Integration of Oxidized Silicon- and Hydrogen- Terminated Diamond p-Channels for Normally-Off High-Voltage Diamond Power Devices

With a dense two-dimensional hole gas (2DHG) p-type conductive layer near the surface, hydrogen- terminated (C-H) diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) have shown typical normally-on operations and high breakdown voltages (V-BR). Owing to the high MOS interface quality, the oxidized silicon-terminated (C-Si-O) diamond MOSFETs have featured excellent normally-off characteristics, such as high threshold voltage (V-TH). However, the reported C-Si-O diamond MOSFETs were all exhibited an overlapping-gate structure, and therefore couldn't withstand high voltages. In this work, we demonstrated a novel C-H diamond MOSFET structure with a partial C-Si-O channel to improve the voltage withstand capability of normally-off C-Si-O diamond MOSFETs. The C-H/C-Si-O/C-H channel structure was achieved by forming an entire C-Si-O channel first, and then selectively replacing the C-Si-O channel to the C-H channel by using a SiO2 mask. As a result, for the fabricated device with a C-Si-O channel length of 2 mu m and a gate-to-drain distance (L-GD) of 11 mu m, V-TH = -8.6 V and OFF-state V-BR = -1376 V have been obtained. These competitive results reveal that the proposed device structure is promising in pushing the normally-off C-Si-O diamond MOSFETs into the high voltage applications.