Hydrogen plasma passivation effects on properties of p-GaN

The effects of hydrogen on the electrical and optical properties of p-GaN were investigated. Hydrogen is readily incorporated into the material at temperatures of 250–350 °C, which is consistent with the low activation energy for diffusion reported by Seager et al. [J. Appl. Phys. 92, 7246 (2002)] in GaN p-n junctions. From comparison with the results of earlier experiments, hydrogen diffusivity appears to be a strong function of the hydrogen concentration incorporated into the material during growth. More than an order of magnitude decrease in hole concentration was observed after the hydrogen plasma treatment and from the measurements of the temperature dependence of conductivity. This is the result of hydrogen passivation of acceptors rather than of increased compensation by donor centers. Hydrogen treatment was also shown to lead to a strong suppression of 0.3 eV and 0.6 eV traps and to a strong increase in the magnitude of the photocurrent which are the results of passivation of deep-level defects by hydrogen. At the same time, hydrogen plasma treatment led to a strong increase in the concentration of 0.4 eV hole traps.