C-Si interface on SiO2/(111) diamond p-MOSFETs with high mobility and excellent normally-off operation

In this paper, a diamond-silicon (C-Si) interface was constructed on a (1 1 1) diamond substrate by annealing the SiO2 gate insulator in a reductive atmosphere. Corresponding metal-oxide-semiconductor field effect transistors (MOSFETs) with a C-Si conductive channel were fabricated. The MOSFETs demonstrate excellent normally-off operation with a high threshold voltage (Vth) of -16 V and a high current density of -167 mA/mm, with a gate length (LG) of 4 mu m. The channel hole mobility (mu FE) reaches 200 cm2V- 1s- 1 with a LG of 10 mu m, and the interface state density (Dit) is as low as 3.8 x 1011 cm-2 eV-1. The high-resolution transmission electron microscopy (HRTEM) image displays a coherent and strain-free interface between the SiO2 film and (111) diamond, which ensures a high mu FE and low Dit in the MOSFETs. The interface is dominated by C-Si bonds, which are confirmed by atomic-scale electron energy loss (EELS) quantification, spectroscopic characterization, and X-ray photoelectron spectroscopy (XPS). These results demonstrate that diamond, directly combined with SiO2, is ideal for implementation in power devices.