C–Si bonded two-dimensional hole gas diamond MOSFET with normally-off operation and wide temperature range stability

A C–Si bonded SiO2/diamond interface is formed under a SiO2 mask during the selective diamond growth at a high temperature in a H2 atmosphere including methane (5%). A few monolayers with C–Si bonding at the SiO2/diamond surface are confirmed through X-ray photoelectron spectroscopy at the C1s and Si2p core levels from 290 eV to 271 eV and 107 eV–95 eV, respectively. In addition, secondary ion mass spectroscopy results suggest that the C–Si bonds, and not C–H bonds, are majority at the interface and are mainly responsible for the field effect transistor (FET) operation. Two-dimensional hole gas C–Si diamond metal–oxide–semiconductor FET (MOSFETs) are fabricated using the C–Si diamond sub-surface as a p-channel. The MOSFETs in which the actual length from the source to the drain (LSD) is 12 μm–6 μm show appreciable field-effect mobility (e.g. 140 cm2V−1s−1 at LSD = 12 μm and 300 K) and normally-off operation. The wide temperature characteristics of the C–Si MOSFETs are confirmed and the device shows high stability, and a high on/off ratio of 106 is maintained at 673 K. The C–Si bonding at the SiO2/diamond interface provide a lower interface state density which makes the MOSFET show high drain current density and field-effect mobility with normally-off operation. [Display omitted] •A few monolayers with C–Si bonds are formed on a diamond surface at a high temperature in a reducing gas atmosphere.•The C–Si dipole like C–H dipole is expected to induce the accumulation of a two-dimensional hole gas under an electric field, which can be used as a p-channel to fabricate MOSFETs.•The heavily-boron-doped (p+) selectively grown diamond enhances the performance of the C–Si diamond MOSFET.•The C–Si diamond MOSFET shows excellent field-effect mobility (140 cm2V−1s−1) and normally-off operation.•The C–Si diamond MOSFET with the SiO2 gate insulator shows a high on/off ratio of 106 is maintained at 673 K.