Low-noise solar-blind AlxGa1-xN-based metal semiconductor-metal ultraviolet photodetectors

We report the growth, fabrication, and characterization of high performance Schottky metal-semiconductor-metal solar-blind photodetectors fabricated o n epitaxial Al0.4Ga0.6N layers grown by metalorganic chemical vapor deposit ion. The devices exhibited low dark current (<2 pA at 30 V) and a gain-enha nced ultraviolet (UV) photocurrent for bias voltages > 40 V. The gain was c orroborated by external quantum efficiency measurements reflecting a quantu m efficiency as high as 49% (at lambda = 272 nm) at 90 V bias, with a corre sponding responsivity R = 107 mA/W. A visible-to-UV rejection factor of mor e than three orders of magnitude was demonstrated. Time-domain and frequenc y-domain speed measurements show a 3-dB bandwidth of similar to 100 MHz. Lo w-frequency noise measurements have determined a detectivity (D*) as high a s 3.3 x 10(10) cm.Hz(1/2)/W for a 500 Hz bandwidth at 37 V bias.