Bias-dependent photocurrent of Hg1−xCdxTe photodiodes

Experimental data are presented on the bias dependence of the photocurrent of short-wave infrared n+-on-p Hg1−xCdxTe (MCT) photodiodes responding to an attenuated Nd: yttrium lithium fluoride laser, and the results are interpreted using the sweep-out theory. At high photon injection level, it is observed that the photocurrent is linearly dependent at reverse bias before saturating, and a high reverse bias is required to recover the linear response of the photocurrent to the irradiance. The conventional photocurrent model fails to explain our observations. The bias dependence is attributed to recombination of the photogenerated carriers instead of their being swept out of the depletion region, as a result of the partial cancellation of the built-in field by the spatial distribution of the high density of photogenerated electrons and holes in this region. An interpretation based upon the photoconductivity of MCT photoconductors is proposed and found to be in good agreement with the experimental results.