Hydrogen passivation of Ca acceptors in GaN

Exposure to a hydrogen plasma at 250 degrees C of p-type GaN (Ca) prepared by either Ca+ or Ca+ plus P+ co-implantation leads to a reduction in sheet carrier density of approximately an order of magnitude (1.6X10(12) cm(-2) to 1.8X10(11) cm(-2)), and an accompanying increase in hole mobility (6 cm(2)/V s to 18 cm(2)/V s). The passivation process can be reversed by posthydrogenation annealing at 400-500 degrees C under a N-2 ambient. This reactivation of the accepters is characteristic of the formation of neutral (Ca-H) complexes in the GaN. The thermal stability of the passivation is similar to that of Mg-H complexes in material prepared in the same manner (implantation) with similar initial doping levels. Hydrogen passivation of acceptor dopants in GaN appears to be a ubiquitous phenomenon, as it is in other p-type semiconductors. (C) 1996 American Institute of Physics.