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 Al<sub>x</sub>Ga<sub>1-x</sub>N 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.