Properties of rapid thermal oxidized p-type germanium and its metal-oxide-semiconductor capacitor structure

Abstract

In this study, p-type Ge surface was oxidized using a rapid thermal technique at temperatures of 380°C, 400°C, 450°C and 500°C, and annealing time of 5 min, 10 min and 15 min in oxygen (O2) with fixed flow rate of 1.0 l/min. It was found that the surface roughness of germanium oxide (GeOx) decreases with the increase of oxidation temperature and time due to the uniform desorption of GeOx. The samples oxidized at 450°C and 500°C show low surface roughness. Four different oxidation states, namely, Ge1+, Ge2+, Ge3+, and Ge4+ were confirmed in the thermally oxidized Ge surface. The fractional composition of these oxide species is strongly depended on the oxidation temperature and time. The fabricated MOS (Au/GeOx/Ge) capacitor using the samples oxidized at 450°C and 500°C show low leakage current due to thicker GeOx layer produced by high oxidation rate at such temperatures. A sample oxidized at 450°C was found to show acceptable capacitive behavior up to 500kHz while a sample of 500°C up to 1MHz. The results seem to suggest that an innovative control of Ge oxidation is needed in order to realize a practical Ge MOSFET in near future.