Comparison of electrical properties and deep traps in p Al_x Ga_1-xN grown by molecular beam epitaxy and metal organic chemical vapor deposition

The electrical properties, admittance spectra, microcathodoluminescence, and deep trap spectra of p -AlGaN films with an Al mole fraction up to 45% grown by both metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) were compared. The ionization energy of Mg increases from 0.15 to 0.17 eV in p -GaN to 0.3 eV in 45% Al p -AlGaN. In p -GaN films grown by MBE and MOCVD and in MOCVD grown p -AlGaN, we observed additional acceptors with a concentration an order lower than that of Mg acceptors, with a higher hole capture cross section and an ionization energy close to that of Mg. For some of the MBE grown p -AlGaN, we also detected the presence of additional acceptor centers, but in that case the centers were located near the p -AlGaN layer interface with the semi-insulating AlGaN buffer and showed activation energies considerably lower than those of Mg.