Corona discharge supersonic free-jet for III-V nitride growth via A 3Σu+ metastable nitrogen molecules

A corona discharge supersonic free-jet is shown to be a nearly pure source of A (3)Sigma (+)(u) metastable molecular nitrogen, an electronically excited and chemically active form of N-2 that is ideally suited to nitride semiconductor growth. Optical emission spectroscopy at various distances downstream of the supersonic nozzle reveals a cascade through the excited state manifold of N-2 triplet states to populate the A (3)Sigma (+)(u) state. Appearance potential spectroscopy (mass spectrometer electron bombardment ionization yield, measured as a function of electron impact energy) delivers the composition of the terminal molecular beam. A (3)Sigma (+)(u) molecules are the dominant activated species in the beam, which otherwise contains only nonreactive X (1)Sigma (+)(g) ground state nitrogen molecules plus a minor amount of S-4(0) nitrogen atoms. Up to 1.56% number fraction of the beam is A (3)Sigma (+)(u), providing 1.0x10(17) metastables sr(-1) s(-1). (C) 2001 American Institute of Physics.