Auger recombination in narrow gap HgCdTe/CdHgTe quantum well heterostructures

We present detailed theoretical analysis of nonradiative Auger recombination in narrow-gap mercury-cadmium-telluride quantum wells (HgCdTe QWs). We suggest a microscopic model to calculate Auger recombination rates in the QWs with different Cd fraction as functions of non-equilibrium carrier density with account to the complex band dispersions and wavefunctions, degenerate carrier statistics, and screening effects. Our model is validated by the comparison of measured photoconductivity kinetics with the simulated curves. Furthermore, we use the developed calculation technique to evaluate different designs of HgCdTe/CdHgTe QWs for the far-IR emitters. In particular, we consider a series of QWs with the fixed bandgap of 40meV (lasing wavelength about 30 mu m) and find out that lasing may be favored in the QWs with moderate (6%-9%) cadmium content and not in the pure binary HgTe QWs, which is in contrast to intuitive expectations within threshold energy concept for Auger recombination. Though cadmium-free QWs do provide the highest possible Auger threshold energies, Cd-containing QWs feature much more efficient screening of Coulomb potential (and so Auger interaction) by free charge carriers. The latter effect contributes decisively into the suppression of Auger processes at low temperatures and high carrier concentrations.

Automated summary

The study provides a detailed theoretical analysis of nonradiative Auger recombination in narrow-gap HgCdTe quantum wells, proposing a microscopic model to calculate recombination rates and validating it against measurements. It evaluates different designs of HgCdTe/CdHgTe QWs for far-IR emitters, finding that moderate cadmium content in the QWs may favor lasing contrary to intuitive expectations. The efficiency of screening by free charge carriers contributes decisively to the suppression of Auger processes at low temperatures and high carrier concentrations.