Comparison of Ge Surface Passivation Between SnGeOx Films Formed by Oxidation of Sn/Ge and SnGex/Ge Structures

SnGeOx films formed by thermal oxidation of Sn/Ge and SnGex/Ge structures were confirmed by X-ray photoelectron spectroscopy and explored to investigate the capability of passivation for GeMOS devices. It is found that Sn incorporation into germanium oxide is effective in suppressing the formation of volatile GeO. For SnGeOx films formed by oxidation of SnGex/Ge structures, due to fewer dislocations between SnGex and Ge, it enjoys an interface trap density of 2.1 x 10(11) cm(-2) . eV(-1), which is lower than those oxidized from Sn/Ge structures. Furthermore, the films also demonstrate desirable electrical characteristics in terms of tiny frequency dispersion and small hysteresis in capacitance measurement, a low leakage current of 9.3 x 10(-10) A/cm(2) at a gate voltage of -1 V with an effective oxide thickness of 3.6 nm, and a good bias temperature instability of 15-mV flatband voltage shift at 85 degrees C after 12.5 MV/cm stress for 1000 s.