Low temperature scanning tunneling microscope-induced luminescence of GaN

We report the low temperature scanning tunneling microscope-induced luminescence of molecular beam epitaxy grown alpha-GaN. Semiquantitative spectroscopic analysis suggests near band edge emission, as well as emission covering the rest of the visible range. The relative intensity of band edge emission increases by one order of magnitude under liquid helium cooling. We also report the first photon emission images of GaN obtained with this technique. These images reveal stronger band edge emission at the center of crystallites. This study is complemented with a scanning electron microscope-induced cathodoluminescence analysis. Cathodoluminescence is dominated by the hexagonal (D degrees, X) transition and reveals evidence of small quantities of the cubic phase. (C) 1998 American Vacuum Society.