The fabrication of a 128×128 solar-blind AlGaN p-i-n back-illuminated ultraviolet photodetector array

128×128 pixels AlGaN solar blind ultraviolet photodetector arrays have been designed and fabricated. The diameter of each pixel is 44μm with a 50μm pitch. They are photosensitive in the waveband of 225~255nm, with the peak sensitivity at 246nm. The back-illuminated p-i-n heterojunction structure has been grown on transparent sapphire substrate using MOCVD, the aluminum composition of AlxGa1-xN n-type window layer was 71%, and the alloy composition of the unintentionally doped (UID) absorber layer was 52%. The dark current measured at a bias voltage close to zero is 27 pA, and the photocurrent is 2.7 nA at the incidence optical power of 0.12 mW in a wavelength of 246 nm, corresponding to a peak responsivity of 23mA/W.