SI/GE/S MULTILAYER PASSIVATION OF GAAS(100) FOR METAL-INSULATOR-SEMICONDUCTOR CAPACITORS

We describe a new multilayer passivation method on GaAs(100), an ex situ method that doesn't require GaAs epitaxy. Thin 20 angstrom Si films or thin films consisting of 15 angstrom Si and 5 angstrom Ge were grown on (NH4)2S cleaned and S passivated GaAs(100) wafers. High-energy resolution x-ray photoelectron spectroscopy has been used to study the chemical structure of the buried GaAs surfaces. As and Ga 3d core level studies show that the surface is free of gallium and arsenic oxides as well as elementary As. The Ga-S-Ga bridge bond termination is found preserved on the buried GaAs surface. SiN(x)/Si/Ge/S/GaAs and SiN(x)/Si/S/GaAs capacitors have been made and analyzed using quasistatic and high frequency capacitance-voltage measurements. Using the high-low method, an interface state density of about 10(12) cm-2 eV-1 is obtained. The modulation of the surface potential is the highest reported for a method not requiring GaAs epitaxy.