Photo-induced current transient spectroscopic measurements of molecular beam epitaxial strained heterostructures were carried out in order to investigate the hydrogenation and annealing behavior of deep levels which were due to crystal defects. Six hole-traps were detected in as-grown CdTe epilayers. As the growth temperature and the rapid thermal annealing temperature were increased, the intensities of the H5 and H6 peaks, due to crystal defects, decreased while that of a peak which was related to shallow impurities increased. After annealing, the H5 and H6 deep levels did not disappear from the heterostructures. This indicated that the H5 and H6 deep levels were related to crystal defects that arose from lattice mismatch. Whereas the H6 signal was markedly affected by the growth temperature of the epilayer, it was independent of the CdTe layer thickness. The results indicated that the crystallinity of a CdTe epilayer grown on GaAs(100) was improved by rapid thermal annealing, and that improvements in CdTe crystallinity were due to the elimination of defects that formed at the hetero-interface during the growth of CdTe epilayers.

M.D.Kim, T.W.Kang, T.W.Kim: Journal of Applied Physics, 1998, 83[1], 349-52