The H passivation of Zn acceptors, and Zn-H dissociation kinetics, were compared for the cases of homo-epitaxial and lattice-mismatched hetero-epitaxial n+p structures. Doping profile measurements revealed a marked increase in the depth and degree of passivation in the p-type region of hetero-epitaxial samples. This indicated an enhanced diffusion of H along dislocations, followed by additional Zn deactivation. Also, the strong affinity between H and extended defects was found to promote the subsequent dissociation of Zn-H complexes. This was revealed by reverse bias annealing studies which showed that the Zn-H dissociation energy decreased, from 1.19eV in homo-epitaxial samples, to 1.12eV in hetero-epitaxial samples. Another indicator was the enhanced passivation of extended defect-related traps by H that was liberated from Zn acceptors during the reverse bias annealing process; as determined by means of deep level transient spectroscopy.

B.Chatterjee, S.A.Ringel: Applied Physics Letters, 1996, 69[6], 839-41