Low interface state density at an epitaxial ZnSe/epitaxial GaAs interface

The capacitance-voltage (C-V) and the current-voltage characteristics of metal/ZnSe/p-GaAs capacitors have been investigated; both epitaxial layers were grown by molecular beam epitaxy. In the capacitor structures highly resistive, stoichiometric ZnSe functioned as the pseudoinsulator on the doped GaAs layers. The capacitance-voltage measurements demonstrated that the capacitors could be biased from accumulation through depletion, and into deep depletion, with current in the range of 10^-8 A cm^-2. Very little frequency dispersion was observed in the C-V data when measured from 1 kHz to 1 MHz. From the high-frequency C-V curve, the surface state density as a function of position in the GaAs band gap was determined. Surface state densities were comparable to densities reported for (Al,Ga)As/GaAs heterojunctions.