Deep level defects in n-type GaN compensated with Mg

Deep level defects in n-type epitaxial GaN compensated with Mg were measured using photocapacitance spectroscopy on Schottky barrier diodes. The doped GaN was prepared by atmospheric pressure metalorganic vapor phase epitaxy using bis(cyclopentadienyl)magnesium as the dopant source. The Mg-doped GaN films were n type as determined by Hall-effect measurements. Addition of magnesium resulted in the formation of a series of deep centers with optical threshold energies of 1.0, 1.2, 1.8, and 3.1 eV. Upon annealing the Mg compensated GaN in nitrogen at 850°C the midgap levels disappeared and only the trapping level at 3.1 eV remained. The midgap levels are ascribed to Mg dopant complexes which may be responsible for low doping efficiency of Mg in the as-grown, doped GaN as well as its semi-insulating behavior.