III-N semiconductor growth with activated nitrogen: State-specific study of A(3)Sigma(+)(u) metastable N-2 molecules

High quality epitaxial III-N semiconductor films, ranging in thickness from 300 to 900 Angstrom, have been grown using A(3)Sigma (+)(u) metastable nit rogen molecules. The work employed a corona discharge supersonic free-jet t o generate a molecular beam containing exclusively the A(3)Sigma (+)(u) act ivation state in an otherwise ground state N-2 beam. AlN films were grown o n 6H-SiC(0001) and Si(001) substrates. GaN films were grown on the same sub strates and on buffer layers of AlN deposited in situ on 6H-SiC(0001). The N-atom incorporation efficiency (the number of N atoms attaching to a III-N surface per incident A(3)Sigma (+)(u) molecule) approached 100% and was in dependent of substrate temperature from 600 to 900 degreesC, implying direc t molecular chemisorption of the A(3)Sigma (+)(u). These measurements suppo rt theoretical predictions that A(3)Sigma (+)(u) is an ideal precursor for III-N growth. (C) 2000 American Institute of Physics. [S0003-6951(00)02645- 0].