Optimization of Samarium Oxide Deposition on Gallium Arsenide

Samarium oxide (Sm2O3) and samarium gallium oxide (SmxGa1-x)2O3 have been proposed as candidate dielectric materials for the development of gallium arsenide (GaAs) Metal Oxide Semiconductor Field Effect Transistor (MOSFET) technology. Growth of thin (20nm-50nm) Sm2O3 and (SmxGa1-x)2O3 layers on GaAs substrates via plasma-assisted molecular beam epitaxy (MBE) has been performed using a range of growth temperatures and samarium cell temperatures. X-ray photoelectron spectroscopy (XPS) of the deposited films showed evidence of unbonded Sm metal in the films which decreased with decreasing Sm cell temperature, but was relatively independent of substrate temperature. Stoichiometry of the oxide was found to be independent of substrate temperature, but increased in oxygen to metal ratio as the Sm cell temperature was decreased. Decreasing the Sm cell temperature also suppressed the formation of the monoclinic phase and promoted the growth of the cubic phase. Films grown at higher (500şC) temperature showed the presence of a crystalline interface, but relatively high surface roughness and the presence of multiple crystalline phases. Current-voltage analysis of one hundred micron diameter MOS diodes showed breakdown fields at 1 mA/cm2 of up to 4.35 MV/cm. Breakdown field was found to decrease with increasing Sm unbonded metal content in the films. The effect of stoichiometry and phase distribution on the interface state density (Dit) and capacitance-voltage behavior of MOS diodes was also investigated.