Demonstration of an AlGaN-based solar-blind high-voltage photoconductive switch

A solar-blind photoconductive semiconductor switch (PCSS) is first fabricated on high-resistivity Al0.4Ga0.6N layer grown on sapphire substrate. The PCSS exhibits a cutoff wavelength of ∼280 nm and a dark resistivity of ∼1012 Ω cm. A maximum blocking voltage of more than 950 V is obtained, corresponding to a breakdown electric-field of >1.35 MV/cm for the active AlGaN layer. When excited by a 266 nm ultraviolet pulsed laser, the PCSS under 500 V bias could produce a peak photocurrent density of 11.5 kA/cm2 within a rise time of ∼15 ns. The fall time of the photocurrent pulse is mainly RC time limited.