Dependence of the Mg-related acceptor ionization energy with the acceptor concentration in p-type GaN layers grown by molecular beam epitaxy

Hall effect and capacitance-voltage C(V) measurements were performed on p-type GaN:Mg layers grown on GaN templates by molecular beam epitaxy with a high range of Mg-doping concentrations. The free hole density and the effective dopant concentration N-A - N-D as a function of magnesium incorporation measured by secondary ion mass spectroscopy clearly reveal both a magnesium doping efficiency up to 90% and a strong dependence of the acceptor ionization energy Ea with the acceptor concentration N-A. These experimental observations highlight an isolated acceptor binding energy of 245 +/- 25 meV compatible, at high acceptor concentration, with the achievement of p-type GaN: Mg layers with a hole concentration at room temperature close to 10(19) cm(-3). (C) 2013 AIP Publishing LLC.