A new 2-D model for operating point shift in large LWIR HgCdTe FPA's

Bias dependence of photo-response in HgCdTe photodiodes due to series resistance

“…Although QE is supposed to be independent of bias [9], we have found that due to the presence of large series resistance, the effective QE also starts depending on bias voltage. Earlier reports on series resistance problem by Dhar [3] and Grenier [4] assume ideal diffusion limited current-voltage (I-V) characteristics model and hence could not predict the peaking behavior of the photoresponse with bias, as observed by us. In this paper, we have experimentally examined the effect of series resistance on the performance of medium wavelength infrared (MWIR) photodiodes of Hg 0.7 Cd 0.3 Te and found that for achieving highest possible QE in that particular photodiodes, there exists an optimum bias voltage.…”

“…(3)(4)(5), I 0 (x) represents that I 0 is a function of x. It is clear that I Ph cannot be extracted by simply subtracting the illuminated current and the dark current of Eqs.…”

“…Also, to keep the pitch minimum and the fill factor maximum, the common contact is taken around the periphery of the array. This necessitates the high effective series resistance in the central diodes and large resistance variation among the peripheral and the central diodes [3]. Therefore, it is important to understand the effect of series resistance on the performance of HgCdTe photodiodes.…”