Measurement of Minority Carrier Lifetime in n-Type MBE HgCdTe on Variable Substrates

This paper correlates measurements of minority carrier lifetime using photoconductivity transient or photoconductive decay (PCD) with measurements and analysis of current–voltage ( I – V ) on P + n photodiodes of the same layer. This analysis is done at the primary temperature of operation near 77 K. Measurements of minority carrier lifetime in n -type molecular beam epitaxy Hg 1− x Cd x Te (MCT) on variable substrates of GaAs and CdZnTe are presented. The minority carrier lifetime from I – V analysis of P + n long-wave infrared (LWIR) photodiodes on CdZnTe (CZT) and GaAs substrates is similar to PCD analysis. Deviations occur for MCT/GaAs in the low-temperature extrinsic region associated with Shockley–Read–Hall (SRH) at 78 K in contrast to MCT/CZT at similar temperatures. The x -values in the formula Hg 1− x Cd x Te for samples grown on CdZnTe and GaAs are 0.22 and 0.235, respectively. I – V analysis of variable-area LWIR photodiodes shows a calculated minority carrier diffusion coefficient of 2.3 cm 2 /s on lattice-matched CZT and 3 cm 2 /s on non-lattice-matched GaAs with diffusion lengths of approximately 24 μ m and 20 μ m, respectively.