III-N semiconductor growth with activated nitrogen: State-specific study of A3Σu+ metastable N2 molecules

High quality epitaxial III-N semiconductor films, ranging in thickness from 300 to 900 Å, have been grown using A3Σu+ metastable nitrogen molecules. The work employed a corona discharge supersonic free-jet to generate a molecular beam containing exclusively the A3Σu+ activation state in an otherwise ground state N2 beam. AlN films were grown on 6H–SiC(0001) and Si(001) substrates. GaN films were grown on the same substrates 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 A3Σu+ molecule) approached 100% and was independent of substrate temperature from 600 to 900 °C, implying direct molecular chemisorption of the A3Σu+. These measurements support theoretical predictions that A3Σu+ is an ideal precursor for III–N growth.