A Failure Mode in Dense Infrared Detector Arrays Resulting in Increased Dark Current

Abstract

In this paper, we investigate a failure mode that arises in dense infrared focal plane detector arrays as a consequence of the interactions of neighboring pixels through the minority carrier profiles in the common absorber layer. We consider the situation in which one pixel in a hexagonal array becomes de-biased relative to its neighbors and show that the dark current in the six neighboring pixels increases exponentially as a function of the difference between the nominal and anomalous biases. Moreover, we show that the current increase in the six nearest-neighbor pixels is in total larger than that by which the current in the affected pixel decreases, causing a net increase in the dark current. The physical origins of this effect are explained as being due to increased lateral diffusion currents that arise as a consequence of breaking the symmetry of the minority carrier profiles. We then perform a parametric study to quantify the magnitude of this effect for a number of detector geometric parameters, operating temperatures, and spectral bands. Particularly, numerical simulations are carried out for short-, mid-, and long-wavelength HgCdTe infrared detectors operating between 77 K and 210 K. We show that this effect is most prevalent in architectures for which the lateral diffusion current is the largest component of the total dark current—high operating temperature devices with narrow epitaxial absorber thicknesses and pitches small compared to the diffusion length of minority carriers. These results could prove significant particularly for short- and mid-wave infrared detectors, which are typically designed to fit these conditions.