Deep-Depletion Mode Boron-Doped Monocrystalline Diamond Metal Oxide Semiconductor Field Effect Transistor

Abstract

A p-type deep-depletion mode monocrystalline diamond MOSFET is demonstrated, with a 190-nm-thick controllable channel. Such a device offers new opportunities for a better optimization of the bulk doping versus designed breakdown voltage and the resulting figure of merit. Diamond MOSFETs with Boron doping of ${1.75}\times {10}^{{17}} ~\text {cm}^{-{3}}$ and using 20-nm ALD deposited Al2O3 as the gate oxide show promising IV characteristics, with a clear ON and OFF state operation. The MOSFETs have a normally-ON operation with typical threshold voltages of ${V}_{\text {TH}}=+7$ V and a ON-state drain current of ${I}_{\text {SD}}=1.9~\mu \text{A}$ /mm at ${V}_{\text {SD}}=10$ V and ${V}_{\text {GS}}=-5$ V, at room temperature. A high hole mobility (1000±200 cm2/( $\text {V}\cdot \text {s}$ )) has been evaluated. Just before the experimental voltage breakdown at 200 V, the gate leakage is still below 0.6 nA/mm at room temperature and the peak electric field in diamond at the gate edge is simulated at 4 MV/cm. Beyond this experimental proof of concept, these combined values show the high potential of deep-depletion mode Boron doped diamond MOSFETs.