Evidence of strong effect from the interface on the electrical characteristics of ZnSe/GaAs heterojunctions

The interface properties of ZnSe/GaAs heterojunctions grown by molecular beam epitaxy have been studied by electrical methods. The current–voltage and capacitance–voltage characteristics show a hysteresis which can be related to unusually slow current and capacitance transients in response to a change in the reverse bias. We performed admittance spectroscopy measurements at various frequencies in order to investigate this phenomenon. A large frequency dispersion of the capacitance and a broad peak in conductance spectra suggest the presence of interface states at the heterojunction between ZnSe and GaAs. We ascribe the long transients to slow changes in the charge on these interface states. We also propose that interface states result in a voltage-induced lowering of the barrier at the heterointerface. The capacitance versus frequency data were analyzed in terms of Lehovec’s model from which the density of interface states of 3–4×1012 cm−2 eV−1 were calculated.