Efficient p-type doping of GaN films by plasma-assisted molecular beam epitaxy

Abstract

In this paper we report on the mechanism of efficient incorporation of Mg in GaN films during growth by plasma-assisted molecular beam epitaxy. It is found that Mg incorporates more efficiently during growth of GaN films at high temperatures (770 °C) under extreme Ga-rich conditions. We propose that this result is due to the dissolution of Mg in the excess Ga on the growth surface and its incorporation into the GaN film via liquid-phase processes. Transport measurements at 300K together with secondary-ion-mass-spectroscopy indicate that the Mg-doping efficiency of GaN under these conditions of growth is 10%. Using this method of doping, p-type GaN films free of Ga droplets, with hole concentrations varying from 2×1017 to 3×1018cm−3 and corresponding mobilities varying from 30 to 2cm2∕Vs, are obtained. The lowest resistivity achieved is 0.3 Ω cm.