Solar-blind UV photodetectors based on GaN/AlGaN p-i-n photodiodes

We report on the fabrication and characterization of n-Al0.44Ga0.56N/i-Al0.44Ga0.56N/P-GaN ultraviolet solar-blind photodetectors. The diodes were fabricated by organometallic vapor phase epitaxy on low-defect-density AlGaN layers using a low-temperature interlayer technique. They present a long cutoff wavelength at 270 nm with high rejection of solar light and a responsivity of 12 mA/W. Low dark currents between 4 and 35 pA/mm(2) at -5 V have been measured. A photocurrent decay time of 14 mu s has been estimated in unbiased diodes. Due to the large dynamic resistance of the diode at 0 V bias, the detector itself shows a detectivity of 1.2 x 10(13) cm.Hz(1/2).W-1.