Normally-off C-H Diamond FETs With Partial Al/C-O Diamond Junction Attaining Low off-State Current

Normally- OFF hydrogen-terminated diamond (C-H diamond) field effect transistor (FET) is desirable for safe and energy-saving power switching applications. Whereas, the OFF-state current driven by the power-supply voltage at zero gate bias is relatively high to date, which would generate large static power consumption. In this work, the partial Al/oxygen-terminated diamond (C-O diamond) Schottky gate was utilized to realize normally- OFF operation with a noise-level OFF-state current density (~
$10^{-{9}}$
mA/mm). The partial oxygen-terminated diamond was realized by ultraviolent ozone process with Al2O3-nanoparticle mask. Compared with Al/C-H diamond, the Al/C-O diamond junction possesses a higher Schottky barrier height (SBH) against hole flow, such that the OFF-state current of diamond FETs can be well-suppressed. Also, the enhanced SBH contributes to the negatively shifted threshold voltage, which may avoid device failure from gate overdrive. Moreover, a competitive current density of −91 mA/mm was achieved. Besides, the threshold voltage, ON/OFF ratio, and subthreshold swing were −1.3 V,
${9} \times {10} ^{{9}}$
, and 110 mV/dec, respectively. This approach will promote the application of diamond FETs in power switching system significantly.