Demonstration of solar-blind Al_xGa_(1-x)N-based heterojunction phototransistors

摘要

Al_(0.4)Ga_(0.6)N/Al_(0.65)Ga_(0.35)N heterojunction phototransistors have been fabricated from the epi-structure grown by low-pressure metal organic chemical vapor deposition on c-plane sapphire substrates. P-type conductivity of the AlGaN base layer was realized by using indium surfactant-assisted Mg-delta doping method. Regrowth technique was used to suppress the Mg memory effect on the n-type emitter. The fabricated devices with a 150-μm-diameter active area exhibited a bandpass spectral response between 235 and 285 nm. Dark current was measured to be less than 10 pA for bias voltages below 2.0 V. A high optical gain of 1.9 × 10~3 was obtained at 6 V bias.