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 on epitaxial Al0.4Ga0.6N layers grown by metalorganic chemical vapor deposition. The devices exhibited low dark current (<2 pA at 30 V) and a gain-enhanced ultraviolet (UV) photocurrent for bias voltages >40 V. The gain was corroborated by external quantum efficiency measurements reflecting a quantum efficiency as high as 49% (at=272 nm) at 90 V bias, with a corresponding responsivity R=107 mA/W. A visible-to-UV rejection factor of more than three orders of magnitude was demonstrated. Time-domain and frequency-domain speed measurements show a 3-dB bandwidth of ∼100 MHz. Low-frequency noise measurements have determined a detectivity (D*) as high as 3.3 1010 cm·Hz1/2/W for a 500 Hz bandwidth at 37 V bias.