A thin-film diamond phototransistor

A phototransistor fabricated from thin-film diamond is reported. Polycrystalline diamond grown by chemical vapor deposition, which is p-type by virtue of near-surface hydrogen, has been used to realize optically activated metal–semiconductor field-effect transistors (FETs). Devices with thin (30 nm) Al Schottky gates and Au source and drain contacts operate as effective enhancement-mode metal–semiconductor field-effect transistors at room temperature; illumination of an electrically isolated gate leads to increased channel current, although saturation is still evident. At deep UV wavelengths (≪220 nm), a photodetector gain of around 4 has been measured; the mechanism of operation has been identified as photodiode-like turn-on followed by FET amplification. © 1999 American Institute of Physics.