METHOD FOR CONDUCTIVITY CONTROL OF (Al,In,Ga,B)N

Abstract

A method of controlled p-type conductivity in (Al,In,Ga,B)N semiconductor crystals. Examples include {10 1 1} GaN films deposited on {100} MgAl 2 O 4 spinel substrate miscut in the <011> direction. Mg atoms may be intentionally incorporated in the growing semipolar nitride thin film to introduce available electronic states in the band structure of the semiconductor crystal, resulting in p-type conductivity. Other impurity atoms, such as Zn or C, which result in a similar introduction of suitable electronic states, may also be used.

What is claimed is: 
     
         1 . A method of fabricating a semipolar or nonpolar III-nitride semiconductor, comprising:
 controlling a p-type conductivity of the semipolar or nonpolar III-nitride semiconductor, by controlling a hole concentration and a hole mobility in the semipolar or nonpolar III-nitride semiconductor, wherein the hole concentration is approximately at least 10 percent of an acceptor impurity concentration in the semipolar or nonpolar III-nitride semiconductor.   
     
     
         2 . The method of  claim 1 , wherein the III-nitride semiconductor is the semipolar III-nitride semiconductor. 
     
     
         3 . The method of  claim 1 , wherein the III-nitride semiconductor is deposited on a miscut substrate, the method further comprising selecting a miscut angle of a miscut substrate, in order to obtain the desired hole concentration and hole mobility. 
     
     
         4 . The method of  claim 1 , wherein the III-nitride semiconductor is the nonpolar III-nitride semiconductor. 
     
     
         5 . The method of  claim 1 , wherein the fabricating further comprises incorporating dopants either intentionally or unintentionally in the semipolar or nonpolar III-nitride semiconductor. 
     
     
         6 . The method of  claim 5 , wherein the doping comprises varying a flow of Cp 2 Mg during doping and the flow is varied between 0 and 0.3 μmol/minute. 
     
     
         7 . The method of  claim 5 , further comprising performing a subsequent thermal annealing step, after growing and doping the III-nitride semiconductor, that alters a concentration of unintentional impurity atoms within the III-nitride semiconductor, and results in an improvement in conductivity of the III-nitride semiconductor. 
     
     
         8 . The method of  claim 7 , wherein the annealing is to a temperature between 550° C.-850° C. 
     
     
         9 . The method of  claim 7 , wherein the annealing is above 800° C. or at a temperature such that the hole mobility is at least 8 cm 2 /V s. 
     
     
         10 . The method of  claim 1 , wherein the semipolar or nonpolar III-nitride semiconductor is Gallium Nitride and the hole concentration is 10-100% of the acceptor impurity concentration. 
     
     
         11 . The method of  claim 1 , further comprising:
 (a) fabricating the semiconductor III-nitride using an acceptor impurity doped semipolar or nonpolar III-nitride semiconductor; and   (b) controlling the hole concentration and the hole mobility of the acceptor impurity doped semipolar or nonpolar III-nitride semiconductor, thereby controlling the concentration of the acceptor impurity.   
     
     
         12 . A semipolar or nonpolar III-nitride semiconductor, comprising:
 a p-type conductivity based on a controlled hole mobility and a hole concentration in the semipolar or nonpolar III-nitride semiconductor, wherein the hole concentration is approximately at least 10 percent of an acceptor impurity concentration in the semipolar or nonpolar III-nitride semiconductor.   
     
     
         13 . The semiconductor of  claim 12 , wherein the III-nitride semiconductor is the nonpolar III-nitride semiconductor. 
     
     
         14 . The semiconductor of  claim 12 , wherein the III-nitride semiconductor is the semipolar III-nitride semiconductor. 
     
     
         15 . The semiconductor of  claim 14 , wherein the semipolar III-nitride semiconductor comprises Gallium Nitride (GaN). 
     
     
         16 . The semiconductor of  claim 15 , wherein the semipolar GaN comprises {10-1-3}, {10-1-1},{10-12}, {20-21}, {10-14}, or {11-22} GaN. 
     
     
         17 . The semiconductor of  claim 15 , wherein the semipolar GaN comprises {10-1-3} GaN. 
     
     
         18 . The semiconductor of  claim 15 , wherein the semipolar GaN comprises {10-11} GaN. 
     
     
         19 . The semiconductor of  claim 12 , wherein the III-nitride semiconductor comprises has the hole mobility of at least 8 cm 2 /V s. 
     
     
         20 . The semiconductor of  claim 19 , further comprising a hole mobility of 8-14 cm 2 /V s. 
     
     
         21 . The semiconductor of  claim 12 , wherein the III-nitride semiconductor is fabricated using a process comprising:
 growing the semipolar or nonpolar III-nitride semiconductor by Metal Organic Chemical Vapor Deposition on a substrate crystal orientation, comprising:
 selecting and flowing gas flows chosen from a plurality of nitrogen, hydrogen, ammonia, Trimethylgallium (TMGa), and Trimethylaluminum (TMAl), 
 setting a pressure between 10 torr and 1000 torr, and 
 setting a temperature between 400° C. and 1400° C.; 
   controlling a Cp 2 Mg flow during the growing, thereby doping the semipolar or nonpolar III-nitride semiconductor; and   annealing the semipolar or nonpolar III-nitride semiconductor in a hydrogen deficient gas for an anneal time.   
     
     
         22 . The semiconductor of  claim 12 , wherein:
 the semipolar or nonpolar III-nitride semiconductor is Gallium Nitride,   the hole concentration is at least as high as a hole concentration in a semipolar or nonpolar III-nitride semiconductor fabricated using a process comprising:
 growing the semipolar or nonpolar III-nitride semiconductor by Metal Organic Chemical Vapor Deposition on a substrate crystal orientation, comprising:
 selecting and flowing gas flows chosen from a plurality of nitrogen, hydrogen, ammonia, Trimethylgallium (TMGa), and Trimethylaluminum (TMAl), 
 setting a pressure between 10 torr and 1000 torr, and 
 setting a temperature between 400° C. and 1400° C.; 
 
 controlling a Cp 2 Mg flow during the growing, thereby doping the semipolar or nonpolar III-nitride semiconductor; and 
 annealing the semipolar or nonpolar III-nitride semiconductor in a hydrogen deficient gas for an anneal time to a temperature between 550° C.-850° C. 
   
     
     
         23 . The semiconductor of  claim 12 , wherein the semipolar or nonpolar III-nitride semiconductor is Gallium Nitride and the hole concentration is 10-100% of the acceptor impurity concentration. 
     
     
         24 . The semiconductor of  claim 12 , wherein the hole concentration is at least 10 18  cm −3 . 
     
     
         25 . A method of fabricating a III-nitride semiconductor, comprising:
 doping an acceptor impurity into a nonpolar or semipolar III-nitride semiconductor; and   performing a subsequent thermal annealing step, resulting in an improvement in a conductivity of the acceptor impurity doped nonpolar or semipolar III-nitride semiconductor.