Novel Methods of p-type Activation in Mg-doped GaN

We have developed two methods for the p-type activation of Mg-doped GaN; a low-temperature long-time annealing method and a RF input activation method. In the low-temperature long-time annealing method, hole concentration increased in proportion to the square root of annealing time. It took ∼ 80 h to obtain hole concentrations of ∼ 1018 cm-3 at 385°C annealed in air. In the RF input activation method, hole concentration increased with the product of RF input time and amplitude of the RF electric field. It took ∼ 70 s to get hole concentrations of ∼ 1018 cm-3 at a RF electric field of ∼ 21 kV/cm. No specific difference was observed for the optical and electrical properties as compared to those of thermally activated samples annealed between 475°C and 800°C in a N2 atmosphere. The photoluminescence (PL) intensity was found to decrease with increasing hole concentration in all activation methods. Nonradiative recombination process is thought to become dominant at hole concentrations over ∼ 2×1016 cm-3 independent of the activation method.