Noise model of a-Si : H IR photodetectors

We present a noise model of a hydrogenated amorphous silicon (a-Si:H) infrared photodector, whose differential capacitance changes due to absorption of infrared radiation in a compensated layer. The model is based on the study of the stochastic processes occurring in the trapping kinetics in the active material. Each portion of the absorber layer is assumed to be a statistically independent noise generator, with white spectral distribution. The amplitude of the noise generator is related to the number of thermal stimulated transitions between defects in the forbidden gap and extended states. After defining the proper boundary conditions, the overall stochastic defect occupancy, the noise spectral distribution of device capacitance and its root mean square value are calculated. The model demonstrates that noise arises mainly from a limited portion of the structure. (C) 2000 Elsevier Science B.V. All rights reserved.