JP2012039150A - Method for growing group iii nitride semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for growing group III nitride semiconductor capable of reducing the number of surface defects of the group III nitride semiconductor.SOLUTION: In a growth process S1, a gas G1 containing an ammonia and group III organic metal matter is supplied into a growth furnace 15 of a vapor phase growth apparatus 11 to grow a group III nitride semiconductor of GaN etc. In a process S2, the group III organic metal matter is stopped from being supplied into the vapor phase growth apparatus 11 at the time t1 to finish the growth of the group III nitride semiconductor. In a process S3, the temperature of the vapor phase growth apparatus 11 is changed in the term after the time t1 while supplying a gas containing ammonia, so that the temperature of a reactor 15 of the vapor phase growth apparatus 11 becomes a temperature Temp 2 lower than the temperature Temp 1 of the time t1 at the time t2. A supply of ammonia is increased in at least either of the growth term Ta of the group III nitride semiconductor or the term Tb of temperature change of the vapor phase growth apparatus.

Description

  The present invention relates to a method for growing a group III nitride semiconductor and a method for manufacturing a group III nitride semiconductor device.

  Non-Patent Document 1 describes the leakage current at the Schottky interface between GaN and AlGaN. According to this document, a donor due to surface defects thins the barrier, and a transport process by tunneling is caused by the thin barrier. As a result, the leakage current at the Schottky interface between GaN and AlGaN is large.

APPLIEDPHYSICS LETTERS, Vol.84, 14 June 2004, pp.4884-4886

  In a GaN Schottky barrier diode having a Schottky junction to n-type gallium nitride and a high electron mobility transistor having a gate electrode provided on an AlGaN electron barrier layer, a defect donor is present on the surface according to the inventors' knowledge. When present, there is much leakage current due to the Schottky junction. Further, it is considered that the contact resistance increases in a nitride light emitting device such as a light emitting diode or a semiconductor laser having an ohmic electrode that forms a junction with the p-type contact layer. Therefore, it is necessary to reduce the defect donors on the epi surface. However, the above Non-Patent Document 1 does not describe reducing the defective donors on the surface of the epitaxial layer of the group III nitride.

  An object of the present invention is to provide a method for growing a group III nitride semiconductor and a method for manufacturing a group III nitride semiconductor device capable of reducing the number of surface defects of the group III nitride.

  A method for growing a group III nitride semiconductor according to the present invention, the method comprising: (a) supplying a gas containing ammonia and a group III organometallic substance to a vapor phase growth apparatus, (B) stopping the supply of the group III organometallic material to the vapor phase growth apparatus at a first time and terminating the growth of the group III nitride semiconductor; (c) ) A gas containing ammonia so that the temperature of the vapor phase growth apparatus at the second time after the first time becomes a temperature Temp2 lower than the temperature Temp1 of the vapor phase growth apparatus at the first time And a step of changing the temperature of the vapor phase growth apparatus during a period after the first time while supplying a gas, and a growth period of the group III nitride semiconductor and a temperature change period of the vapor phase growth apparatus. At least one period During the supply amount of the ammonia is increased.

  According to this method, since the supply amount of ammonia is increased at least before or after the supply of the group III organometallic material to the vapor phase growth apparatus is stopped, the growth of the group III nitride semiconductor is completed. Thereafter, during the period in which the temperature of the vapor phase growth apparatus is lowered to the temperature Temp2, the number of defective donors generated in the group III nitride semiconductor is reduced.

  In the method for growing a group III nitride semiconductor according to the present invention, the increase in the supply amount of the ammonia can be started during the growth period of the group III nitride semiconductor. According to this method, since the process proceeds to the process of the change period while supplying more ammonia than the initial supply amount of ammonia during the growth period, it is possible to reduce the occurrence of defective donors in the group III nitride semiconductor.

  In the method for growing a group III nitride semiconductor according to the present invention, the increase in the supply amount of ammonia can be started during a temperature change period of the vapor phase growth apparatus. According to this method, during the change period, more ammonia is supplied than the ammonia supply amount at the end of the growth period, so that the number of defective donors generated in the group III nitride semiconductor is reduced.

  A method of growing a group III nitride semiconductor according to the present invention, the method comprising: (a) supplying a gas containing hydrogen, ammonia, and a group III organometallic substance to a vapor phase growth apparatus; A step of growing a semiconductor, and (b) stopping supplying the group III organometallic material to the vapor phase growth apparatus at a first time, and ending the growth of the group III nitride semiconductor, (C) At a second time after the first time, the ammonia is added so that the temperature of the vapor phase growth apparatus becomes a temperature Temp2 lower than the temperature Temp1 of the vapor phase growth apparatus at the first time. A step of changing the temperature of the vapor phase growth apparatus during a period after the first time while supplying a gas containing the gas, and a growth period of the group III nitride semiconductor and a change of the temperature of the vapor phase growth apparatus At least one of the period Supply amount of the hydrogen is decreased during the period.

  According to this method, since the supply amount of hydrogen is reduced at least either before or after stopping the supply of the group III organometallic material to the vapor phase growth apparatus, the growth of the group III nitride semiconductor is prevented. It is possible to reduce the occurrence of defective donors in the group III nitride semiconductor during the period of changing the temperature of the vapor phase growth apparatus to the temperature Temp2 after completion.

  In the method according to the present invention, the reduction of the hydrogen supply amount can be started during the growth period of the group III nitride semiconductor. According to this method, since the process proceeds to the process of the change period while supplying a smaller amount of hydrogen than the initial supply of hydrogen during the growth period, it is possible to reduce the occurrence of defective donors in the group III nitride semiconductor.

  In the method according to the present invention, the reduction of the hydrogen supply amount can be started during a temperature change period of the vapor phase growth apparatus. According to this method, since a smaller amount of hydrogen is supplied during the change period than the hydrogen supply amount at the end of the growth period, occurrence of defective donors in the group III nitride semiconductor can be reduced.

  In the method according to the present invention, the reduced hydrogen supply can be substantially zero. According to this method, the surface of the grown group III nitride semiconductor is not exposed to a large amount of hydrogen.

  In the method according to the present invention, it is preferable that the supply amount of hydrogen is reduced and nitrogen is supplied to the vapor phase growth apparatus. According to this method, the nitrogen partial pressure of the vapor phase growth apparatus can be increased. Further, the increase in the nitrogen supply amount along with the decrease in the hydrogen supply amount can reduce the change in the pressure of the vapor phase growth apparatus, and the gas flow turbulence caused by the change in the total flow rate can be reduced.

  In the method according to the present invention, the supply amount of ammonia can be increased while the supply amount of hydrogen is decreased. According to this method, the nitrogen partial pressure of the vapor phase growth apparatus can be increased. In addition, the change in the pressure of the vapor phase growth apparatus can be reduced by reducing the supply amount of hydrogen and the increase in the supply amount of ammonia, and the turbulence of the gas flow due to the change in the total flow rate can be reduced.

  A method for growing a group III nitride semiconductor according to the present invention, the method comprising: (a) supplying a gas containing ammonia and a group III organometallic substance to a vapor phase growth apparatus, (B) stopping the supply of the group III organometallic material to the vapor phase growth apparatus at a first time and terminating the growth of the group III nitride semiconductor; (c) ) A gas containing ammonia so that the temperature of the vapor phase growth apparatus at the second time after the first time becomes a temperature Temp2 lower than the temperature Temp1 of the vapor phase growth apparatus at the first time And a step of changing the temperature of the vapor phase growth apparatus during a period after the first time while supplying a gas, and a growth period of the group III nitride semiconductor and a temperature change period of the vapor phase growth apparatus. At least one period During the nitrogen is increased from the first supply amount to the second supply amount.

  According to this method, since the supply amount of nitrogen is increased at least either before or after stopping the supply of the group III organometallic material to the vapor phase growth apparatus, the growth of the group III nitride semiconductor is increased. During the period when the temperature of the vapor phase growth apparatus is changed to the temperature Temp2 after completion, the number of defective donors generated in the group III nitride semiconductor can be reduced.

  In the method according to the present invention, the increase in the supply amount of nitrogen can be started during the growth period of the group III nitride semiconductor. According to this method, since the process proceeds to the process of the change period while supplying a larger amount of nitrogen than the initial supply of nitrogen during the growth period, it is possible to reduce defective donors generated in the group III nitride semiconductor.

  In the method according to the present invention, the increase of the nitrogen supply amount can be started during a temperature change period of the vapor phase growth apparatus. According to this method, since a larger amount of nitrogen is supplied during the change period than the amount of nitrogen supplied at the end of the growth period, the number of defective donors generated in the group III nitride semiconductor can be reduced.

  In the method according to the present invention, the first supply amount of the nitrogen can be substantially zero.

  A method for growing a group III nitride semiconductor according to the present invention, the method comprising: (a) supplying a gas containing ammonia and a group III organometallic substance to a vapor phase growth apparatus, (B) stopping the supply of the group III organometallic material to the vapor phase growth apparatus at a first time and terminating the growth of the group III nitride semiconductor; (c) ) A gas containing ammonia so that the temperature of the vapor phase growth apparatus at the second time after the first time becomes a temperature Temp2 lower than the temperature Temp1 of the vapor phase growth apparatus at the first time And a step of changing the temperature of the vapor phase growth apparatus during a period after the first time while supplying a gas, and a growth period of the group III nitride semiconductor and a temperature change period of the vapor phase growth apparatus. At least one period During the pressure of the vapor phase growth apparatus is increased from the first pressure value to the second pressure value.

  According to this method, since the pressure is increased at least either before or after stopping the supply of the group III organometallic material to the vapor phase growth apparatus, after the growth of the group III nitride semiconductor is completed. During the period of changing the temperature of the vapor phase growth apparatus to the temperature Temp2, the number of defective donors generated in the group III nitride semiconductor can be reduced.

  In the method according to the present invention, the increase in pressure can be initiated during the growth period of the group III nitride semiconductor. According to this method, since the process proceeds to the change period step at a pressure larger than the initial growth pressure during the growth period, the number of defective donors generated in the group III nitride semiconductor can be reduced.

  In the method according to the present invention, the increase in pressure can be initiated during a temperature change period of the vapor phase growth apparatus. According to this method, since the pressure during the change period is larger than the pressure at the end of the growth period, the number of defective donors generated in the group III nitride semiconductor can be reduced.

  A method for growing a group III nitride semiconductor according to the present invention, the method comprising: (a) supplying a gas containing ammonia and a group III organometallic substance to a vapor phase growth apparatus, (B) stopping the supply of the group III organometallic material to the vapor phase growth apparatus at a first time and terminating the growth of the group III nitride semiconductor; (c) ) A gas containing ammonia is used so that the temperature of the vapor phase growth apparatus at the second time after the first time becomes a temperature Temp2 lower than the temperature Temp1 of the vapor phase growth apparatus at the first time. A step of changing the temperature of the vapor phase growth apparatus during the period after the first time while supplying, and during the growth period of the group III nitride semiconductor, the temperature from the temperature Temp3 higher than the temperature Temp1 to the temperature Tem Temperature of the vapor phase growth apparatus is changed to 1.

  According to this method, the temperature is changed from the temperature Temp3 to the temperature Temp1 before the supply of the group III organometallic material to the vapor phase growth apparatus is stopped, and the vapor phase growth apparatus is completed after the growth of the group III nitride semiconductor is completed. Since the temperature is changed from the temperature Temp1 to the temperature Temp2, the number of defective donors generated in the group III nitride semiconductor during the change period can be reduced.

A method for growing a group III nitride semiconductor according to the present invention, the method comprising: (a) supplying a gas containing ammonia and a group III organometallic substance to a vapor phase growth apparatus, (B) stopping the supply of the group III organometallic material to the vapor phase growth apparatus at a first time and terminating the growth of the group III nitride semiconductor; (c) ) A gas containing ammonia so that the temperature of the vapor phase growth apparatus at the second time after the first time becomes a temperature Temp2 lower than the temperature Temp1 of the vapor phase growth apparatus at the first time And changing the temperature of the vapor phase growth apparatus during a period after the first time while supplying at least one of the following (1) to (5):
(1) The supply amount of the ammonia is increased during at least one of the growth period of the group III nitride semiconductor and the temperature change period of the vapor phase growth apparatus.
(2) The supply amount of hydrogen is reduced during at least one of the growth period and the change period.
(3) Nitrogen is increased from the first supply amount to the second supply amount during at least one of the growth period and the change period;
(4) During the growth period of the group III nitride semiconductor, the temperature of the vapor phase growth apparatus is changed from the temperature Temp3 higher than the temperature Temp1 to the temperature Temp1.
(5) During at least one of the growth period and the change period, the pressure of the vapor phase growth apparatus is increased from the first pressure value to the second pressure value.

  According to this method, it is possible to reduce defective donors generated in the group III nitride semiconductor during the change period.

  The invention according to the present invention is a method for producing a group III nitride semiconductor device, the method comprising: (a) growing a group III nitride semiconductor layer according to any one of the above methods; and (b) said step Forming a Schottky electrode on the group III nitride semiconductor layer.

  According to this method, the leakage current of the Schottky junction due to the defective donor on the surface of the group III nitride semiconductor can be reduced. Further, the reduction in the barrier height of the Schottky junction can be reduced. For example, in the Schottky barrier diode, the leakage current of the Schottky electrode is reduced. For example, in a Schottky gate of a high electron mobility transistor, the gate leakage current is reduced.

  The invention according to the present invention is a method of manufacturing a group III nitride semiconductor device, the method comprising: (a) growing a p-type group III nitride semiconductor layer according to any one of the above methods; b) forming an ohmic electrode on the group III nitride semiconductor layer.

  According to this method, the resistance of the ohmic junction due to the defective donor on the surface of the group III nitride semiconductor can be reduced. For example, it is possible to reduce the contact resistance of an electrode that forms an ohmic junction with a p-type group III nitride semiconductor such as a pn junction diode, a pin junction diode, a light emitting diode, or a semiconductor laser.

  In the above method according to the present invention, the group III nitride semiconductor is preferably AlGaN or AlN. According to this method, it is possible to suppress the formation of defective donors on the surface of the group III nitride semiconductor containing aluminum.

  In the above method according to the present invention, the group III nitride semiconductor is preferably n-type GaN. For example, if a Schottky electrode forming a Schottky junction is formed on n-type GaN, the leakage current of the Schottky electrode is reduced.

  In the above method according to the present invention, the group III nitride semiconductor is preferably p-type GaN. According to this method, for example, if an electrode that forms an ohmic junction with p-type GaN is formed, the contact resistance of the electrode is reduced.

  In the above method according to the present invention, the group III nitride semiconductor is preferably i-type GaN. According to this method, it is possible to suppress the formation of defective donors on the surface of i-type GaN. Thereby, the surface leakage current resulting from the defective donor is reduced on the surface of the i-type GaN.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, there is provided a method for growing a group III nitride semiconductor capable of reducing the number of surface defects of the group III nitride. Also provided is a method of fabricating a group III nitride semiconductor device.

FIG. 1A to FIG. 1F are drawings showing a method for growing a group III nitride semiconductor according to the first embodiment. FIG. 2 shows a crystal growth apparatus that can be used to grow a group III nitride semiconductor according to the present embodiment. FIGS. 3A and 3B are flowcharts showing a method of manufacturing the group III nitride semiconductor device according to the first embodiment. 4A to 4F are drawings showing a method for growing a group III nitride semiconductor according to a modification of the first embodiment. FIGS. 5A to 5F are views showing a method for growing a group III nitride semiconductor according to the second embodiment. FIGS. 6A to 6F are views showing a method for growing a group III nitride semiconductor according to a modification of the second embodiment. FIG. 7A to FIG. 7F are drawings showing a method for growing a group III nitride semiconductor of an experimental example. FIGS. 8A to 8F are views showing a method for growing a group III nitride semiconductor according to the third embodiment. FIG. 9A to FIG. 9F are drawings showing a method for growing a group III nitride semiconductor according to a modification of the third embodiment. FIGS. 10A to 10F are views showing a method for growing a group III nitride semiconductor according to a modification of the third embodiment. FIGS. 11A to 11F are views showing a method for growing a group III nitride semiconductor according to the fourth embodiment. FIG. 12A to FIG. 12F are views showing a method for growing a group III nitride semiconductor according to the fifth embodiment. FIGS. 13A to 13F are views showing a method for growing a group III nitride semiconductor according to the sixth embodiment.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, embodiments of a method for growing a group III nitride semiconductor and a method for manufacturing a group III nitride semiconductor device of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

(First embodiment)
FIG. 1A to FIG. 1F are drawings showing a method for growing a group III nitride semiconductor according to the present embodiment. FIG. 2 shows a crystal growth apparatus that can be used to grow a group III nitride semiconductor according to the present embodiment. The crystal growth apparatus 11 can be a metal organic vapor phase growth furnace. The crystal growth apparatus 11 includes a reaction tube 15 provided in the chamber 13. A susceptor 17 is located in the opening 15 a of the reaction tube 15. A substrate W can be disposed on the susceptor 17. One end 15b of the reaction tube 15 is connected to the pipes 19a to 19g and receives the raw material gas from the pipes 19a to 19g. A mass flow controller is provided in each of the pipes 19a to 19g. The other end 15 c of the reaction tube 15 is connected to the exhaust pump 23 via the gate valve 21. Each mass flow controller can be used to control the gas flow rate. Further, the pressure of the reaction tube 15 can be controlled by adjusting the gate valve 21. Each mass flow controller and gate valve 21 is connected to a controller so that they can be controlled individually or in concert.

  As shown in FIG. 1F, this method includes a step S1 for growing a group III nitride semiconductor, a step S2 for stopping the supply of the group III organometallic material, an afterflow step S3, and a purge step. S4. In the growth step S1, a group III nitride semiconductor is grown on the substrate W. The group III nitride semiconductor is, for example, a gallium nitride-based material or aluminum nitride. The gallium nitride based material is, for example, GaN, AlGaN or the like, and can further include InGaN and InAlGaN. The substrate W can include a group III nitride semiconductor such as a gallium nitride based semiconductor as a base. This base is provided on a group III nitride support such as GaN or AlN.

  In the growth step S1, a gas G1 containing ammonia and a group III organometallic substance is supplied to the growth furnace 15 of the vapor phase growth apparatus 11 to grow a group III nitride semiconductor. As the group III organometallic substance, for example, trimethyl gallium (TMG), trimethyl aluminum (TMAl), or the like can be used. For example, when growing GaN, an ammonia source is supplied from the nitrogen compound source 23a and TMG is supplied from the gallium source 23b. As a bubbling gas for the organic metal raw material, hydrogen gas, nitrogen gas, inert gas, or the like can be used. Separately from these pipes, pipes 19d and 19e for supplying hydrogen gas and nitrogen gas to the reaction furnace 15 are provided. For example, when growing AlGaN, an ammonia source is supplied from the nitrogen compound source 23a, TMG is supplied from the gallium source 23b, and TMAl is supplied from the aluminum source 23c. Further, an n-type dopant source 23f is connected to the reaction furnace 15 via a pipe 19f in order to impart n conductivity to the group III nitride semiconductor, and p in order to impart p conductivity to the group III nitride semiconductor. A type dopant source 23g is connected to the reactor 15 through a pipe 19g.

An example of film formation conditions in the process of growing gallium nitride:
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: 1050 degrees Celsius. In the growth period Ta of the group III nitride semiconductor, the ammonia flow rate is kept constant as shown in FIG. 1A, and the hydrogen flow rate is kept constant as shown in FIG. As shown in FIG. 1D, the TMG supply amount is also kept constant, and the pressure is kept constant as shown in FIG.

  In step S2, as shown in FIG. 1D, the supply of the group III organometallic material to the vapor phase growth apparatus 11 is stopped at time t1. Thereby, the growth of the group III nitride semiconductor is completed.

  In step S3, during the period after time t1, the gas containing ammonia is supplied so that the temperature of the reaction furnace 15 of the vapor phase growth apparatus 11 becomes a temperature Temp2 lower than the temperature Temp1 at time t1 at time t2. The temperature of the phase growth apparatus 11 is changed. During the temperature change period Tb, the supply amount of ammonia is increased.

  Since the supply of the group III organometallic raw material to the vapor phase growth apparatus 11 is stopped and the supply amount of ammonia is increased, the temperature of the vapor phase growth apparatus 11 is set to the temperature after the growth of the group III nitride semiconductor is completed. During the period of changing to Temp2, the number of defective donors generated in the group III nitride semiconductor is reduced.

  In this embodiment, as shown in FIG. 1 (F), the change of the temperature of the reaction furnace 15 is started at time t1. As an example of the temperature change, the growth is performed so that the temperature for growth is 1050 degrees Celsius to a time t2 (for example, 480 seconds after the time t1) and 450 degrees Celsius. Further, the supply amount of ammonia is increased at time t1.

An example of conditions in the afterflow process:
TMG supply amount: 0 μmol / sec
NH ₃ flow rate: 11 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: Decrease from 1050 degrees Celsius to 450 degrees Celsius. In this embodiment, although the supply amount of ammonia is increased in the temperature change period Tb, the supply amount of ammonia is increased during at least one of the growth period Ta and the temperature change period Tb. Also good.

  If the increase in the supply amount of ammonia is started during the growth period Ta, the supply amount of ammonia at the end of the growth of the group III nitride semiconductor is larger than the supply amount of ammonia at the start of the growth of the group III nitride semiconductor. In addition, the supply amount of ammonia during the period of changing the temperature of the vapor phase growth apparatus 11 is greater than or equal to the supply amount of ammonia at the end t1 of the growth of the group III nitride semiconductor. Since the process proceeds to the process of the change period Tb while supplying more ammonia than the initial supply amount of ammonia in the growth period Ta during the growth of the group III nitride semiconductor, generation of defective donors in the group III nitride semiconductor can be reduced.

  If the increase in the supply amount of ammonia is started during the temperature change period Tb, the supply amount of ammonia during the period of changing the temperature of the vapor phase growth apparatus 11 is the supply of ammonia at the end of the growth of the group III nitride semiconductor. More than the amount. Since more ammonia than the final supply amount of ammonia during the growth period Ta is supplied during the change period Tb, the number of defective donors generated in the group III nitride semiconductor is reduced.

  In step S4, as shown in FIGS. 1A and 1B, the supply amounts of ammonia and hydrogen are reduced. Further, as shown in FIG. 1C, nitrogen gas is supplied to the reaction furnace 15. As shown in FIG. 1 (F), the temperature of the reaction furnace 15 is further lowered. Thereby, the temperature of the reaction furnace 15 is about 450 degrees Celsius at the time t2, but the reaction furnace 15 is cooled to a temperature close to room temperature. Further, the pressure in the reactor 15 is also adjusted to normal pressure. Thereafter, the epitaxial substrate on which the group III nitride semiconductor is epitaxially grown is taken out of the reaction furnace 15.

  Such a film forming method is used for manufacturing a group III nitride semiconductor device. As shown in FIG. 3A, this manufacturing method includes a step S111 of preparing a group III nitride wafer, a step S112 of growing a group III nitride semiconductor layer according to the above method, and a group III nitride semiconductor layer. And a step S113 of forming a Schottky electrode thereon. If necessary, one or more group III nitride semiconductor layers can be grown prior to the group III nitride semiconductor layer growth. According to this method, the leakage current of the Schottky junction due to the defective donor on the surface of the group III nitride semiconductor can be reduced. Further, the reduction in the barrier height of the Schottky junction can be reduced. In the Schottky barrier diode, the leakage current of the Schottky electrode is reduced. For example, in a Schottky gate of a high electron mobility transistor, the gate leakage current is reduced.

  Alternatively, as shown in FIG. 3B, this manufacturing method includes a step S121 of preparing a group III nitride wafer, a step S122 of growing a p-type group III nitride semiconductor layer according to the above method, Forming an ohmic electrode on the group nitride semiconductor layer. If necessary, one or more group III nitride semiconductor layers can be grown prior to the growth of the p-type group III nitride semiconductor layer. According to this method, the resistance of the ohmic junction due to the defective donor on the surface of the group III nitride semiconductor can be reduced. It is possible to reduce the contact resistance of an electrode that is in ohmic contact with a p-type group III nitride semiconductor such as a pn junction diode, a pin junction diode, a light emitting diode, or a semiconductor laser. Further, an n-type group III nitride semiconductor layer can be grown instead of the p-type group III nitride semiconductor layer.

(Second Embodiment)
4A to 4F are views showing a method for growing a group III nitride semiconductor according to the present embodiment. The process flow shown in FIGS. 4A to 4F is also performed using the crystal growth apparatus shown in FIG. As shown in FIG. 4F, this method includes a step S11 for growing a group III nitride semiconductor, a step S12 for stopping the supply of the group III organometallic material, an afterflow step S13, and a purge step S14. Including. In the growth step S11, a group III nitride semiconductor is grown on the substrate W.

  In the growth step S11, a gas G1 containing ammonia and a group III organometallic substance is supplied to the growth furnace 15 of the vapor phase growth apparatus 11 to grow a group III nitride semiconductor. For example, when growing GaN, an ammonia source is supplied from the nitrogen compound source 23a and TMG is supplied from the gallium source 23b.

An example of film formation conditions in the process of growing gallium nitride:
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: 1050 degrees Celsius. In the growth period Ta of the group III nitride semiconductor, the ammonia flow rate is kept constant as shown in FIG. 4A, and the hydrogen flow rate is kept constant as shown in FIG. As shown in FIG. 4D, the TMG supply amount is also kept constant, and the pressure is kept constant as shown in FIG.

  In step S12, as shown in FIG. 4D, the supply of the group III organometallic material to the vapor phase growth apparatus 11 is stopped at time t3. Thereby, the growth of the group III nitride semiconductor is completed.

  In step S13, during the period after time t3, the gas containing ammonia is supplied so that the temperature of the reaction furnace 15 of the vapor phase growth apparatus 11 reaches the temperature Temp2 lower than the temperature Temp1 at time t3 at time t4. The temperature of the phase growth apparatus 11 is changed.

  According to this method, since the supply of the group III organometallic material to the vapor phase growth apparatus 11 is stopped and the supply amount of hydrogen is reduced, the vapor phase growth is completed after the growth of the group III nitride semiconductor is completed. It is possible to reduce the occurrence of defective donors in the group III nitride semiconductor during the period of changing the temperature of the device 11 to the temperature Temp2.

  In the present embodiment, as shown in FIG. 4 (F), the temperature change of the reaction furnace 15 is started at time t3. The temperature change in one embodiment is performed so that the temperature for growth is 1050 degrees Celsius to 450 degrees Celsius at time t4 (for example, 480 seconds after time t3). Further, the supply amount of hydrogen is decreased at time t3.

An example of conditions in the afterflow process:
TMG supply amount: 0 μmol / sec
NH ₃ flow rate: 11 slm
H ₂ flow rate: ₂ slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: Decrease from 1050 degrees Celsius to 450 degrees Celsius. In the present embodiment, the hydrogen supply amount is decreased during the temperature change period Tb. However, the hydrogen supply amount is decreased during at least one of the growth period Ta and the temperature change period Tb. Also good.

  If the reduction of the hydrogen supply amount is started during the growth period Ta, the hydrogen supply amount at the end of the growth of the group III nitride semiconductor is smaller than the hydrogen supply amount at the start of the growth of the group III nitride semiconductor. In addition, the supply amount of hydrogen during the period of changing the temperature of the vapor phase growth apparatus 11 is substantially equal to or less than the supply amount of hydrogen at the end of the growth of the group III nitride semiconductor. Since the process proceeds to the process of the change period while supplying less hydrogen than the initial supply of hydrogen during the growth period Ta, it is possible to reduce the occurrence of defective donors in the group III nitride semiconductor.

  If the decrease in the hydrogen supply amount is started during the temperature change period Tb, the hydrogen supply amount during the temperature change period Tb is less than the hydrogen supply amount at the end of the group III nitride semiconductor growth t3. During the change period Tb, an amount of hydrogen smaller than the final amount of hydrogen supplied in the growth period Ta is supplied, so that generation of defective donors in the group III nitride semiconductor can be reduced.

  In step S14, the same process as in step S4 is performed. After step S14, the epitaxial substrate on which the group III nitride semiconductor is epitaxially grown is taken out from the reaction furnace 15. Such a film forming method is used to manufacture the group III nitride semiconductor device described in the first embodiment.

  FIG. 5A to FIG. 5F are drawings showing a method for growing a group III nitride semiconductor according to a modification of the second embodiment. The process flow shown in FIGS. 5A to 5F is also performed using the crystal growth apparatus shown in FIG. As shown in FIG. 5F, this method includes a step S21 for growing a group III nitride semiconductor, a step S22 for stopping the supply of the group III organometallic material, an afterflow step S23, and a purge step S24. Including. In the growth step S21, a group III nitride semiconductor is deposited on the substrate W.

In the growth step S21, a gas G1 containing ammonia and a group III organometallic substance is supplied to the growth furnace 15 of the vapor phase growth apparatus 11 to grow a group III nitride semiconductor.
An example of film formation conditions in the process of growing gallium nitride:
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: 1050 degrees Celsius. In the growth period Ta of the group III nitride semiconductor, the ammonia flow rate is kept constant as shown in FIG. 5A, and the hydrogen flow rate is kept constant as shown in FIG. As shown in FIG. 5D, the TMG supply amount is also kept constant, and the pressure is kept constant as shown in FIG.

  In step S22, as shown in FIG. 4D, the supply of the group III organometallic material to the vapor phase growth apparatus 11 is stopped at time t5. Thereby, the growth of the group III nitride semiconductor is completed.

  In step S23, the temperature of the vapor phase growth apparatus 11 is changed during the period after time t5 as in the second embodiment. In the temperature change period Tb, the supply amount of hydrogen is decreased and the supply amount of ammonia is increased. This method can also reduce the occurrence of defective donors in the group III nitride semiconductor during the period in which the temperature of the vapor phase growth apparatus 11 is changed to the temperature Temp2 after the group III nitride semiconductor has been grown.

  In the present embodiment, as shown in FIG. 5 (F), the temperature change of the reaction furnace 15 is started at time t5. In one embodiment, at time t5, the ammonia flow rate is increased and the hydrogen flow rate is decreased.

An example of film formation conditions in the afterflow process:
TMG supply amount: 0 μmol / sec
NH ₃ flow rate: 16.5 slm
H ₂ flow rate: 3 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: Decrease from 1050 degrees Celsius to 450 degrees Celsius. Step S24 is performed in the same manner as step S4.

  6 (A) to 6 (F) are drawings showing a method for growing a group III nitride semiconductor according to another modification of the second embodiment. The process flow shown in FIGS. 6A to 6F is also performed using the crystal growth apparatus shown in FIG. As shown in FIG. 6F, this method includes a step S31 for growing a group III nitride semiconductor, a step S32 for stopping the supply of the group III organometallic material, an afterflow step S33, and a purge step S34. Including.

  In the growth step S31, a group III nitride semiconductor is deposited on the substrate W. In the growth step S31, a gas G1 containing ammonia and a group III organometallic substance is supplied to the growth furnace 15 of the vapor phase growth apparatus 11 to grow a group III nitride semiconductor. During the growth step S31, the flow rate of ammonia is increased and the flow rate of hydrogen is decreased. At a time prior to time t9, for example, at time t91 (210 seconds before completion of film formation), an increase in the flow rate of ammonia is started. In addition, at a time prior to time t9, for example, at time t91 (210 seconds before completion of film formation), reduction of the hydrogen flow rate is started. At a time prior to time t9, for example, at time t92 (50 seconds before completion of film formation), the increase in the flow rate of ammonia is completed. Further, at the time prior to time t9, for example, at time t92 (50 seconds before film formation is completed), the reduction of the hydrogen flow rate is completed.

Example of film formation conditions in the step of growing gallium nitride (time t91):
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: 1050 degrees Celsius.

An example of film formation conditions in the step of growing gallium nitride (time t92):
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 16.5 slm
H ₂ flow rate: 3.5 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: 1050 degrees Celsius. For example, in the group III nitride semiconductor growth period Ta, the TMG supply amount is kept constant as shown in FIG. 6D, and the pressure is kept constant as shown in FIG. 6E.

  In step S32, as shown in FIG. 6D, the supply of the group III organometallic material to the vapor phase growth apparatus 11 is stopped at time t9. Thereby, the growth of the group III nitride semiconductor is completed.

  In step S33, as shown in FIG. 6F, the change of the temperature of the reaction furnace 15 is started at time t9. This method can also reduce the occurrence of defective donors in the group III nitride semiconductor during the period in which the temperature of the vapor phase growth apparatus 11 is changed to the temperature Temp2 after the group III nitride semiconductor has been grown. The temperature change in one example can be performed in the same manner as in the second embodiment, for example.

An example of conditions in the afterflow process:
TMG supply amount: 0 μmol / sec
NH ₃ flow rate: 16.5 slm
H ₂ flow rate: 3 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: Decrease from 1050 degrees Celsius to 450 degrees Celsius. In step S34, the same process as in step S4 is performed.

  In the above modification, the gas supply amount is changed in either the growth period Ta or the temperature change period Tb, but the supply amount is changed during at least one of the growth period Ta and the temperature change period Tb. You may make it change.

Example 1
A free-standing GaN substrate and a sapphire template are prepared. The dislocation density of the low dislocation free-standing GaN substrate is, for example, 1 × 10 ⁶ cm ⁻² . A free-standing GaN substrate and a sapphire template are placed in a metal organic vapor phase epitaxy (OMVPE) furnace. Perform thermal heat cleaning on the substrate surface. The conditions are a temperature of 990 degrees Celsius, an NH ₃ flow rate of 16.5 slm, an H ₂ flow rate of 3.5 slm, a pressure of 200 torr, and a processing time of 600 seconds. When growing gallium nitride, growth conditions, a temperature of 1050 degrees Celsius, NH ₃ flow rate of 9 slm, _{H 2} flow rate of 11slm, 320μmol / TMG supply amount of sec, the pressure of the flow 200torr of 5 sccm SiH ₄ of diluted 10ppm It is. By this film formation, a 2 μm n ⁺ GaN film is obtained. The carrier concentration is about 1 × 10 ¹⁸ cm ⁻³ .

According to the process shown in FIG. 7, gallium nitride is grown. The growth conditions in step S41 are a temperature of 1050 degrees Celsius, a NH ₃ flow rate of 9 slm, a H ₂ flow rate of 11 slm, a TMG of 320 μmol / sec, a flow rate of 0.2 sccm SiH ₄ diluted to 10 ppm, and a pressure of 200 torr. In step S42, the supply of TMG is terminated at time t7, and the film formation is completed. By this film formation, a 10 μm n ^- GaN film is obtained, and the carrier concentration is about 4 × 10 ¹⁶ cm ⁻³ . After the growth is complete, the temperature starts to drop. In step S43, the temperature is lowered at a constant rate from 1050 degrees Celsius to 450 degrees Celsius with a fall time of 480 seconds. The conditions are 9 slm NH ₃ , 11 slm H ₂ flow rate, and 200 torr pressure. At time t8 (after 480 seconds have elapsed), the temperature of the growth furnace is lowered to 450 degrees Celsius. In step S44, the flow is gradually switched to N ₂ with a flow rate of 8 slm, and the temperature is further lowered to complete the growth flow. Samples manufactured by using these steps and using a GaN substrate and a template are referred to as epitaxial substrates G _A and S _A , respectively.

The manufacturing flow is performed according to the exemplary conditions of the manufacturing flow shown in FIGS. 5 (A) to 5 (F). That is, 16.5 slm is used as the ammonia flow rate and 3.5 slm is used as the hydrogen flow rate in the afterflow process after the growth is completed. Samples similarly produced using the GaN substrate and the template by applying these steps are referred to as epitaxial substrates G _B and S _B , respectively.

Moreover, a manufacturing flow is performed according to the exemplary conditions shown in FIGS. 6 (A) to 6 (F). That is, the increase in the ammonia supply amount (9 slm) is started 210 seconds prior to the end of the growth, and the increase in the ammonia supply amount (16.5 slm) is stopped 30 seconds prior to the end of the growth. Thereafter, the supply amount of ammonia is kept constant (16.5 slm). In addition, a decrease in the hydrogen ammonia supply amount (9 slm) is started 210 seconds prior to the end of the growth, and a decrease in the ammonia supply amount (3.5 slm) is stopped 30 seconds prior to the end of the growth. Thereafter, the supply amount of hydrogen is kept constant (3.5 slm). Samples similarly produced using the GaN substrate and template by applying these steps are referred to as epitaxial substrates G _C and S _C , respectively.

These epitaxial substrate _{G A, S A, G B} , S B, G C, to form a double Schottky electrode on _{S C,} the Schottky barrier diode _{DG A, DS A, DG B} , DS B, DG C, to produce a DS _C. An electrode was produced by vacuum deposition using resistance heating using Au (gold) as a Schottky metal. These devices were evaluated using double Schottky electrodes. The electrical characteristics of the Schottky barrier diodes DG _A , DG _B , DG _C and the Schottky barrier diodes DS _A , DS _B , DS _C are shown.
Element name Withstand voltage (V) Characteristic on-resistance diode DG _A : 181 1.6 mΩcm ²
Diode DG _B : 205 1.6 mΩcm ²
Diode DG _C : 220 1.6 mΩcm ²
Diode DS _A : 112 11 mΩcm ²
Diode DS _B : 118 11 mΩcm ²
Diode DS _C : 132 11 mΩcm ²
The withstand voltage indicates a reverse voltage at 1 mA / cm ² . The characteristic on-resistance indicates resistance at a current density of 200 mA / cm ² .

(Third embodiment)
FIG. 8A to FIG. 8F are diagrams showing a method for growing a group III nitride semiconductor according to the present embodiment. The process flow shown in FIGS. 8A to 8F is also performed using the crystal growth apparatus shown in FIG. As shown in FIG. 8F, this method includes a step S51 for growing a group III nitride semiconductor, a step S52 for stopping the supply of the group III organometallic material, an afterflow step S53, and a purge step S54. Including. In the growth step S51, a group III nitride semiconductor is deposited on the substrate W.

  The growth step S51 can be performed in the same manner as the step S31, for example. In step S52, as shown in FIG. 8D, the supply of the group III organometallic material to the vapor phase growth apparatus 11 is stopped at time t11. Thereby, the growth of the group III nitride semiconductor is completed. Next, an afterflow step S53 is performed. In this embodiment, the supply of nitrogen is increased at times after time t11. In this embodiment, the supply of nitrogen is changed from 0 slm to 11 slm.

  According to this method, since the supply amount of nitrogen is increased simultaneously with or after the supply of the group III organometallic substance to the vapor phase growth apparatus 11, the growth of the group III nitride semiconductor is completed. It is possible to reduce the occurrence of defective donors in the group III nitride semiconductor during the period Tb during which the temperature of the vapor phase growth apparatus 11 is changed to the temperature Temp2.

  In this embodiment, at time after time t11, the supply of nitrogen is increased and the supply of hydrogen is decreased. The reduction of hydrogen reduces the generation of defective donors. It is preferable to stop the supply of hydrogen after the decrease in the supply amount of hydrogen. Moreover, it is preferable to start the decrease in the hydrogen supply at an early time in the afterflow step S53, for example, in response to the stop of the supply of TMG. In particular, the reduction of the hydrogen supply amount is preferably performed at time t11 when the supply of TMG is stopped.

Example of film formation conditions in the step of growing gallium nitride (until time t11):
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: 1050 degrees Celsius.

Example of conditions in the afterflow process (time t11 to t12):
TMG supply amount: 0 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 0 slm
N ₂ flow rate: 11 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: Decrease from 1050 degrees Celsius to 450 degrees Celsius. In step S54, the same process as in step S4 is performed.

  FIG. 9A to FIG. 9F are drawings showing a method for growing a group III nitride semiconductor according to a modification of the third embodiment. The process flow shown in FIGS. 9A to 9F is also performed using the crystal growth apparatus shown in FIG. As shown in FIG. 9F, this method includes a step S61 for growing a group III nitride semiconductor, a step S62 for stopping the supply of the group III organometallic material, an afterflow step S63, and a purge step S64. Including. In the growth step S61, a group III nitride semiconductor is grown on the substrate W. At time t13, supply of TMG is stopped and film formation is completed.

  In the growth step S61, the supply amount of nitrogen is increased at time t131 prior to time t13. In this embodiment, the supply of nitrogen is changed from 0 slm to 11 slm. After the change of the nitrogen supply amount, the afterflow process S63 is started. According to this method, since the process proceeds to the process of the change period Tb while supplying a larger amount of nitrogen than the initial supply of nitrogen during the growth period Ta, the generation of defective donors in the group III nitride semiconductor is reduced. it can. The increase in nitrogen supply is performed, for example, 30 seconds before time t13.

  In this embodiment, for example, at time t131 prior to time t13, the supply of nitrogen is increased and the supply of hydrogen is decreased. The reduction of hydrogen reduces the generation of defective donors. It is preferable to stop the supply of hydrogen after the decrease in supply of hydrogen. Moreover, it is preferable to start the decrease in the hydrogen supply in the latter half of the growth step S61, for example, in response to an increase in nitrogen.

Example of film formation conditions in the step of growing gallium nitride (until time t131):
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 16.5 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: 1050 degrees Celsius.

An example of film formation conditions in the step of growing gallium nitride (after time t131):
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 16.5 slm
H ₂ flow rate: 0 slm
N ₂ flow rate: 11 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: 1050 degrees Celsius.

Example of conditions in the afterflow process (time t13 to t14):
TMG supply amount: 0 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 0 slm
N ₂ flow rate: 11 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: Decrease from 1050 degrees Celsius to 450 degrees Celsius. Step S64 is performed in the same manner as step S4.

  In the above modification, the gas supply amount is changed in either the growth period Ta or the temperature change period Tb, but the supply amount is changed during at least one of the growth period Ta and the temperature change period Tb. You may make it change.

(Example 2)
Using a gallium nitride substrate and a sapphire template, epitaxial substrates G _D , S _D , G _E and S _E are produced in the same manner as in Example 1. Specifically, the exemplary conditions of the manufacturing flow shown in FIGS. 8A to 8F and FIGS. 9A to 9F are used.

Double Schottky electrodes are formed on these epitaxial substrates G _D , S _D , G _E and S _E to produce Schottky barrier diodes DG _D , DS _D , DG _E and DS _E. These devices were evaluated using double Schottky electrodes. The electrical characteristics of Schottky barrier diodes DG _D , DS _D , DG _E , and DS _E are shown.
Element name Withstand voltage (V) Characteristic on-resistance diode DG _A : 181 1.6 mΩcm ²
Diode DG _D : 196 1.6 mΩcm ²
Diode DG _E : 205 1.6 mΩcm ²
Diode DS _A : 112 11 mΩcm ²
Diode DS _D : 122 11 mΩcm ²
Diode DS _E : 125 11 mΩcm ²

(Fourth embodiment)
FIG. 10A to FIG. 10F are drawings showing a method for growing a group III nitride semiconductor according to the present embodiment. The process flow shown in FIGS. 10A to 10F is also performed using the crystal growth apparatus shown in FIG. As shown in FIG. 10F, this method includes a step S71 for growing a group III nitride semiconductor, a step S72 for stopping the supply of the group III organometallic material, an afterflow step S73, and a purge step S74. Including.

  In the growth step S71, a group III nitride semiconductor is deposited on the substrate W. The growth step S71 can be performed, for example, in the same manner as the growth step S1. In step S72, as shown in FIG. 10D, the supply of the group III organometallic material to the vapor phase growth apparatus 11 is stopped at time t15. Thereby, the growth of the group III nitride semiconductor is completed. Next, the afterflow process S73 is started. In this embodiment, the pressure in the furnace is increased at time after time t15. In this embodiment, the pressure is changed from 200 Torr to 500 Torr.

  According to this method, since the pressure during the change period Tb is larger than the pressure at the end of the growth period Ta, generation of defective donors in the group III nitride semiconductor can be reduced.

An example of film formation conditions in the step of growing gallium nitride (until time t15):
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: 1050 degrees Celsius.

Example of conditions in the afterflow process (time t15 to t16):
TMG supply amount: 0 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 66661 Pascal (500 torr)
Temperature in the reactor: Decrease from 1050 degrees Celsius to 450 degrees Celsius. Step S74 is performed in the same manner as step S4.

  FIGS. 11A to 11F are views showing a method for growing a group III nitride semiconductor according to another modification of the fourth embodiment. The process flow shown in FIGS. 11A to 11F is also performed using the crystal growth apparatus shown in FIG. As shown in FIG. 11F, this method includes a step S81 for growing a group III nitride semiconductor, a step S82 for stopping the supply of the group III organometallic material, an afterflow step S83, and a purge step S84. Including. In the growth step S81, a group III nitride semiconductor is grown on the substrate W.

  During the growth step S81, the pressure is increased. At a time prior to time t17, for example, at time t171 (210 seconds before completion of film formation), the pressure starts to increase. Further, at a time prior to time t17, for example, time t172 (50 seconds before completion of film formation), the pressure increase is finished.

An example of film forming conditions in the step of growing gallium nitride (until time t171):
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: 1050 degrees Celsius.

Example of film formation conditions in the step of growing gallium nitride (time t172 to t17):
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 66661 Pascal (500 torr)
Temperature in the reactor: 1050 degrees Celsius.

Example of conditions in the afterflow process (time t17 to t18):
TMG supply amount: 0 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 66661 Pascal (500 torr)
Temperature in the reactor: Decrease from 1050 degrees Celsius to 450 degrees Celsius. Step S84 is performed similarly to step S4.

  In the above modification, the pressure is changed during either the growth period Ta or the temperature change period Tb, but the pressure is changed during at least one of the growth period Ta and the temperature change period Tb. You may do it.

(Example 3)
Using a gallium nitride substrate and a sapphire template, epitaxial substrates G _F , S _F , G _G and S _G are fabricated in the same manner as in Example 1. Specifically, exemplary conditions of the manufacturing flow shown in FIGS. 10A to 10F and FIGS. 11A to 11F are used.

Double Schottky electrodes are formed on these epitaxial substrates G _F , S _F , G _G and S _G to produce Schottky barrier diodes DG _F , DS _F , DG _G and DS _G. These devices were evaluated using double Schottky electrodes. The electrical characteristics of Schottky barrier diodes DG _F , DS _F , DG _G , and DS _G are shown.
Element name Withstand voltage (V) Characteristic on-resistance diode DG _A : 181 1.6 mΩcm ²
Diode DG _F : 211 1.6 mΩcm ²
Diode DG _G : 236 1.6 mΩcm ²
Diode DS _A : 112 11 mΩcm ²
Diode DS _F : 126 11 mΩcm ²
Diode DS _G : 145 11 mΩcm ²

(Fifth embodiment)
FIG. 12A to FIG. 12F are drawings showing a method for growing a group III nitride semiconductor according to the present embodiment. The process flow shown in FIGS. 12A to 12F is also performed using the crystal growth apparatus shown in FIG. As shown in FIG. 12F, this method includes a step S91 for growing a group III nitride semiconductor, a step S92 for stopping the supply of the group III organometallic material, an afterflow step S93, and a purge step S94. Including. In the growth step S91, a group III nitride semiconductor is grown on the substrate W.

  During the growth step S91, the temperature is lowered. At a time prior to time t19, for example, at time t191 (210 seconds before completion of film formation), the temperature starts to decrease. Further, at a time prior to time t19, for example, time t192 (50 seconds before completion of film formation), the pressure reduction is finished.

An example of film forming conditions in the step of growing gallium nitride (until time t191):
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: 1050 degrees Celsius.

An example of film formation conditions in the step of growing gallium nitride (time t192):
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: 1000 degrees Celsius.

An example of film forming conditions in the afterflow process (time t19 to t20):
TMG supply amount: 0 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: Decrease from 1000 degrees Celsius to 450 degrees Celsius. Step S94 is performed in the same manner as step S4.

Example 4
Using the gallium nitride substrate and the sapphire template, epitaxial substrates _GH and _SH are produced in the same manner as in Example 1. Specifically, exemplary conditions of the manufacturing flow shown in FIGS. 12A to 12F are used.

These epitaxial substrate _G H, to form a double Schottky electrode on _{S H,} Schottky barrier diode _DG H, to produce a DS _H. These devices were evaluated using double Schottky electrodes. The electrical characteristics of Schottky barrier diodes DG _H and DS _H are shown.
Element name Withstand voltage (V) Characteristic on-resistance diode DG _A : 181 1.6 mΩcm ²
Diode DG _H : 216 1.6 mΩcm ²
Diode DS _A : 112 11 mΩcm ²
Diode _DS H: 121 _11mΩcm ²

(Sixth embodiment)
FIGS. 13A to 13F are views showing a method for growing a group III nitride semiconductor according to the present embodiment. The process flow shown in FIGS. 13A to 13F is also performed using the crystal growth apparatus shown in FIG. As shown in FIG. 13F, this method includes a step S101 for growing a group III nitride semiconductor, a step S102 for stopping the supply of the group III organometallic material, an afterflow step S103, and a purge step S104. Including. In the growth step S101, a group III nitride semiconductor is grown on the substrate W.

  During the growth step S101, the pressure is increased. At a time prior to time t21, for example, at time t211 (210 seconds before completion of film formation), the pressure starts to increase. At a time prior to time t21, for example, at time t212 (50 seconds before completion of film formation), the pressure increase is finished.

  Further, the supply amount of ammonia is increased during the growth step S101. At a time prior to time t21, for example, at time t211 (210 seconds before completion of film formation), an increase in the supply amount of ammonia is started. At a time prior to time t21, for example, at time t212 (50 seconds before completion of film formation), the increase in the supply amount of ammonia is completed.

  Furthermore, the amount of hydrogen supply is reduced during the growth step S101. At a time prior to time t21, for example, at time t211 (210 seconds before completion of film formation), the reduction of the hydrogen supply amount is started. At a time prior to time t21, for example, at time t212 (50 seconds before completion of film formation), the reduction of the hydrogen supply amount is completed.

  In this embodiment, changes in pressure, ammonia supply amount and hydrogen supply amount start at time t211 and end at time t211. However, if necessary, these change start and end are changed. You may make it carry out at each start time and end time.

Example of film formation conditions in the step of growing gallium nitride (until time t211):
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 9 slm
H ₂ flow rate: 11 slm
N ₂ flow rate: 0 slm
Reactor pressure: 26664 Pascals (200 torr)
Temperature in the reactor: 1050 degrees Celsius.

Example of film formation conditions in the step of growing gallium nitride (time t212):
TMG supply amount: 320 μmol / sec
NH ₃ flow rate: 16.5 slm
H ₂ flow rate: 3.5 slm
N ₂ flow rate: 0 slm
Reactor pressure: 66661 Pascal (500 torr)
Temperature in the reactor: 1050 degrees Celsius.

Example of conditions in the afterflow process (time t21 to t22):
TMG supply amount: 0 μmol / sec
NH ₃ flow rate: 16.5 slm
H ₂ flow rate: 3.5 slm
N ₂ flow rate: 0 slm
Reactor pressure: 66661 Pascal (500 torr)
Temperature in the reactor: Decrease from 1050 degrees Celsius to 450 degrees Celsius. In step S104, the same process as step S4 is performed.

(Example 5)
Using the gallium nitride substrate and the sapphire template, epitaxial substrates G _I and S _I are produced in the same manner as in Example 1. Specifically, exemplary conditions of the manufacturing flow shown in FIGS. 12A to 12F are used.

These epitaxial substrate _G I, to form a double Schottky electrode on _{S I,} to produce a Schottky barrier diode _{DG I,} DS I. These devices were evaluated using double Schottky electrodes. The electrical characteristics of Schottky barrier diodes DG _I and DS _I are shown.
Element name Withstand voltage (V) Characteristic on-resistance diode DG _A : 181 1.6 mΩcm ²
Diode DG _I : 243 1.6 mΩcm ²
Diode DS _A : 112 11 mΩcm ²
Diode DS _I : 151 11 mΩcm ²

As will be understood from the description of the first to sixth embodiments, at least one of the following changes (1) to (5) is made, so that the defective donor is changed during the change period. It is possible to reduce the occurrence of a group III nitride semiconductor.
(1) The supply amount of ammonia is increased during at least one of the growth period Ta and the temperature change period Tb.
(2) The supply amount of hydrogen is reduced during at least one of the growth period Ta and the temperature change period Tb.
(3) The supply amount of nitrogen is increased during at least one of the growth period Ta and the temperature change period Tb.
(4) The temperature of the vapor phase growth apparatus 11 is lowered during the growth period Ta.
(5) The pressure of the vapor phase growth apparatus is increased during at least one of the growth period Ta and the temperature change period Tb. For example, any two combinations of changes (1) to (5), any three combinations of changes (1) to (5), any four combinations of changes (1) to (5), change (1 ) To (5) are possible.

  A method for growing a group III nitride semiconductor and a method for manufacturing a group III nitride semiconductor device described in the present embodiment will be described. For example, the group III nitride semiconductor is preferably AlGaN or AlN. According to this method, it is possible to suppress the formation of defective donors on the surface of the group III nitride semiconductor containing aluminum. For example, the group III nitride semiconductor is preferably n-type GaN. For example, if a Schottky electrode forming a Schottky junction is formed on n-type GaN, the leakage current of the Schottky electrode is reduced. Further, for example, the group III nitride semiconductor is preferably p-type GaN. Specifically, according to this method, if an electrode that forms an ohmic junction with p-type GaN is formed, the contact resistance of the electrode is reduced.

  In the above method according to the present invention, the group III nitride semiconductor is preferably i-type GaN. According to this method, it is possible to suppress the formation of defective donors on the surface of i-type GaN. Thereby, the surface leakage current resulting from the defective donor is reduced on the surface of the i-type GaN.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

11 ... crystal growth apparatus, 13 ... chamber, 15 ... reactor, 17 ... susceptor, W ... substrate, 19A～19g ... pipe, 21 ... gate _{valves, G A ~G I, S A} ~S I ... epitaxial substrate, DG _{A to} DG _I ... Schottky barrier diode, DS _{A to} DS _I ... Schottky barrier diode, Ta ... growth period, Tb ... temperature change period, S1, S21, S31, S41, S51, S61, S71, S81, S91, S101 ... A step of growing a group III nitride semiconductor, S2, S22, S32, S42, S52, S62, S72, S82, S92, S102, a step of stopping the supply of the group III organometallic material, S3, S23, S33, S43, S53, S63, S73, S83, S93, S103 ... After-flow process

Claims (15)

A method for growing a group III nitride semiconductor comprising:
Supplying a gas containing ammonia and a group III organometallic substance to a vapor phase growth apparatus to grow a group III nitride semiconductor;
Stopping the supply of the group III organometallic material to the vapor phase growth apparatus at a first time to end the growth of the group III nitride semiconductor;
The gas containing ammonia is used so that the temperature of the vapor phase growth apparatus becomes a temperature Temp2 lower than the temperature Temp1 of the vapor phase growth apparatus at the first time at a second time after the first time. Changing the temperature of the vapor phase growth apparatus during a period after the first time while supplying,
The nitrogen is increased from the first supply amount to the second supply amount during at least one of the group III nitride semiconductor growth period and the temperature change period of the vapor phase growth apparatus. And how to.   The method according to claim 1, wherein the increase in the supply amount of nitrogen is started during the growth period of the group III nitride semiconductor.   The method according to claim 1, wherein the increase in the supply amount of nitrogen is started during the change period of the temperature of the vapor phase growth apparatus.   4. A method as claimed in any preceding claim, wherein the first supply of nitrogen is substantially zero. A method for growing a group III nitride semiconductor comprising:
Supplying a gas containing hydrogen, ammonia and a group III organometallic substance to a vapor phase growth apparatus to grow a group III nitride semiconductor;
Stopping the supply of the group III organometallic material to the vapor phase growth apparatus at a first time to end the growth of the group III nitride semiconductor;
The gas containing ammonia is used so that the temperature of the vapor phase growth apparatus becomes a temperature Temp2 lower than the temperature Temp1 of the vapor phase growth apparatus at the first time at a second time after the first time. Changing the temperature of the vapor phase growth apparatus during a period after the first time while supplying,
The hydrogen supply amount is decreased during at least one of a growth period of the group III nitride semiconductor and a temperature change period of the vapor phase growth apparatus.   The method according to claim 5, wherein the reduction of the hydrogen supply amount is started during the growth period of the group III nitride semiconductor.   6. The method of claim 5, wherein the reduction of the hydrogen supply is initiated during the change period of the vapor deposition apparatus temperature.   8. A method as claimed in any one of claims 5 to 7, wherein the reduced hydrogen supply is substantially zero.   The method according to claim 5, wherein the supply amount of hydrogen is reduced and nitrogen is supplied to the vapor phase growth apparatus.   9. The method according to any one of claims 5 to 8, wherein the supply amount of ammonia is increased while the supply amount of hydrogen is decreased. A method for growing a group III nitride semiconductor comprising:
Supplying a gas containing ammonia and a group III organometallic substance to a vapor phase growth apparatus to grow a group III nitride semiconductor;
Stopping the supply of the group III organometallic material to the vapor phase growth apparatus at a first time to end the growth of the group III nitride semiconductor;
The gas containing ammonia is used so that the temperature of the vapor phase growth apparatus becomes a temperature Temp2 lower than the temperature Temp1 of the vapor phase growth apparatus at the first time at a second time after the first time. Changing the temperature of the vapor phase growth apparatus during a period after the first time while supplying,
During at least one of the group III nitride semiconductor growth period and the temperature change period of the vapor phase growth apparatus, the pressure of the vapor phase growth apparatus increases from a first pressure value to a second pressure value. A method characterized by that.   The method of claim 10, wherein the increase in pressure is initiated during the growth period of the group III nitride semiconductor.   11. The method of claim 10, wherein the increase in pressure is initiated during the change period of the vapor deposition apparatus temperature. A method for growing a group III nitride semiconductor comprising:
Supplying a gas containing ammonia and a group III organometallic substance to a vapor phase growth apparatus to grow a group III nitride semiconductor;
Stopping the supply of the group III organometallic material to the vapor phase growth apparatus at a first time to end the growth of the group III nitride semiconductor;
The gas containing ammonia is used so that the temperature of the vapor phase growth apparatus becomes a temperature Temp2 lower than the temperature Temp1 of the vapor phase growth apparatus at the first time at a second time after the first time. Changing the temperature of the vapor phase growth apparatus during a period after the first time while supplying,
In the growth period of the group III nitride semiconductor, the temperature of the vapor phase growth apparatus is changed from the temperature Temp3 higher than the temperature Temp1 to the temperature Temp1. A method for growing a group III nitride semiconductor comprising:
Supplying a gas containing ammonia and a group III organometallic substance to a vapor phase growth apparatus to grow a group III nitride semiconductor;
Stopping the supply of the group III organometallic material to the vapor phase growth apparatus at a first time to end the growth of the group III nitride semiconductor;
The gas containing ammonia is used so that the temperature of the vapor phase growth apparatus becomes a temperature Temp2 lower than the temperature Temp1 of the vapor phase growth apparatus at the first time at a second time after the first time. Changing the temperature of the vapor phase growth apparatus during a period after the first time while supplying,
At least one of the following changes (1) to (5) is made:
(1) The supply amount of the ammonia is increased during at least one of the growth period of the group III nitride semiconductor and the temperature change period of the vapor phase growth apparatus.
(2) The supply amount of hydrogen is reduced during at least one of the growth period and the change period.
(3) Nitrogen is increased from the first supply amount to the second supply amount during at least one of the growth period and the change period;
(4) During the growth period, the temperature of the vapor phase growth apparatus is changed from the temperature Temp3 higher than the temperature Temp1 to the temperature Temp1.
(5) During at least one of the growth period and the change period, the pressure of the vapor phase growth apparatus is increased from a first pressure value to a second pressure value.
A method characterized by that.

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