The effects of post-implantation activation annealing upon deep-level defects in wafers of liquid encapsulated Czochralski semi-insulating material were studied by using the thermally stimulated current technique. Six defect levels (T1 to T6) were detected before the activation anneal. It was found that marked changes in the defect states were caused by activation annealing. One change was a large reduction in the concentrations of T1 (0.21eV), T3 (0.31eV) and T6 (0.58eV), and another change was the generation of a new level, Tx (0.29eV). It was shown that T1, T3 and T6 were generated at temperatures of between 600 and 700C during slow cooling, and that this was related to excess As. The T2 (0.26eV) and T5 (0.38eV) levels existed regardless of annealing temperatures below 950C. The Tx level was generated at temperatures above 700C, and under fast cooling conditions. The cooling rate after annealing was a crucial factor in controlling the levels.

H.Yoshida, M.Kiyama, T.Takebe, M.Yamashita, K.Fujita: Materials Science Forum, 1995, 196-201, 243-8