Deep centers in a free-standing GaN layer.

Schottky barrier diodes, on both Ga and N faces of a ∼300-μm-thick free-standing GaN layer, grown by hydride vapor phase epitaxy (HVPE) on Al[sub 2]O[sub 3] followed by laser separation, were studied by capacitance-voltage and deep level transient spectroscopy (DLTS) measurements. From a 1/C[sup 2] vs V analysis, 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 previously in other epitaxial GaN including HVPE-grown GaN a new trap B[sup ′] with activation energy E[sub T]=0.53 eV was found in the Ga-face sample. Also, trap E[sub 1] (E[sub T]=0.18 eV), believed to be related to the N vacancy, was found in the N-face sample, and trap C (E[sub T]=0.35 eV) was in the Ga-face sample. Trap C may have arisen from reactive-ion-etching damage. [ABSTRACT FROM AUTHOR]