a.
- Substrate 10 to be prepared in the present embodiment Ga x Al y In 1- xy N seed crystal 10a polarity reversed crystal region 10h which the polarity of the [0001] direction with respect to the main crystal regions 10k and a main crystal regions 10k is inverted Including.
- substrate 10 prepared in this embodiment is the same as the board
- the main surface 10 hm of the polarity reversal crystal region 10 h is recessed with a depth D of 10 ⁇ m or more as compared with the main surface 10 km of the main crystal region 10 k.
- the depth D of the recess 10v (more specifically, the recess 10v before etching) of the main surface 10hm of the polarity reversal crystal region 10h with respect to the main surface 10km of the main crystal region 10k is determined after the next main surface 10m etching step.
- the etching rate of the main surface 10 km of the main crystal region 10 k may be higher than the etching rate of the main surface 10 hm of the polarity reversal crystal region 10 h.
- the substrate 10 prepared in the present embodiment is a method in which the main surface 10m of the substrate 10 prepared in the third embodiment is subjected to vapor phase etching using a chlorine-containing gas (for example, HCl gas, Cl 2 gas, etc.). And a liquid phase etching method using a strong acid such as hot phosphoric acid or a strong base such as molten KOH or molten NaOH.
- a chlorine-containing gas for example, HCl gas, Cl 2 gas, etc.
- a liquid phase etching method using a strong acid such as hot phosphoric acid or a strong base such as molten KOH or molten NaOH.
- the etching rate of the main surface 10hm of the polarity reversal crystal region 10h (the rate at which the main surface is etched) is higher than the etching rate of the main surface 10hm of the main crystal region 10k.
- the main surface 10hm of the polarity reversal crystal region 10h can be recessed with respect
- the GaN crystal growth method of this embodiment includes a step of etching the main surface 10 m of the substrate 10.
- the step of etching the main surface 10m of the substrate 10 is performed in the same manner as in the second embodiment.
- by the etching process it is etched at about the same rate as the Ga x Al y In 1-xy N species main surface 10hm polarity reversed crystal region 10h of the crystal 10a is the main crystal regions 10k of the main surface 10km .
- the main surface 10 hm of the polarity inversion crystal region 10 h is recessed with respect to the main surface 10 km of the main crystal region 10 k.
- the GaN crystal growth method of this embodiment nitrogen is dissolved in the Ga melt 3 on the main surface 10m of the substrate 10 (dissolution of nitrogen in the Ga melt 5). ) To bring the GaN crystal 20 on the main surface 10 m under an atmospheric temperature of 800 ° C. or higher and 1500 ° C. or lower and an atmospheric pressure of 500 atmospheric pressure or higher and lower than 2000 atmospheric pressure.
- a GaN crystal is grown on the main surface 10 m after etching the substrate. Therefore, compared to the GaN crystal obtained in the first embodiment, the dislocation density is smaller and the crystallinity is reduced. A higher GaN crystal is obtained.
- Ga x Al y In 1- xy N seed crystal 10a of the substrate 10 of the present embodiment as compared with the lower main crystal regions 10k and a main crystal regions 10k dislocation density [0001] polarity of the direction is reversed dislocation density And the main surface 10hm of the polarity reversal crystal region 10h is recessed as compared to the main surface 10km of the main crystal region 10k.
- the inverted crystal region does not grow, and the main crystal region 20k grown on the main surface 10km of the main crystal region 10k grows.
- a plurality of main crystal regions 20k are joined at one or more junction crystal regions 20c to form an integrated GaN crystal 20.
- the GaN crystal 20 thus obtained inherits the polarity of the main crystal region 10k of the Ga x Al y In 1-xy N seed crystal 10a of the substrate 10 and has a low dislocation density and high crystallinity except for the junction crystal region 20c.
- a plurality of substrates 10 are prepared in the step of preparing a substrate in the embodiments 1 to 4.
- a plurality of crystal growth vessels 1, 1A, 1B containing two or more substrates 10 are prepared, and the plurality of crystal growth vessels 1, 1A, 1B are placed in the crystal growth chamber 110 in at least one of a horizontal direction and a vertical direction. Place them side by side.
- the present embodiment referring to FIG. 8, it is possible to grow a plurality of GaN crystals 20 at a time by growing a GaN crystal 20 on each substrate 10 of the plurality of substrates 10. Large GaN crystals with low density and high crystallinity can be efficiently grown in large quantities. Further, the plurality of GaN crystals 20 can be grown at a time by etching the main surfaces 10m of the plurality of substrates 10 at a time and growing the GaN crystals 20 on each of the etched substrates 10. And large GaN crystals with extremely low dislocation density and extremely high crystallinity can be efficiently grown in large quantities.
- the crystal growth vessels 1, 1A, 1B used in the present embodiment there are no particular limitations on the crystal growth vessels 1, 1A, 1B used in the present embodiment as long as they do not adversely affect the growth of the GaN crystal.
- carbon (C) For example, a crucible made of pyrolytic boron nitride (pBN) or alumina (Al 2 O 3 ) is used.
- the crystal growth containers 1A and 1B in which one or more substrates 10 are accommodated are sufficient, and even in the crystal growth container 1A in which one substrate 10 illustrated in FIG. It may be a crystal growth vessel 1B in which the substrate 10 is accommodated.
- the arrangement of the plurality of substrates 10 accommodated in the crystal growth vessel 1B is not particularly limited, but from the viewpoint of arranging as many substrates 10 as possible in a predetermined region, the plurality of substrates 10 are arranged. It is preferable to arrange them in a direction parallel to the main surface 10 m of the substrate 10. From this point of view, it is more preferable that the plurality of substrates 10 be arranged side by side so as to be dense on a surface parallel to the main surface 10m of the substrate 10, and it is more preferable that they are arranged side by side so as to be dense.
- the plurality of substrates are in the shape of a disk having the same radius, it is preferable to arrange the substrates 10 side by side so as to be hexagonally dense in a plane as shown in FIG.
- the substrate 10 having a main surface 10m, as shown in the embodiment 1 or embodiment 2, sufficient if it contains Ga x Al y In 1-xy N seed crystal 10a having the principal face 10m, basal on the substrate 10b Ga x Al y in 1- xy N species may be a template substrate in which the crystal 10a is formed, Ga entire substrate is made of Ga x Al y in 1-xy N seed crystal 10a a x Al y in 1-xy N seed crystal free-standing substrate may be.
- Ga x Al y In 1 -xy N seed crystal 10a is, as compared with the lower main crystal regions 10k and a main crystal regions 10k dislocation density [0001] direction of the polar And a polarity inversion crystal region 10h having a high dislocation density.
- the substrate 10 as shown in the embodiment 4, Ga x Al y In 1 -xy N seed crystal 10a main crystal regions 10k and a main crystal regions 10k to [0001] the polarity inversion the polarity of the direction is reversed
- the main surface 10hm of the polarity reversal crystal region 10h may be recessed with a depth D of 10 ⁇ m or more as compared with the main surface 10km of the main crystal region 10k.
- crystal growth containers 1, 1 A, 1 B in which one or more substrates are accommodated are arranged in crystal growth chamber 110 in at least one of the horizontal direction and the vertical direction. As long as they are arranged side by side, they may be arranged in the horizontal direction as shown in the uppermost stage of FIG. 7 or FIG. 8, or arranged in the vertical direction as shown in stages other than the uppermost stage of FIG. May be.
- the crystal growth vessels 1A and 1B are arranged in the vertical direction, but from the viewpoint of arranging as many crystal growth vessels as possible in a predetermined region, they are arranged so as to be dense in the vertical direction. It is preferable.
- the crystal growth chamber 110 is provided with a gas supply port 110e for supplying a nitrogen-containing gas into the chamber. Further, a heater 120 for heating the inside of the crystal growth chamber 110 is disposed outside the crystal growth chamber 110.
- Example 1 Preparation of Substrate Referring to FIG. 1A, a GaN seed having a thickness of 3 ⁇ m is formed on a (0001) main surface of a sapphire substrate (basic substrate 10b) having a diameter of 2 inches (5.08 cm) as a substrate 10 by MOCVD. Crystal (Ga x Al y In 1- xy N seed crystal 10a) was prepared GaN template substrate was grown. The dislocation density of the GaN seed crystal of this GaN template substrate was 1 ⁇ 10 9 cm ⁇ 2 as measured by the CL (cathode luminescence) method.
- CL cathode luminescence
- the above GaN template is placed in a carbon crucible (crystal growth vessel 1) having an inner diameter of 6 cm and a height of 5 cm arranged in a crystal growth chamber (not shown).
- a substrate (substrate 10) and 85 g of metal Ga having a purity of 99.9999% by mass were arranged.
- the crucible (crystal growth vessel 1) is kept at room temperature (25 ° C.) over 2 hours from atmospheric pressure to 1950 atm (197). Then, the pressure was further maintained at 1950 atm and heated from room temperature to 1100 ° C. over 3 hours. At this time, the metal Ga disposed in the crucible is melted to become the Ga melt 3, and the solution 7 obtained by the dissolution 5 of nitrogen in the Ga melt 3 is in contact with the main surface 10 m of the substrate 10. The crucible was then held for 10 hours under a nitrogen atmosphere of 1950 atm and 1100 ° C.
- a GaN crystal 20 having a thickness of 5 ⁇ m was grown on the main surface 10 m of the GaN template substrate (substrate 10).
- the thickness of the GaN crystal was measured by observing a cross section in the crystal growth direction of the crystal grown on the substrate by SEM (scanning electron microscope). Further, the half width of the X-ray diffraction peak related to the (0002) plane of the GaN crystal was 780 arcsec.
- the dislocation density of the GaN crystal was 2 ⁇ 10 8 cm ⁇ 2 as measured by the CL method, which was lower than the dislocation density of the GaN seed crystal of the substrate.
- Example 2 Preparation of Substrate With reference to FIG. 2A, a GaN template substrate (substrate 10) similar to that of Example 1 was prepared.
- the crucible (crystal growth vessel 1) is kept at 30 atm (3.04 MPa) at room temperature (25 ° C.) over 3 hours. To 1100 ° C. At this time, the metal Ga disposed in the crucible is melted to become the Ga melt 3, and the solution 7 obtained by the dissolution 5 of nitrogen in the Ga melt 3 is in contact with the main surface 10 m of the substrate 10. However, under this condition, since there is little dissolution of nitrogen in the Ga melt, the main surface 10m of the GaN seed crystal of the GaN template substrate is etched without growing the GaN crystal.
- nitrogen gas having a purity of 99.999 mass% is supplied into a crystal growth chamber (not shown), and the crucible (crystal growth vessel 1) is While maintaining at 1100 ° C., the pressure was increased from 30 atm (3.04 MPa) to 1950 atm (197.5 MPa) over 2 hours. The crucible was then held for 10 hours under a nitrogen atmosphere of 1950 atm and 1100 ° C.
- the dissolution of nitrogen in the Ga melt in contact with the main surface 10 m of the substrate increased, and a GaN crystal grew.
- the thickness of the GaN crystal was 5 ⁇ m
- the half-value width of the X-ray diffraction peak related to the (0002) plane of the GaN crystal was 360 arcsec, and it had high crystallinity.
- the dislocation density of the GaN crystal was 7 ⁇ 10 6 cm ⁇ 2 , which was lower than the dislocation density of the GaN seed crystal of the substrate and the GaN crystal of Example 1.
- Example 2 Compared to Example 1, the half width and dislocation density of the X-ray diffraction peak were small, that is, the dislocation density was low and the crystallinity was high because the main surface of the substrate was etched. This is presumably because the work-affected layer and / or the surface oxide layer on the surface and / or the dirt adhering to the main surface of the substrate was removed and good crystal growth was achieved.
- Example 3 a GaN free-standing substrate having a diameter of 2 inches (5.08 cm) grown by the facet growth method described in Japanese Patent Application Laid-Open No. 2003-183100 was prepared as the substrate 10. .
- This GaN free-standing substrate includes a main crystal region 10k and a polarity inversion crystal region 10h whose polarity in the [0001] direction is inverted with respect to the main crystal region, and the dislocation density of the main crystal region 10k is 1 ⁇ 10 5 cm ⁇ 2.
- the dislocation density in the polarity-inverted crystal region 10h was 5 ⁇ 10 7 cm ⁇ 2 .
- a GaN crystal 20 was grown on the main surface 10m of the GaN free-standing substrate in the same manner as in Example 2.
- the thickness of the GaN crystal was 5 ⁇ m
- the half-value width of the X-ray diffraction peak related to the (0002) plane of the GaN crystal was 100 arcsec, and it had very high crystallinity.
- the dislocation density of the main crystal region 20k of the GaN crystal 20 (the crystal region grown on the main surface 10km of the main crystal region 10k of the substrate 10) is 1 ⁇ 10 5 cm ⁇ 2. It was almost the same as the dislocation density of 10k.
- the dislocation density of the polarity inversion crystal region 20h of the GaN crystal 20 (the crystal region grown on the main surface 10hm of the polarity inversion crystal region 10h of the substrate 10) is 5 ⁇ 10 7 cm ⁇ 2 , and the polarity of the substrate 10 This was equivalent to the dislocation density in the inversion crystal region 10h.
- the 1N KOH aqueous solution was brought into contact with the main surface of the GaN crystal 20, the main surface of the polarity reversal crystal region 20h of the GaN crystal 20 was etched.
- Example 4 Preparation of Substrate
- a GaN free-standing substrate having a diameter of 2 inches (5.08 cm) grown by the facet growth method described in Japanese Patent Application Laid-Open No. 2003-183100 was prepared as the substrate 10.
- This GaN free-standing substrate includes a main crystal region 10k and a polarity-inverted crystal region 10h whose polarity in the [0001] direction is inverted with respect to the main crystal region, and the polarity-inverted crystal region compared to the main surface 10km of the main crystal region 10k.
- the main surface 10 hm of 10 h is recessed with a depth D of 10 ⁇ m.
- Such a dent was formed by holding the main surface 10 m of the GaN free-standing substrate at 800 ° C. for about 2 hours in a nitrogen gas atmosphere containing 25% by volume of hydrogen chloride gas.
- the dislocation density in the main crystal region 10k was 1 ⁇ 10 5 cm ⁇ 2
- the dislocation density in the polarity inversion crystal region 10h was 5 ⁇ 10 7 cm ⁇ 2 .
- a GaN crystal 20 was grown on the main surface 10m of the GaN free-standing substrate in the same manner as in Example 2.
- the thickness of the GaN crystal was 5 ⁇ m, and the half-value width of the X-ray diffraction peak related to the (0002) plane of the GaN crystal was 100 arcsec, which had very high crystallinity.
- the dislocation density of the main crystal region 20k of the GaN crystal 20 (the crystal region grown on the main surface 10km of the main crystal region 10k of the substrate 10) is 1 ⁇ 10 5 cm ⁇ 2. It was almost the same as the dislocation density of 10k.
- the dislocation density of the junction crystal region 20c (located on the main surface 10hm of the polarity reversal crystal region 10h of the substrate 10) where the plurality of main crystal regions 20k of the GaN crystal 20 are joined is 2 ⁇ 10 6 cm ⁇ 2 . Although it was larger than the dislocation density of the main crystal region 20k of the GaN crystal 20, it was smaller than the dislocation density of the polarity reversal crystal region 10h of the substrate 10. In addition, when the 1N KOH aqueous solution was brought into contact with the main surface of the GaN crystal 20, the main surface of the GaN crystal 20 was not etched at all, and the polarity inversion crystal region was not formed in the GaN crystal of this example. all right.
- Example 5 Preparation of Substrate With reference to FIG. 2A, a GaN free-standing substrate having a diameter of 2 inches (5.08 cm) having a (1-100) main surface was prepared as a substrate 10. The dislocation density of this GaN free-standing substrate was 2 ⁇ 10 7 cm ⁇ 2 .
- a GaN crystal 20 was grown on the main surface 10m of the GaN free-standing substrate in the same manner as in Example 2.
- the thickness of the GaN crystal was 5 ⁇ m, and the main surface of the GaN crystal was (1-100) plane as measured by X-ray diffraction. Further, the half-value width of the X-ray diffraction peak related to the (1-100) plane of the GaN crystal was 520 arcsec, and it had high crystallinity.
- the dislocation density of the GaN crystal was 2 ⁇ 10 7 cm ⁇ 2 , which was the same as the dislocation density of the GaN free-standing substrate.
- a substrate 10 is formed on a (0001) main surface of a sapphire substrate (basic substrate 10b) having a diameter of 2 inches (5.08 cm) by a MOCVD method with a Ga 0.8 thickness of 3 ⁇ m.
- a MOCVD method with a Ga 0.8 thickness of 3 ⁇ m.
- an In 0.2 N seed crystal Ga x Al y In 1- xy N seed crystal 10a
- Ga 0.8 In 0.2 N template substrate was grown.
- the dislocation density of the Ga 0.8 In 0.2 N seed crystal of the template substrate was 8 ⁇ 10 9 cm ⁇ 2 .
- a GaN crystal 20 was grown on the main surface 10m of the Ga 0.8 In 0.2 N template substrate in the same manner as in Example 2.
- the thickness of the GaN crystal was 5 ⁇ m.
- the half width of the X-ray diffraction peak related to the (0002) plane of the GaN crystal was 540 arcsec.
- the dislocation density of the GaN crystal was 7 ⁇ 10 6 cm ⁇ 2 , which was lower than the dislocation density of the Ga 0.8 In 0.2 N template substrate.
- a substrate 10 is formed on a (0001) main surface of a sapphire substrate (basic substrate 10b) having a diameter of 2 inches (5.08 cm) by a MOCVD method with a Ga 0.8 thickness of 3 ⁇ m.
- Al 0.2 N seed crystal Ga x Al y In 1- xy N seed crystal 10a
- Ga 0.8 Al 0.2 N template substrate was grown.
- the dislocation density of the Ga 0.8 Al 0.2 N seed crystal of the template substrate was 8 ⁇ 10 9 cm ⁇ 2 .
- a GaN crystal 20 was grown on the main surface 10m of the Ga 0.8 Al 0.2 N template substrate in the same manner as in Example 2.
- the thickness of the GaN crystal was 5 ⁇ m.
- the half width of the X-ray diffraction peak related to the (0002) plane of the GaN crystal was 420 arcsec.
- the dislocation density of the GaN crystal was 5 ⁇ 10 6 cm ⁇ 2 , which was lower than the dislocation density of the Ga 0.8 Al 0.2 N template substrate.
- Example 8 Preparation of Substrate Referring to FIG. 2 (a), a substrate 10 having a diameter of 2 inches (5.08 cm) cut out from a GaN crystal thickly grown on a GaAs substrate described in Japanese Patent Application Laid-Open No. 2000-22212. A GaN free-standing substrate was prepared. Here, the dislocation density of the GaN free-standing substrate is 5 ⁇ 10 6 cm ⁇ 2 , and the arithmetic average roughness Ra defined in JIS B0601 of the main surface 10 m is 100 nm when measured with an AFM (atomic force microscope). That was all.
- AFM atomic force microscope
- the CL emission intensity of the surface layer from the surface to a depth of 2 ⁇ m was weak.
- the surface layer having a depth of 2 ⁇ m from the surface is a work-affected layer formed on the surface layer of the GaN free-standing substrate when being cut out from the GaN crystal.
- the main surface of the substrate was etched.
- a GaN crystal 20 was grown on the main surface 10m of the GaN free-standing substrate in the same manner as in Example 2.
- the thickness of the GaN crystal was 5 ⁇ m.
- the half width of the X-ray diffraction peak related to the (0002) plane of the GaN crystal was 420 arcsec.
- the dislocation density of the GaN crystal was 3 ⁇ 10 6 cm ⁇ 2 , which was low and good compared to the dislocation density of the GaN free-standing substrate.
- the arithmetic average roughness Ra of the main surface of the GaN crystal is 10 nm or less, and a surface layer having a low CL emission intensity was not observed at the interface between the GaN free-standing substrate and the GaN crystal grown on the main surface. That is, it can be understood that the work-affected layer was removed by etching the main surface of the GaN free-standing substrate before the growth of the GaN crystal.
- MOCVD is used on the main surface of GaN crystal substrate 30 on which GaN crystal 20 having a thickness of 5 ⁇ m is grown on a GaN free-standing substrate (substrate 10).
- an LED light emitting diode
- TMG trimethylgallium
- TMI trimethylindium
- TMA trimethylaluminum
- ammonia was used as the nitrogen material
- monosilane was used as the n-type dopant material
- CP 2 Mg bis (cyclopentadienyl) magnesium
- an n-type GaN layer 51 having a thickness of 2 ⁇ m is formed as a plurality of group III nitride crystal layers forming the LED structure 55 by MOCVD.
- 88 nm thick MQW (multiple quantum well) light-emitting layers 52 (7 layers of In 0.01 Ga 0.99 N barrier layers 52b alternately arranged in each layer and 6 layers of In 0.14 Ga 0.86 of 3 nm thickness) N-well layer 52w), p-type Al 0.18 Ga 0.82 N electron blocking layer 53 having a thickness of 20 nm and p-type GaN contact layer 54 having a thickness of 50 nm were successively grown.
- a semitransparent ohmic electrode composed of Ni (5 nm) / Au (10 nm) having a vertical width of 400 ⁇ m, a horizontal width of 400 ⁇ m, and a thickness of 15 nm was formed as the p-side electrode 56 by vacuum deposition.
- an n-side electrode 57 is formed by a vacuum vapor deposition method with a vertical width of 400 ⁇ m ⁇ horizontal width of 400 ⁇ m of Ti (20 nm) / Al (300 nm).
- An ohmic electrode having a thickness of 320 nm was formed.
- the LED was completed by making chips into a vertical width of 500 ⁇ m ⁇ a horizontal width of 500 ⁇ m.
- the LED thus obtained had an emission wavelength of 420 nm, and the emission intensity when a current of 20 mA was applied was 4 mW to 5 mW.
- a GaN free-standing substrate was prepared.
- the dislocation density of the GaN free-standing substrate is 5 ⁇ 10 6 cm ⁇ 2
- the arithmetic average roughness Ra defined in JIS B0601 of the main surface 10 m is 100 nm when measured with an AFM (atomic force microscope). That was all.
- the CL emission intensity of the surface layer from the surface to a depth of 2 ⁇ m was weak.
- the surface layer having a depth of 2 ⁇ m from the surface is a work-affected layer formed on the surface layer of the GaN free-standing substrate when being cut out from the GaN crystal.
- the main surface of the substrate was polished.
- polishing the main surface of the substrate After polishing the main surface 10 m of the GaN free-standing substrate (substrate 10) with diamond abrasive grains having an average particle size of 0.1 ⁇ m, colloidal silica abrasive particles having an average particle size of 0.02 ⁇ m are further polished. Used for fine polishing. On the main surface of the polished GaN free-standing substrate, the arithmetic average roughness Ra was 10 nm or less, and a surface layer having a weak CL emission intensity was not observed. That is, it can be seen that the work-affected layer was removed by polishing the main surface of the GaN free-standing substrate.
- an n-type GaN layer 51 having a thickness of 2 ⁇ m
- an MQW (multiple quantum well) light emitting layer 52 having a thickness of 88 nm (7 layers of In 0.01 Ga 0.99 N barriers having a thickness of 7 nm alternately arranged for each layer)
- a p-type Al 0.18 Ga 0.82 N electron blocking layer 53 having a thickness of 20 nm
- a p-type GaN contact layer 54 having a thickness of 50 nm. Grown sequentially.
- a semitransparent ohmic electrode made of Ni (5 nm) / Au (10 nm) having a vertical width of 400 ⁇ m, a horizontal width of 400 ⁇ m, and a thickness of 15 nm was formed as a p-side electrode 56 by vacuum deposition.
- a vertical width of 400 ⁇ m ⁇ width of 400 ⁇ m ⁇ thickness of 320 nm made of Ti (20 nm) / Al (300 nm) is formed by vacuum deposition.
- An ohmic electrode was formed.
- the LED was completed by making chips into a vertical width of 500 ⁇ m ⁇ a horizontal width of 500 ⁇ m.
- the LED thus obtained had an emission wavelength of 420 nm, an emission intensity of 4 mW to 5 mW when a current of 20 mA was applied, and had the same characteristics as the LED of Example 8.
- Example 8 As is clear from the comparison between Example 8 and Reference Example 1, when the light emitting device is manufactured, the removal of the work-affected layer on the main surface of the substrate is replaced with the polishing of the main surface of the substrate. It has been found that a light-emitting device having an equivalent emission wavelength and emission intensity can be obtained even by etching and crystal growth. That is, in the manufacture of a light emitting device, the removal of the work-affected layer on the main surface of the substrate, the etching of the main surface of the substrate, and the crystal growth can be omitted, thereby omitting the polishing step of the main surface of the substrate with high running cost did it.
- Example 9 Preparation of Substrate With reference to FIG. 2A, 1110 GaN template substrates (substrate 10) similar to those in Example 1 were prepared. Referring to FIG. 5, in a carbon crucible A (crystal growth vessel 1A) having an inner diameter of 6 cm and a height of 5 cm, one GaN template substrate (substrate 10), metal Ga having a purity of 99.9999% by mass, was placed in an amount of 85 g. Thirty-seven crucibles A (crystal growth vessel 1A) containing metal Ga and one GaN template substrate were prepared. Referring to FIG. 6, 37 GaN template substrates (substrate 10) are planar as shown in FIG.
- a carbon crucible B (crystal growth vessel 1B) having an inner diameter of 45 cm and a height of 5 cm. And 470 g of metal Ga having a purity of 99.9999% by mass. 29 crucibles B (crystal growth vessel 1B) containing metal Ga and 37 GaN template substrates were prepared.
- 29 crucibles B (crystal growth vessel 1B) containing metal Ga and 37 GaN template substrates are arranged in the crystal growth chamber 110 in the vertical direction (that is, crucibles). 29 layers of B were stacked).
- a carbon flat plate 130 was placed on the uppermost crucible B.
- crucibles A (crystal growth vessel 1A) containing 37 metal Ga and one GaN template substrate are arranged side by side so as to be hexagonally dense in a horizontal direction as shown in FIG. .
- 29 crucibles B constituting 29 stages and 17 crucibles A constituting one stage were arranged in the crystal growth chamber 110.
- nitrogen gas having a purity of 99.999% by mass is supplied into the crystal growth chamber 110, and crucible A (crystal growth vessel 1A) and crucible B (crystal growth vessel 1B) are supplied. ) was maintained at 1100 ° C. and pressurized from 30 atm (3.04 MPa) to 1950 atm (197.5 MPa) over 2 hours. Next, crucible A and crucible B were held for 10 hours under a nitrogen atmosphere of 1950 atm and 1100 ° C.
- GaN crystals grew. Of the 1110 GaN crystals grown, the thickest GaN crystal had a thickness of 7 ⁇ m, and the thinnest GaN crystal had a thickness of 2 ⁇ m.
- the half width of the X-ray diffraction peak relating to the (0002) plane of 30 GaN crystals extracted from 1110 GaN crystals was 470 arcsec at the maximum and 280 arcsec at the minimum, and had high crystallinity.
- the dislocation density of 30 GaN crystals is 8 ⁇ 10 6 cm ⁇ 2 at the maximum and 3 ⁇ 10 6 cm ⁇ 2 at the minimum, and the dislocation density of the GaN seed crystal of the substrate and the GaN crystal of Example 1 is the same. It was lower than that.
- the FWHM and dislocation density of the X-ray diffraction peak were small for all the extracted GaN crystals compared to Example 1, that is, the dislocation density was low and the crystallinity was high. This is probably because the work-affected layer and / or the surface oxide layer on the main surface of the substrate and / or the dirt adhering to the main surface of the substrate were removed by etching the main surface, and good crystal growth was achieved.
- 1, 1A, 1B crystal growth vessel 3 Ga melt, nitrogen dissolved in the 5 Ga melt 7 solution, 10 substrate, 10a Ga x Al y In 1 -xy N seed crystal, 10b underlying substrate, by 10e etching Surface layer to be removed, 10h, 20h Polarity reversal crystal region, 10k, 20k main crystal region, 10m, 10hm, 10km main surface, 10v, 10w recess, 20 GaN crystal, 20c junction crystal region, 30 GaN crystal substrate, 51 n Type GaN layer, 52 MQW light emitting layer, 52b In 0.01 Ga 0.99 N barrier layer, 52 w In 0.14 Ga 0.86 N well layer, 53 p type Al 0.18 Ga 0.82 N electron blocking layer, 54 p type GaN contact layer, 55 LED structure, 56 p-side electrode, 57 n-side electrode, 110 crystal growth chamber, 110e gas supply port, 120 heater, 130 flat plate.
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Abstract
Description
図1を参照して、本発明にかかるGaN結晶の成長方法の一実施形態は、一主面10mを有する基板10であって、その主面10mを有するGaxAlyIn1-x-yN(0<x、0≦y、x+y≦1、以下同じ)種結晶10aを含む基板10を準備する工程と、基板10の主面10mに、Ga融液3に窒素を溶解(Ga融液への窒素の溶解5)させた溶液7を接触させて、800℃以上1500℃以下の雰囲気温度および500気圧(50.7MPa)以上2000気圧未満(202.6MPa)の雰囲気圧力下で、主面10m上にGaN結晶20を成長させる工程と、を備える。
図2を参照して、本発明にかかるGaN結晶の成長方法の他の実施形態は、実施形態1において、基板を準備する工程(図2(a))の後、GaN結晶を成長させる工程(図2(c))の前に、基板10の主面10mをエッチングする工程(図2(b))をさらに備える。
図3を参照して、本発明にかかるGaN結晶の成長方法のさらに他の実施形態は、実施形態1または実施形態2において、基板10は、GaxAlyIn1-x-yN種結晶10aが主結晶領域10kと主結晶領域10kに対して[0001]方向の極性が反転した極性反転結晶領域10hとを含む。かかる基板10は、実施形態1または実施形態2の基板に比べて、主結晶領域の転位密度がより低減されているため、かかる基板10の主結晶領域10kの主面10km上に転位密度がより低く結晶性がより高いGaN結晶20を成長させることができる。
図4を参照して、本発明にかかるGaN結晶の成長方法のさらに他の実施形態は、実施形態1または実施形態2において、基板10は、GaxAlyIn1-x-yN種結晶10aが主結晶領域10kと主結晶領域10kに対して[0001]方向の極性が反転した極性反転結晶領域10hとを含み、主結晶領域10kの主面10kmに比べて極性反転結晶領域10hの主面10hmが10μm以上の深さDで凹んでいる。
図1~図8を参照して、本発明にかかるGaN結晶の成長方法のさらに他の実施形態は、実施形態1~実施形態4における基板を準備する工程において、基板10を複数準備し、1つ以上の基板10を収容した結晶成長容器1,1A,1Bを複数準備し、結晶成長室110内に複数の結晶成長容器1,1A,1Bを水平方向および垂直方向の少なくともいずれかの方向に並べて配置する。
1.基板の準備
図1(a)を参照して、基板10として、直径2インチ(5.08cm)のサファイア基板(基礎基板10b)の(0001)主面上にMOCVD法により厚さ3μmのGaN種結晶(GaxAlyIn1-x-yN種結晶10a)を成長させたGaNテンプレート基板を準備した。このGaNテンプレート基板のGaN種結晶の転位密度は、CL(カソードルミネッセンス)法により測定したところ、1×109cm-2であった。
図1(b)を参照して、結晶成長室(図示せず)内に配置された内径6cm×高さ5cmのカーボン製の坩堝(結晶成長容器1)内に、上記GaNテンプレート基板(基板10)および純度99.9999質量%の金属Gaを85g配置した。
1.基板の準備
図2(a)を参照して、実施例1と同様のGaNテンプレート基板(基板10)を準備した。
図2(b)を参照して、結晶成長室(図示せず)内に配置された内径6cm×高さ5cmのカーボン製の坩堝(結晶成長容器1)内に、上記GaNテンプレート基板(基板10)および純度99.9999質量%の金属Gaを85g配置した。
次に、図2(b)を参照して、結晶成長室(図示せず)内に純度99.999質量%の窒素ガスを供給して、坩堝(結晶成長容器1)を、1100℃に保持して2時間かけて30気圧(3.04MPa)から1950気圧(197.5MPa)まで加圧した。次いで、1950気圧および1100℃の窒素雰囲気下で坩堝を10時間保持した。
1.基板の準備
図3(a)を参照して、基板10として、特開2003-183100号公報に記載されたファセット成長法により成長させた直径2インチ(5.08cm)のGaN自立基板を準備した。このGaN自立基板は、主結晶領域10kと主結晶領域に対して[0001]方向の極性が反転した極性反転結晶領域10hとを含み、主結晶領域10kの転位密度は1×105cm-2であり、極性反転結晶領域10hの転位密度は5×107cm-2であった。
図3(b)を参照して、実施例2と同様にして、GaN自立基板の主面10mのエッチングを行なった。
図3(c)を参照して、実施例2と同様にして、GaN自立基板の主面10m上にGaN結晶20を成長させた。GaN結晶の厚さは5μmであり、GaN結晶の(0002)面に関するX線回折ピークの半値幅は100arcsecであり、非常に高い結晶性を有していた。また、GaN結晶20の主結晶領域20k(基板10の主結晶領域10kの主面10km上に成長した結晶領域)の転位密度は、1×105cm-2であり、基板10の主結晶領域10kの転位密度とほぼ同じであった。また、GaN結晶20の極性反転結晶領域20h(基板10の極性反転結晶領域10hの主面10hm上に成長した結晶領域)の転位密度は、5×107cm-2であり、基板10の極性反転結晶領域10hの転位密度と同等であった。なお、GaN結晶20の主面に1NのKOH水溶液を接触させたところ、GaN結晶20の極性反転結晶領域20hの主面がエッチングされた。
1.基板の準備
図4(a)を参照して、基板10として、特開2003-183100号公報に記載されたファセット成長法により成長させた直径2インチ(5.08cm)のGaN自立基板を準備した。このGaN自立基板は、主結晶領域10kと主結晶領域に対して[0001]方向の極性が反転した極性反転結晶領域10hとを含み、主結晶領域10kの主面10kmに比べて極性反転結晶領域10hの主面10hmが10μmの深さDで凹んでいる。かかる凹みは、GaN自立基板の主面10mを800℃に加熱しながら、25体積%の塩化水素ガスを含む窒素ガス雰囲気中で、約2時間保持することにより形成した。主結晶領域10kの転位密度は1×105cm-2であり、極性反転結晶領域10hの転位密度は5×107cm-2であった。
図4(b)を参照して、実施例2と同様にして、GaN自立基板の主面10mのエッチングを行なった。
図4(c)を参照して、実施例2と同様にして、GaN自立基板の主面10m上にGaN結晶20を成長させた。GaN結晶の厚さは5μmであり、GaN結晶の(0002)面に関するX線回折ピークの半値幅は100arcsecであり、非常高い結晶性を有していた。また、GaN結晶20の主結晶領域20k(基板10の主結晶領域10kの主面10km上に成長した結晶領域)の転位密度は、1×105cm-2であり、基板10の主結晶領域10kの転位密度とほぼ同じであった。また、GaN結晶20の複数の主結晶領域20kが接合する接合結晶領域20c(基板10の極性反転結晶領域10hの主面10hm上に位置する)の転位密度は、2×106cm-2であり、GaN結晶20の主結晶領域20kの転位密度に比べて大きかったものの、基板10の極性反転結晶領域10hの転位密度に比べて小さかった。また、GaN結晶20の主面に1NのKOH水溶液を接触させたところ、GaN結晶20の主面は全くエッチングされず、本実施例のGaN結晶には極性反転結晶領域が形成されていないことがわかった。
1.基板の準備
図2(a)を参照して、基板10として、(1-100)主面を有する直径2インチ(5.08cm)のGaN自立基板を準備した。このGaN自立基板の転位密度は2×107cm-2であった。
図2(b)を参照して、実施例2と同様にして、GaN自立基板の主面10mのエッチングを行なった。
図2(c)を参照して、実施例2と同様にして、GaN自立基板の主面10m上にGaN結晶20を成長させた。GaN結晶の厚さは5μmであり、GaN結晶の主面は、X線回折法により測定したところ、(1-100)面であった。また、GaN結晶の(1-100)面に関するX線回折ピークの半値幅は520arcsecであり、高い結晶性を有していた。また、GaN結晶の転位密度は、2×107cm-2であり、GaN自立基板の
転位密度と同じであった。
1.基板の準備
図2(a)を参照して、基板10として、直径2インチ(5.08cm)のサファイア基板(基礎基板10b)の(0001)主面上にMOCVD法により厚さ3μmのGa0.8In0.2N種結晶(GaxAlyIn1-x-yN種結晶10a)を成長させたGa0.8In0.2Nテンプレート基板を準備した。ここで、テンプレート基板のGa0.8In0.2N種結晶の転位密度は、8×109cm-2であった。
図2(b)を参照して、実施例2と同様にして、Ga0.8In0.2Nテンプレート基板の主面10mのエッチングを行なった。
図2(c)を参照して、実施例2と同様にして、Ga0.8In0.2Nテンプレート基板の主面10m上にGaN結晶20を成長させた。GaN結晶の厚さは5μmであった。また、GaN結晶の(0002)面に関するX線回折ピークの半値幅は540arcsecであった。また、GaN結晶の転位密度は、7×106cm-2であり、Ga0.8In0.2Nテンプレート基板の転位密度に比べて低くなっていた。
1.基板の準備
図2(a)を参照して、基板10として、直径2インチ(5.08cm)のサファイア基板(基礎基板10b)の(0001)主面上にMOCVD法により厚さ3μmのGa0.8Al0.2N種結晶(GaxAlyIn1-x-yN種結晶10a)を成長させたGa0.8Al0.2Nテンプレート基板を準備した。ここで、テンプレート基板のGa0.8Al0.2N種結晶の転位密度は、8×109cm-2であった。
図2(b)を参照して、実施例2と同様にして、Ga0.8Al0.2Nテンプレート基板の主面10mのエッチングを行なった。
図2(c)を参照して、実施例2と同様にして、Ga0.8Al0.2Nテンプレート基板の主面10m上にGaN結晶20を成長させた。GaN結晶の厚さは5μmであった。また、GaN結晶の(0002)面に関するX線回折ピークの半値幅は420arcsecであった。また、GaN結晶の転位密度は、5×106cm-2であり、Ga0.8Al0.2Nテンプレート基板の転位密度に比べて低くなっていた。
1.基板の準備
図2(a)を参照して、基板10として、特開2000-22212号公報に記載されたGaAs基板上に厚く成長させたGaN結晶から切り出された直径2インチ(5.08cm)のGaN自立基板を準備した。ここで、GaN自立基板の転位密度は5×106cm-2であり、主面10mのJIS B0601に規定される算術平均粗さRaは、AFM(原子間力顕微鏡)で測定したところ、100nm以上であった。また、このGaN自立基板は、その断面をSEM観察およびCL観察したところ、表面から深さ2μmまでの表面層のCL発光強度が弱かった。この表面から深さ2μmまでの表面層は、GaN結晶から切り出す際にGaN自立基板の表面層に形成された加工変質層である。かかる加工変質層を除去するために、基板の主面のエッチングを行なった。
図2(b)を参照して、実施例2と同様にして、GaN自立基板の主面10mのエッチングを行なった。
図2(c)を参照して、実施例2と同様にして、GaN自立基板の主面10m上にGaN結晶20を成長させた。GaN結晶の厚さは5μmであった。また、GaN結晶の(0002)面に関するX線回折ピークの半値幅は420arcsecであった。また、GaN結晶の転位密度は3×106cm-2であり、GaN自立基板の転位密度に比べて低く良好であった。また、GaN結晶の主面の算術平均粗さRaは10nm以下であり、GaN自立基板とその主面上に成長したGaN結晶との界面にはCL発光強度の弱い表面層は観察されなかった。すなわち、GaN結晶の成長前にGaN自立基板の主面をエッチングすることにより、加工変質層が除去されたことがわかる。
図9を参照して、GaN自立基板(基板10)上に厚さ5μmのGaN結晶20を成長させたGaN結晶基板30のGaN結晶20側の主面上に、MOCVD法を用いて、LED構造55を形成して発光デバイスたるLED(発光ダイオード)を作製した。ここで、LED構造55を形成する複数のIII族窒化物結晶層を成長させるために、III族原料としては、トリメチルガリウム(TMG)、トリメチルインジウム(TMI)および/またはトリメチルアルミニウム(TMA)を用い、窒素原料としてはアンモニアを用い、n型ドーパント原料としてはモノシランを用い、p型ドーパント原料としてはビス(シクロペンタジエニル)マグネシウム(CP2Mg)を用いた。
なお、実施例8と比較するために、以下の方法で典型的なLEDを作製して、その発光波長および発光強度を測定した。
図2(a)を参照して、基板10として、特開2000-22212号公報に記載されたGaAs基板上に厚く成長させたGaN結晶から切り出された直径2インチ(5.08cm)のGaN自立基板を準備した。ここで、GaN自立基板の転位密度は5×106cm-2であり、主面10mのJIS B0601に規定される算術平均粗さRaは、AFM(原子間力顕微鏡)で測定したところ、100nm以上であった。また、このGaN自立基板は、その断面をSEM観察およびCL観察したところ、表面から深さ2μmまでの表面層のCL発光強度が弱かった。この表面から深さ2μmまでの表面層は、GaN結晶から切り出す際にGaN自立基板の表面層に形成された加工変質層である。かかる加工変質層を除去するために、基板の主面の研磨を行なった。
GaN自立基板(基板10)の主面10mを、平均粒径0.1μmのダイヤモンド砥粒を用いて研磨した後、さらに、平均粒径0.02μmのコロイダルシリカ砥粒を用いて微細研磨した。研磨後のGaN自立基板の主面において、その算術平均粗さRaは10nm以下であり、CL発光強度の弱い表面層は観察されなかった。すなわち、GaN自立基板の主面を研磨することにより、加工変質層が除去されたことがわかる。
図10を参照して、GaN自立基板(基板10)の一方の主面上に、実施例8と同様にして、MOCVD法により、LED構造55を形成する複数のIII族窒化物結晶層として、厚さ2μmのn型GaN層51、厚さ88nmのMQW(多重量子井戸)発光層52(1層毎に交互に配置された7層の厚さ10nmのIn0.01Ga0.99N障壁層52bと6層の厚さ3nmのIn0.14Ga0.86N井戸層52wを有する)、厚さ20nmのp型Al0.18Ga0.82N電子ブロック層53および厚さ50nmのp型GaNコンタクト層54を、順次成長させた。さらに、p型GaNコンタクト層54上に、真空蒸着法により、p側電極56としてNi(5nm)/Au(10nm)からなる縦幅400μm×横幅400μm×厚さ15nmの半透明オーミック電極を形成した。また、GaN自立基板(基板10)の他方の主面上に、n側電極57として、真空蒸着法により、Ti(20nm)/Al(300nm)からなる縦幅400μm×横幅400μm×厚さ320nmのオーミック電極を形成した。次いで、縦幅500μm×横幅500μmにチップ化してLEDを完成させた。
1.基板の準備
図2(a)を参照して、実施例1と同様のGaNテンプレート基板(基板10)を1110枚準備した。図5を参照して、内径6cm×高さ5cmのカーボン製の坩堝A(結晶成長容器1A)内に、1枚の上記GaNテンプレート基板(基板10)と純度99.9999質量%の金属Gaとを85g配置した。金属Gaおよび1枚のGaNテンプレート基板を収容した坩堝A(結晶成長容器1A)を37個準備した。また、図6を参照して、内径45cm×高さ5cmのカーボン製の坩堝B(結晶成長容器1B)内に、37枚の上記GaNテンプレート基板(基板10)を図6に示すように平面的に六方稠密になるように並べて配置し、また純度99.9999質量%の金属Gaを470g配置した。金属Gaおよび37枚のGaNテンプレート基板を収容した坩堝B(結晶成長容器1B)を29個準備した。
次に、結晶成長室110内に純度99.999質量%の窒素ガスを供給して、坩堝Aおよび坩堝Bを、30気圧(3.04MPa)に保持して3時間かけて室温(25℃)から1100℃まで加熱した。このとき、坩堝Aおよび坩堝B内に配置された金属Gaが融解してGa融液3となり、Ga融液3への窒素の溶解5により得られた溶液7が基板10の主面10mに接触している。しかし、この条件においては、Ga融液への窒素の溶解が少ないため、GaN結晶を成長させることなく、GaNテンプレート基板のGaN種結晶の主面10mがエッチングされる。
次に、図8を参照して、結晶成長室110内に純度99.999質量%の窒素ガスを供給して、坩堝A(結晶成長容器1A)および坩堝B(結晶成長容器1B)を、1100℃に保持して2時間かけて30気圧(3.04MPa)から1950気圧(197.5MPa)まで加圧した。次いで、1950気圧および1100℃の窒素雰囲気下で坩堝Aおよび坩堝Bを10時間保持した。
Claims (6)
- 一主面(10m)を有する基板(10)であって、前記主面(10m)を有するGaxAlyIn1-x-yN(0<x、0≦y、x+y≦1)種結晶(10a)を含む前記基板(10)を準備する工程と、
前記基板(10)の前記主面(10m)に、Ga融液(3)に窒素を溶解させた溶液(7)を接触させて、800℃以上1500℃以下の雰囲気温度および500気圧以上2000気圧未満の雰囲気圧力下で、前記主面(10m)上にGaN結晶(20)を成長させる工程と、を備えるGaN結晶の成長方法。 - 前記基板(10)を準備する工程の後、前記GaN結晶(20)を成長させる工程の前に、前記基板(10)の前記主面(10m)をエッチングする工程を、さらに備える請求の範囲第1項に記載のGaN結晶の成長方法。
- 前記基板(10)の前記主面(10m)をエッチングする工程は、前記基板(10)の前記主面(10m)に、Ga融液(3)に窒素を溶解させた溶液(7)を接触させて、800℃以上1500℃以下の雰囲気温度および1気圧以上500気圧未満の雰囲気圧力下で行なう請求の範囲第2項に記載のGaN結晶の成長方法。
- 前記基板(10)は、前記GaxAlyIn1-x-yN種結晶(10a)が主結晶領域(10k)と前記主結晶領域(10k)に対して[0001]方向の極性が反転した極性反転結晶領域(10h)とを含む請求の範囲第1項に記載のGaN結晶の成長方法。
- 前記基板(10)は、前記主結晶領域(10k)の主面(10km)に比べて前記極性反転結晶領域(10h)の主面(10hm)が10μm以上の深さで凹んでいる請求の範囲第4項に記載のGaN結晶の成長方法。
- 前記基板(10)を準備する工程において、前記基板(10)を複数準備し、1つ以上の前記基板(10)を収容した結晶成長容器(1,1A,1B)を複数準備し、結晶成長室(110)内に複数の前記結晶成長容器(1,1A,1B)を水平方向および垂直方向の少なくともいずれかの方向に並べて配置する請求の範囲第1項に記載のGaN結晶の成長方法。
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