Dependence of local electronic structure in p-type GaN on crystal polarity and presence of inversion domain boundaries

Abstract

Scanning probe techniques including scanning capacitance microscopy, scanning capacitance spectroscopy, scanning Kelvin probe force microscopy, and atomic force microscopy have been used to assess structure and local electronic properties of Ga-face and N-face p-type GaN and of inversion domain boundaries in p-type GaN. Epitaxial layers of p-type GaN were grown by molecular-beam epitaxy, and by adjustment of the Ga:N flux ratio samples containing both Ga-face and N-face material were obtained. Under identical growth conditions, net incorporation of electrically active Mg acceptors was found to be more efficient for material with Ga-face polarity. Only a very small dependence of surface potential on polarity was observed, in contrast to results reported for n-type GaN, in which a substantial dependence of Schottky barrier height on polarity has been found. In addition, elevated net concentrations of ionized Mg acceptors were observed in Ga-face regions in the immediate vicinity of some, but not all, inversion domain boundaries, consistent with theoretical suggestions that incorporation of high concentrations of Mg within an inversion domain boundary can lead to increased concentrations of Mg acceptors near the inversion domain boundary.