Photo-induced current transient spectroscopic measurements were carried out in order to investigate the effects of hydrogenation upon deep levels which existed in undoped p-type material that had been grown, by means of molecular beam epitaxy, onto undoped p-type (111)B-oriented substrates. Four hole traps in the as-grown p-type epilayer were detected, with activation energies of Ev + 0.22 (H1), Ev + 0.38 (H2), Ev + 0.45 (H3) and Ev + 0.63eV (H4). A defect level at Ev + 0.74eV (H5), which originated from Cd vacancies, was not observed. As the growth temperature was increased, the H4 peak which was related to crystal defects disappeared. Also, the H1 peak that was associated with shallow impurities and the H2 peak that was related to Te vacancies, increased. The disappearance of the H4 peak was caused by an increase in Te mobility at high growth temperatures. When the p-type epilayer was hydrogenated, the magnitude of the H1 trap increased slightly, while that of the H2 and H3 traps decreased and the H5 trap disappeared. The decreases in the magnitudes of the H2 and H3 traps after hydrogenation were attributed to acceptors that were related to vacancies which were passivated by H atoms. The results indicated that the H2 and H3 hole traps in undoped p-type material comprised complexes of vacancies and crystal defects.

M.D.Kim, T.W.Kang, T.W.Kim: Solid State Communications, 1996, 99[2], 117-21