Electrical properties 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 vapour deposition to investigate the dependence of the Mg acceptor levels on the annealing temperature. Both measurements revealed two deep acceptor levels with activation energies of similar to135 and similar to160 meV above the valence band. The former level is only seen when the samples were annealed at temperatures between 650 degreesC and 700 degreesC, 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.