Nitride semiconductor and nitride semiconductor crystal growth method

Abstract

A base at least one principal plane of which is a nitride is prepared for use in epitaxial growth. The base is placed on a susceptor in an epitaxial growth reactor and heated to a predetermined temperature (step A). The heating is started with inactive, nitrogen gas being supplied into the reactor. Then, active, NH 3 gas is supplied. Then, a growth step (step B) of a first nitride semiconductor layer is started without an intervening step of thermally cleaning the principal nitride plane of the base. In step B, the first nitride semiconductor layer is epitaxially grown on a principal nitride plane of a base without supply of an Si source material. Then, a relatively thick, second nitride semiconductor layer is epitaxially grown on the first nitride semiconductor layer by supplying an n-type dopant source material (step C).

1 . (canceled) 
     
     
         2 . A nitride semiconductor crystal growth method for growing a crystal of a nitride semiconductor on a principal nitride plane of a base at least one principal plane of which is a nitride, the nitride semiconductor crystal growth method comprising:
 heating said base for a period including a period t A  during which the base is heated to a predetermined temperature with the principal nitride plane of the base exposed to an atmosphere containing ammonia gas, but not containing hydrogen gas;   a growing step of epitaxially growing a first nitride semiconductor layer on the principal nitride plane of the base with the principal nitride plane of the base exposed to an atmosphere containing ammonia gas,   wherein a flow ratio of an inactive gas component to all constituent gases is between 0.5 and 1.0 both inclusive in the heating step, and   a flow ratio of an active gas component to all constituent gases is between 0.5 and 1.0 both inclusive in the growing step.   
     
     
         3 . A nitride semiconductor crystal growth method for growing a crystal of a nitride semiconductor on a principal nitride plane of a base at least one principal plane of which is a nitride, the nitride semiconductor crystal growth method comprising:
 heating said base for a period including a period t A  during which the base is heated to a predetermined temperature in an atmosphere having a main flow containing ammonia gas, but not containing hydrogen gas;   a growing step of epitaxially growing a first nitride semiconductor layer on the principal nitride plane of the base in an atmosphere having a main flow containing ammonia gas   wherein a flow ratio of an inactive gas component to all constituent gases is between 0.5 and 1.0 both inclusive in the heating step, and   a flow ratio of an active gas component to all constituent gases is between 0.5 and 1.0 both inclusive in the growing step.   
     
     
         4 . The nitride semiconductor crystal growth method according to  claim 3 , wherein before the heating period t A , the heating step has a period t B  during which the base is heated in an atmosphere having a main flow containing a gas composition different from the main flow used during the heating period t A . 
     
     
         5 . The nitride semiconductor crystal growth method according to  claim 3 , wherein the main flow also contains an inactive gas during the heating period t A , wherein
 the inactive gas is at least one gas selected from the group consisting of nitrogen (N 2 ), helium (He), argon (Ar), xenon (Xe), krypton (Kr), a hydrazine compound, an amine compound, and an azide compound.   
     
     
         6 . The nitride semiconductor crystal growth method according to  claim 3 , wherein: the main flow in the growing step include at least a first main flow and a second main flow; the first main flow mainly supplies a nitrogen source material constituting the nitride semiconductor layers; and the second main flow mainly supplies source materials for elements other than nitrogen constituting the nitride semiconductor layers. 
     
     
         7 . The nitride semiconductor crystal growth method according to  claim 2 , wherein the growth step is carried out without thermally cleaning the principal nitride plane of the base after the heating step is finished. 
     
     
         8 . The nitride semiconductor crystal growth method according to  claim 3 , wherein the growth step is carried out without thermally cleaning the principal nitride plane of the base after the heating step is finished. 
     
     
         9 . The nitride semiconductor crystal growth method according to  claim 2 , wherein the epitaxial growth temperature T g1  of the first nitride semiconductor layer in the growing step is between 750° C. and 1,350° C. both inclusive. 
     
     
         10 . The nitride semiconductor crystal growth method according to  claim 9 , wherein the epitaxial growth temperature T g1  of the first nitride semiconductor layer in the growing step is between 900° C. and 1,350° C. both inclusive. 
     
     
         11 . The nitride semiconductor crystal growth method according to  claim 3 , wherein the epitaxial growth temperature T g1  of the first nitride semiconductor layer in the growing step is between 750° C. and 1,350° C. both inclusive. 
     
     
         12 . The nitride semiconductor crystal growth method according to  claim 11 , wherein the epitaxial growth temperature T g1  of the first nitride semiconductor layer in the growing step is between 900° C. and 1,350° C. both inclusive.