Electrical characterization of acceptor levels in Mg-doped GaN

Thermal admittance and current deep-level transient spectroscopy techniques have been applied to Schottky diodes fabricated on Mg-doped GaN grown by metalorganic chemical vapor deposition to investigate the dependence of the Mg acceptor levels on the annealing temperature. Both measurement techniques revealed two deep acceptor levels with activation energies at ?135 and ?160 meV above the valence band. The former level was only seen when the samples were annealed at temperatures between 650 and 700°C, and its presence corresponds with a significant increase in effective acceptor concentration, as confirmed by capacitance-voltage measurements. Therefore, this acceptor level is considered to dominate the electrical activation of Mg in GaN