Comparison of Ge Surface Passivation Between $ \hbox{SnGeO}_{x}$ Films Formed by Oxidation of Sn/Ge and $ \hbox{SnGe}_{x}/\hbox{Ge}$ Structures

SnGeO
x
films formed by thermal oxidation of Sn/Ge and SnGe
x
/Gestructures were confirmed by X-ray photoelectron spectroscopy and explored to investigate the capability of passivation for Ge MOS devices. It is found that Sn incorporation into germanium oxide is effective in suppressing the formation of volatile GeO. For SnGeO
x
films formed by oxidation of SnGe
x
/Ge structures, due to fewer dislocations between SnGe
x
and Ge, it enjoys an interface trap density of 2.1 × 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 × 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°C after 12.5 MV/cm stress for 1000 s.