High-performance solar-blind AlGaN photodetectors

摘要

Design, fabrication, and characterization of high-performance Al_xGa_(1-x)N-based photodetectors i'or solar-blind applications are reported. Al_xGa_(1-x)N heterostructures were designed for Schottky, p-i-n, and metal-semiconductor-metal (MSM) photodiodes. The solar-blind photodiode samples were fabricated using a microwave compatible fabrication process. The resulting devices exhibited extremely low dark currents. Below 3 fA leakage currents at 6 V and 12 V reverse bias were measured on p-i-n and Schottky photodiode samples respectively. The excellent current-voltage (I-V) characteristics led to a detectivity performance of 4.9x10~(14) cmHz~(1/2)W~(-1). The MSM devices exhibited photoconductive gain, while Schottky and p-i-n samples displayed 0.15 AAV and 0.11 AAV peak responsivity values at 267 nm and 261 nm respectively. All samples displayed true solar-blind response with cut-off wavelengths smaller than 280 nm. A visible rejection of 4x10~4 was achieved with Schottky detector samples. High speed measurements at 267 nm resulted in fast pulse responses with >GHz bandwidths. The fastest devices were MSM photodiodes with a maximum 3-dB band width of 5.4 GHz.