Oxidized Si terminated diamond and its MOSFET operation with SiO₂gate insulator

During selective epitaxial growth of diamond through SiO2 masks, silicon terminations were formed on a diamond surface by replacing oxygen terminations under the masks. The high temperature of selective growth and its reductive atmosphere possibly allowed Si atoms in SiO2 to interact with the diamond surface, resulting in silicon terminated diamond (C-Si diamond) composed of a monolayer or thin multi-layers of carbon and silicon bonds on diamond. Diamond metal oxide semiconductor field effect transistors (MOSFETs), with a C-Si diamond channel and selectively grown undoped or heavily boron-doped (p+) source/drain (S/D) layers, have been fabricated. Both the MOSFETs with undoped and p+ S/D exhibited enhancement mode (normally off) FET characteristics. The drain current (IDS) of the undoped device reached -17 mA/mm with threshold voltage (VT) -19 V; the p+ device attained a high IDS -165 mA/mm with a VT of -6 V being one of the best normally off diamond FETs. Transmission electron microscopy and energy dispersive x-ray spectroscopy confirmed the presence of C-Si diamond under the SiO2 masking area. The field effect mobility and interface state density at the C-Si/SiO2 (220 nm)/Al2O3 (100 nm) MOS capacitor are 102 cm2 V-1 s-1 and 4.6 × 1012 cm-2 eV-1, respectively. The MOSFET operation of C-Si diamond provides an alternative approach for diamond.