High-temperature annealing behavior of p-type doping characteristics in Mg-doped GaN

We report on the high-temperature annealing behavior of p-type doping characteristics in Mg-doped GaN grown by metallorganic chemical-vapor deposition. After activation of Mg dopants by a first 700DGC anneal, the second annealing was sequentially performed with SiO2 encapsulation layers at temperatures between 1000 and 1300DGC. From room-temperature capacitance-voltage measurements, the effective acceptor concentration is seen to increase monotonically with the rise of the annealing temperature up to 1200DGC. In addition, both thermal admittance and current deep-level transient spectroscopic measurements show a gradual decrease in depth of the acceptor levels from 136 to 117 meV with an increase of annealing temperature up to 1200DGC, in which the diffusion of Mg atoms cannot be observed by secondary ion mass spectrometry measurements. Therefore, the enhanced p-type doping characteristics that we observed turn out to be thermally stable even after the high-temperature annealing process.