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 Al2O3 followed by laser separation, were studied by capacitance–voltage and deep level transient spectroscopy (DLTS) measurements. From a 1/C2 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′ with activation energy ET = 0.53 eV was found in the Ga-face sample. Also, trap E1 (ET = 0.18 eV), believed to be related to the N vacancy, was found in the N-face sample, and trap C (ET = 0.35 eV) was in the Ga-face sample. Trap C may have arisen from reactive-ion-etching damage.
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Copyright © 2001, American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters 78.15, and may be found at http://apl.aip.org/resource/1/applab/v78/i15/p2178_s1