Noise processes modeling in HgCdTe infrared photodiode detectors

Abstract

A numerical model of the current noise spectral density in elements of infrared focal plane array based on HgCdTe photodiodes has been developed. Model is based on Langevine method and applied to the photodiode with p + -n-junction and base of finite length d. Dominated dark current diffusion mechanism and random nature of thermal generationrecombination and scattering processes determined the diffusion current fluctuations has been taken into account. The model main peculiar properties are the stochastic boundary conditions on the interface between the depletion and quasineutral regions. Current noise spectral density of the diode with thin base d p , where Lp is the hole diffusion length in n-region, has been calculated. In thin base diodes with blocking contact to substrate, in which recombination velocity S = 0, a noise suppression effect is revealed. At noticeable reverse junction biases |qV| > 3kT the diffusion current noise suppression is to be observed in whole frequency band ωtfl << 1, where tfl is the hole flight time through the depletion region. In this case the diffusion current noise spectral density is less than in diodes with thick base (d >> L p ) by a factor th(d/L p ). At slight biases |qV| < 3kT the diffusion current noise suppression occurs only in limited frequency band ωτ > 1 diffusion current noise comes out of fluctuations caused by scattering processes and is independent on the diode structure. Photocurrent noise spectral density has been calculated too. Model developed is useful for the photodiode elements and arrays optimization.