Solar-blind AlGaN-based Schottky photodiodes grown on 4H-SiC substrate are reported. The fabricated devices demonstrate dark current density as low as 2.2 × 10-10 A/cm2 at a reverse bias of 5 V. A zero-bias peak responsivity of 44 mA/W was achieved at 256 nm, corresponding to an external quantum efficiency of 21%. Under a low illumination power density of 10 nW/cm2, a rejection ratio of more than two orders of magnitude was observed in the wavelength range from 270 to 310 nm. A room-temperature solar-blind detectivity of 7.9 × 1014 cm · Hz1/2W-1 was estimated at 256 nm under zero bias.
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