Confirmation of Auger-1 Minority-Carrier Lifetimes in Hg_0.77Cd_0.23Te and Prediction of Dark Current for Long-Wave Infrared Focal-Plane Arrays

Abstract

Minority-carrier lifetime measurements have been carried out on Hg_0.77Cd_0.23Te (111)B materials with gap suitable for detection in the Long-Wave Infrared (LWIR) band. The materials were grown on top of CdZnTe substrates using a liquid-phase epitaxy (LPE) process. From measurements done at 80 K, a clear difference in terms of minority-carrier lifetimes was obtained, as expected, between p-intrinsic (≤5 ns) and n-extrinsic doped samples (420 ns). Minority-carrier lifetimes were also measured as a function of temperature for the n-type samples. Auger-1-limited lifetimes were demonstrated over a wide temperature range (from 80 K to 300 K) with negligible Radiative or Shockley–Read–Hall lifetime contributions. Predictions of dark current densities are made from those lifetime measurements, assuming an Auger-1-limited lifetime. The agreement is very good between the predictions and dark current densities measured from p-on-n 640 × 512 pixels LWIR HgCdTe focal-plane arrays with 15-μm pitch from SOFRADIR, Agreement between predicted and measured dark currents and Rule’07 for LWIR is also demonstrated herein. Finally, minority-carrier lifetime measurements are demonstrated as a predictive method for focal-plane array performance. State-of-the-art dark currents from SOFRADIR p-on-n LWIR focal-plane arrays based upon high-quality HgCdTe materials are also illustrated.