Low-frequency noise and performance of GaN p-n junction photodetectors

We report on low-frequency noise characteristics of visible-blind GaN p-n junction photodetectors. Carrier hopping through defect states in the space charge region, believed to be associated with dislocations, is identified as the main mechanism responsible for the dark conductivity of the photodiodes. Under reverse bias, the dark current noise has the 1/f character and obeys the Hooge relation with alpha approximate to 3. Under forward bias, we observe generation-recombination noise related to a trap level with the activation energy of 0.49 eV. Under illumination, detectivity is found to be shot noise limited. The noise equivalent power of a 200x200 mu m(2) photodetector is estimated at 6.6 x 10(-15) W/Hz(1/2) at a bias of - 3 V. (C) 1998 American Institute of Physics.