Deep centers in a free-standing GaN layer

Schottky barrier diodes, on both Ga and N faces of a similar to 300-mum-thi ck free-standing GaN layer, grown by hydride vapor phase epitaxy (HVPE) on Al2O3 followed by laser separation, were studied by capacitance-voltage and deep level transient spectroscopy (DLTS) measurements. From a 1/C-2 vs V a nalysis, the barrier heights of Ni/Au Schottky contacts were determined to be different for the two polar faces: 1.27 eV for the Ga face, and 0.75 eV for the N face. In addition to the four common DLTS traps observed previous ly in other epitaxial GaN including HVPE-grown GaN a new trap B-' with acti vation energy E-T=0.53 eV was found in the Ga-face sample. Also, trap E-1 ( E-T=0.18 eV), believed to be related to the N vacancy, was found in the N-f ace sample, and trap C (E-T=0.35 eV) was in the Ga-face sample. Trap C may have arisen from reactive-ion-etching damage. (C) 2001 American Institute o f Physics.