Noise gain vs. capture probability in single quantum well infrared photodetectors at low bias voltages

A model of low frequency current noise S-l(O) is developed for single quant um well (QW) infrared photodetectors. A retarding mechanism, between subseq uent electron injections in the QW structure, might dominate under a given threshold voltage value corresponding to the inversion of the electric fiel d at the collector barrier. By considering this effect in terms of correlat ion between subsequent stochastic elementary events, the expressions of S-l (0) and of noise gain g(n), defined as S-l(0)/4eI, are deduced. In particul ar, it is found that, when the applied voltage V --> 0 and the capture prob ability p(c) --> 1, the noise gain g(n) reaches the minimum value g(n) = 1/ 4. O 2001 Elsevier Science B.V. All rights reserved.