The role of deep acceptors for the compensation of undoped SI GaAs

The equilibrium concentrations of singly ionized AsGa/EL2 have been found to exceed the shallow acceptor (C and Zn) concentrations in two series of LEC pBN-GaAs samples. This finding is attributed to the presence of deep acceptors in the low 10 high 15 cm high -3 range and indicates that, in crystals with low C contents, the simple three-level compensation model should be supplemented by a deep acceptor level. Among the acceptors detectable by electron-spin-resonance, FR3 and GR2 appear to be the dominant ones. Formation of FR3 is favored under GA-rich growth contitions.