Recombination mechanisms in 8–14-μ HgCdTe

Abstract

Photoconductive measurements on n‐type Hg_1−xCd_xTe, 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, τ_Ai, over the entire temperature range 65–300°K. Calculations, using these values of τ_Ai, for the extrinsic temperature range (<100°K) indicate that for our purer material ${\mathrm{(N}}_D{\mathrm{-N}}_A{\text{≳4×10}}^{14}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}{\mathrm{;\mu }}_{77}{\text{≳1.5×10}}^5\hspace{0.17em}{\mathrm{cm}}^2\hspace{0.17em}{\mathrm{V}}^{\text{−1}}\hspace{0.17em}{\sec }^{\text{−1}}\mathrm{),}$ the lifetime is still determined by an Auger limited band‐to‐band process. In somewhat more compensated material ${\mathrm{(N}}_D{\mathrm{-N}}_A{\text{<4×10}}^{14}\hspace{0.17em}{\mathrm{cm}}^{\text{−3}}{\mathrm{;\mu }}_{77}{\text{≲1.5×10}}^5\hspace{0.17em}{\mathrm{cm}}^2\hspace{0.17em}{\mathrm{V}}^{\text{−1}}\hspace{0.17em}{\sec }^{\text{−1}}\mathrm{),}$ 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 (N_D − N_A < 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.