Recombination mechanisms in 8–14-μ HgCdTe

Photoconductive measurements on n-type Hg1−xCdxTe, for compositions of 0.195 < x < 0.210, have been carried out in the temperature range 65–300°K. A comparison of the experimental data with simple band-to-band recombination theory indicates that the lifetime in the intrinsic range of temperatures is determined by an Auger limited process. The measured variation of lifetime with temperature can be used to predict values for the Auger limited lifetime in intrinsic material, τAi, over the entire temperature range 65–300°K. Calculations, using these values of τAi, for the extrinsic temperature range (<100°K) indicate that for our purer material (ND−NA≳4×1014 cm−3;μ77≳1.5×105 cm2 V−1 sec−1), the lifetime is still determined by an Auger limited band-to-band process. In somewhat more compensated material (ND−NA<4×1014 cm−3;μ77≲1.5×105 cm2 V−1 sec−1), Shockley-Read limited lifetimes are observed, although in the majority of samples measured the electron lifetime is independent of temperature. However, in some extremely highly compensated material (ND − NA < 2×1014 cm−3; μ77 < 105 cm2 V−1 sec−1), temperature-dependent lifetimes are observed below 100°K, indicating a Shockley-Read center approximately 30 meV above the valence band. Spectral response measurements indicate values of surface recombination velocity∼280 cm/sec for carefully prepared surfaces on this material.

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