Design, fabrication and characterization of high-performance AlGaN UV photodetectors

This papers discusses AlGan based photodetectors. The structures were grown by metal organic chemical vapor deposition. Spectral transmission, current-voltage (IV), and quantum efficiency (QE) measurements were performed. IV characterization of the fabricated photodetectors was carried out by using a 4142B electrometer and Keithley 6517A high resistance electrometer with low noise triax cables. QE measurements were performed using a Xenon arc lamp, monochromator, UV-enhanced fiber, and SRS lock-in amplifier. Solar blindness is guaranteed by the cut off wavelength, which is 276 nm. The I-V measurement results show that the 5 V bias dark current of a 200 μm diameter photodetector was 5 fA. This current level corresponds to the background noise floor of the electrometer that was used for the experiments, i.e. the minimum value that the electrometer can measure. The corresponding dark current density was 1.6x10-11 A/cm . The dark current at 120V was 1.6nA. The breakdown voltage of the photodetectors was measured as approximately 250 V. To the authors´ knowledge, in terms of breakdown voltage and dark current density at 5V, these values correspond to the best results for AlGaN based solar-blind p-i-n type photodetectors.