Dense Array Effects in SWIR HgCdTe Photodetecting Arrays

Abstract

This paper presents results from three-dimensional quantitative modeling on dense, moderately doped [ND (NA) = 5 × 1015 cm−3] short-wave infrared (SWIR) p+n and n+p Hg1−xCdxTe double planar heterostructure photodetecting arrays with absorber x = 0.451 and cap x = 0.55. At uniform reverse bias, the competition for minority carriers between closely spaced diodes preserves densities below equilibrium levels throughout the absorber. This carrier suppression has several consequences in addition to suppressing dark current by constraining the minority-carrier gradients at each diode junction. First, the dense arrays maintain volume-average negative net radiative recombination rates (negative luminescence) roughly an order of magnitude larger than comparably biased isolated diodes. Second, the negative excess minority-carrier densities suppress the volume-average net Auger recombination rate by roughly an order of magnitude in dense n-type HgCdTe arrays compared with a single diode. Third, the long minority electron diffusion lengths in the p-type HgCdTe absorber not only suppress lateral diffusion currents, but do so in a manner that provides negative differential resistance. By suppressing intrinsic recombination rates, or lateral diffusion currents, each effect can contribute to increasing R0A products in SWIR HgCdTe dense arrays. These effects should be considered when optimizing device structures for pitch, thickness, feature size, doping, and bias points.