High-quality germanium dioxide thin films with low interface state density using a direct neutral beam oxidation process

High-quality germanium dioxide (GeO ₂) as a gate oxide is in high demand for use in future high mobility Ge-channel field-effect transistors. GeO ₂ thin films were directly formed by using a damage-free and low-temperature process of neutral beam oxidation (NBO) after treatment with hydrogen (H) radicals. GeO ₂ thin films (equivalent oxide thickness (EOT) 1.7 nm) with a high-quality interface and an extremely low interface state density (<1 × 10 ¹¹cm ^-2eV ^-1) could be formed even at low temperature (300 °C) by combining the H radical treatment, which resulted in the removal of native oxides, with the NBO process we developed.