High Quantum Efficiency Back-Illuminated AlGaN-Based Solar-Blind Ultraviolet p–i–n Photodetectors

AlGaN-based back-illuminated solar-blind ultraviolet (UV) p–i–n photodetectors (PDs) with high quantum efficiency are fabricated on sapphire substrates. To improve the overall performance of the PD, a series of structural design considerations and growth procedures are implemented in the epitaxy process. A distinct wavelength-selective photo-response peak of the PD is obtained in the solar-blind region. When operating in photovoltaic mode, the PD exhibits a solar-blind/UV rejection ratio of up to 4 orders of magnitude and a peak responsivity of ～113.5 mA/W at 270 nm, which corresponds to an external quantum efficiency of ～52%. Under a reverse bias of ?5 V, the PD shows a low dark current of ～1.8 pA and an enhanced peak quantum efficiency of ～64%. The thermal noise limited detectivity is estimated to be ～3.3×10¹³ cm?Hz^1/2W^?1.