Noise model of a-Si : H IR photodetectors

We present a noise model of a hydrogenated amorphous silicon (a-Si:H) infra red photodector, whose differential capacitance changes due to absorption o f infrared radiation in a compensated layer. The model is based on the stud y of the stochastic processes occurring in the trapping kinetics in the act ive material. Each portion of the absorber layer is assumed to be a statist ically independent noise generator, with white spectral distribution. The a mplitude of the noise generator is related to the number of thermal stimula ted transitions between defects in the forbidden gap and extended states. A fter defining the proper boundary conditions, the overall stochastic defect occupancy, the noise spectral distribution of device capacitance and its r oot mean square value are calculated. The model demonstrates that noise ari ses mainly from a limited portion of the structure. (C) 2000 Elsevier Scien ce B.V. All rights reserved.