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 be am 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 chan ge in the reverse bias. We performed admittance spectroscopy measurements a t various frequencies in order to investigate this phenomenon. A large freq uency dispersion of the capacitance and a broad peak in conductance spectra suggest the presence of interface states at the heterojunction between ZnS e 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 capacit ance versus frequency data were analyzed in terms of Lehovec's model from w hich the density of interface states of 3-4x10(12)cm(-2)eV(-1) were calcula ted. (C) 1999 American Institute of Physics. [S0021-8979(99)00207-8].