Deep levels in annealed low-temperature molecular beam epitaxial layers were characterized by using capacitance deep-level transient spectroscopy. No mid-gap level was detected in samples which had been annealed at 620C, and the highest resistivity of low-temperature layers occurred around this temperature. On the other hand, the EL2 level appeared upon annealing at temperatures above 720C although increasing the annealing temperature decreased the resistivity of low-temperature layers.

T.C.Lin, S.Indou, T.Okumura: Materials Science Forum, 1995, 196-201, 255-60