A set of coupled differential equations was formulated which described the charge capture and emission processes of deep levels that exhibited 2 possible charge states. This solution was obtained by considering the steady-state conditions that were imposed by deep-level transient spectroscopic procedures. Three types of defect were distinguished, according to the predominance of one of three different emission processes. By using this model, the deep-level transient spectra of the doubly-charged defects which were observed in semiconductors such as p-type, electron- and proton-irradiated n-type GaAs, and S-doped GaSb could be reproduced. Thermal barriers to carrier capture could be easily introduced into the present equations, and permitted the reproduction of experimental data; even in the case of large lattice relaxation. It was shown that, without further analysis, using the present model, the deep-level transient spectra of defects with 2 states of charge could be misinterpreted; as in the case of the DX center in S-doped GaSb.

E.F.Ferrari, M.Koehler, I.A.Hümmelgen: Physical Review B, 1997, 55[15], 9590-7