Influence of hydrogen plasma irradiation on defects of ZnO

Abstract

The influence of hydrogen-defect complexes on the properties of n-type ZnO has been studied in terms of annealing and hydrogen plasma irradiation. Both of carrier concentration and Hall mobility increased after the annealing in Ar atmosphere containing Zn (Zn-annealing). The improved electrical properties indicate that the zinc vacancy (VZn) concentration was decreased by the Zn-annealing. While the Zn-annealed sample was not affected by hydrogen plasma irradiation, carrier concentration and Hall mobility of the sample annealed in pure Ar atmosphere were increased by hydrogen plasma irradiation. The simultaneous increases in carrier concentration and Hall mobility indicate that VZn, which acts as a compensation acceptor, is passivated by hydrogen. The carrier concentration and Hall mobility after hydrogen plasma irradiation decreased with increasing post-annealing temperature. It was found that VZn passivated by hydrogen starts to dissociate at temperatures around 400°C. The activation energy for the dissociation of the VZn passivated by hydrogen was estimated to be 2.2 eV.