A thin-film diamond phototransistor

A phototransistor fabricated from thin-film diamond is reported. Polycrystalline diamond grown by chemical vapor deposition, which is a-type by virtue of near-surface hydrogen, has been used to realize optically activated metal-semiconductor held-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. (C) 1999 American Institute of Physics. [S0003-6951(99)02902-2].