Back-illuminated solar-blind photodetectors for imaging applications

摘要

Back-illuminated solar-blind ultraviolet p-i-n photodetectors and focal plane arrays are investigated. We initially study single-pixel devices and then discuss the hybridization to a read-out integrated circuit to form focal plane arrays for solar-blind UV imaging. The photodetectors consist of an AlGaN p-i-n active region grown atop a high quality AlN template layer with a ～1 μm thick Al_(0.5)Ga_(0.5)N:Si-In co-doped low-resistance UV-transparent lateral conduction layer. The material is processed into a 320 x 256 array of 25 μm x 25 μm pixels using standard lithographic techniques. Typical pixels demonstrate a peak responsivity of 93 mA/W at 278 nm; this corresponds to an external quantum efficiency of 42%. The uniformity of the array is discussed, and a selection of sample images from the solar-blind focal plane array is included. In addition, recent attempts to achieve shorter wavelength deep UV back-illuminated p-i-n photodetector and focal plane arrays are also discussed.