All AlGaN epitaxial structure solar-blind avalanche photodiodes with high efficiency and high gain

Solar-blind avalanche photodiodes were fabricated with an all AlGaN-based epitaxial structure on sapphire by metal-organic chemical vapor deposition. The devices demonstrate a maximum responsivity of 114.1 mA/W at 278 nm and zero bias, corresponding to an external quantum efficiency (EQE) of 52.7%. The EQE improves to 64.8% under a bias of -10V. Avalanche gain higher than 2 x 10(4) was obtained at a bias of -140V. The high performance is attributed to the all AlGaN-based p-i-n structure comprised of undoped and Si-doped n-type Al0.4Ga0.6N on a high quality AlN layer and highly conductive p-type AlGaN grown with In-surfactant-assisted Mg-delta doping. (C) 2016 The Japan Society of Applied Physics