Electrical characteristics at 4.2 K and high magnetic fields in metal-oxide-semiconductor field-effect transistors utilizing sputter-deposited gate-oxide films

Characteristics of metal-oxide-semiconductor field-effect transistors (MOSFETs) with sputter-deposited gate-oxide films at 4.2 K under high magnetic fields of up to 10 T are presented. The gate-oxide films are deposited by oxygen-argon sputtering of an SiO2 target at 200 °C, much lower than a conventional thermal oxidation temperature of 1000 °C. The MOSFET using a sputter-deposited film has a Hall mobility of 7000 cm2/V s at 4.2 K. The quantum Hall effect and Shubnikov–de Haas oscillations are successfully observed. The magnetic angle dependence of the magnetoresistance and the Shubnikov–de Haas oscillation indicate that this MOSFET has a two-dimensional electron gas. Analysis of the perpendicular magnetoresistance and the quantum Hall effect indicates that this MOSFET has a weakly localized state similar to that of thermal oxide film.