Ultra low dark current solar blind focal plane arrays

The recent developments in high quality GaN/AlGaN material growth technology have led to the realization of high performance solar-blind photodetectors operating in the ultraviolet (UV) spectral region. Diverse applications wherein GaN/AlGaN-based photodetectors are utilized include engine/flame monitoring and detection, plant/vegetation growth monitoring, ozone layer monitoring, UV astronomy, gas detection, water purification, submarine communication, and medical applications. We report on the high performance solar-blind AlGaN-based p-i-n photodetectors that are grown by metal-organic chemical vapor deposition on c-plane sapphire substrates. Back-side illuminated devices show excellent performance under very low reverse biases with very low dark current and high responsivity values. The for bias voltages up to 10 V. The breakdown voltages were higher than 200 V. Focal plane arrays of 320 times 256 with 30 um pitch were realized using p-i-n photodetectors. The responsivities of the back illuminated photodetectors were 0.09 A/W at 270 nm under 2 V reverse biases. We achieved a detectivity of 7.5 times 10¹⁴ cm Hz^1/2 /W for 150 mum diameter back-illuminated AlGaN p-i-n detectors.