SiO2-passivated lateral-geometry GaN transparent Schottky-barrier detectors

We report on a transparent Schottky-barrier ultraviolet detector on GaN lay ers over sapphire substrates. Using SiO2 surface passivation, reverse leaka ge currents were reduced to a value as low as 1 pA at 5 V reverse bias for 200 mu m diameter device. The device exhibits a high internal gain, about 5 0, at low forward biases. The response time (about 15 ns) is RC limited, ev en in the internal gain regime. A record low level of the noise spectral de nsity, 5 x 10(-23) A(2)/Hz, was measured at 10 Hz. We attribute this low no ise level to the reduced reverse leakage current. (C) 2000 American Institu te of Physics. [S0003-6951(00)01632-6].