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 (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BR</sub>). 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 (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub>). 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 SiO<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> mask. As a result, for the fabricated device with a C–Si–O channel length of 2 μm and a gate-to-drain distance (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GD</sub>) of 11 μm, <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TH</sub> = -8.6 V and OFF-state <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BR</sub> = -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.