Properties of amorphous GaNx prepared by ion beam assisted deposition at room temperature

Abstract

A theoretical study [P. Stumm and D. A. Drabold, Phys. Rev. Lett. 79, 677 (1997)] has shown that amorphous GaN is a promising wide band gap semiconductor material for electronic and optoelectronic device applications. In this work, a-GaNx and a-GaNx:Er thin films were prepared by means of ion beam assisted evaporation at room temperature in an ultrahigh vacuum chamber. The properties of as-deposited and thermally annealed films were studied by a variety of characterization methods. X-ray diffraction, electron diffraction, and Raman spectroscopy results confirmed that the films are amorphous. Films with gallium to nitrogen ratios of 1.0:0.5–1.0:1.4 were obtained. Films with more nitrogen than gallium were highly transparent to light with energy less than that of the band gap, whereas films with less nitrogen than gallium showed much higher absorption. This indicates that a clean gap can be obtained for nitrogen rich films. Electron spectroscopy results showed that the binding energies for nitrogen and gallium are consistent with only Ga–N bonding with the highest valence band state about 1.5 eV below the Fermi level. Both as-deposited and annealed a-GaNx:Er film showed IR emissions in the range of 950–1000 nm by photoluminescent measurement. The annealed film also showed visible emissions near 700 nm.