Characterization of GeO2 films formed on Ge substrate using high pressure oxidation

Abstract

We investigate germanium oxidation in the GeO2 film fabricated using high pressure oxidation with the goal of improving the electrical properties of the resulting material by suppressing GeO formation. The pressures used during film fabrication were 1, 10, 30, and 50 atm, while the temperatures used were 450, 500, and 550 °C. Au/GeO2/p-Ge and Au/GeO2/n-Ge capacitors were then fabricated using the oxidized GeO2 films. The capacitors were characterized by measuring their capacitance-voltage (C–V). We found that the capacitors are more sensitive to temperature than to pressure in terms of how these process parameters affect the C–V curves of the resulting devices. At constant pressure, the fixed charge (QF) decreases as the temperature increases. The interface trapped charge (QIT) is at its minimum when the film is formed at 500 °C, indicating that higher temperatures cause GeO volatilization. It was also found that using pressure during fabrication is an effective way to suppress GeO formation. The thicknesses of the oxidized GeO2 films were obtained from cross-sectional transmission electron microscopy. X-ray photoelectron spectroscopy depth profiles were quantitatively analyzed to determine the amount of oxygen in the GeO2 films.