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A numerical model based on the Green’s function formalism has been developed and used to investigate the radiative recombination processes in multiple narrow-gap semiconductor materials. Full band structures and adaptive band-dependent tetrahedral meshes were adopted to improve the accuracy of the calculation. As a validation, the spectrum of the absorption coefficient for germanium was examined, giving good agreement with the experimental data. The absorption coefficient and radiative recombination lifetime for HgCdTe were then investigated for different compositions, carrier concentrations, and operating temperatures. The results confirmed the accuracy of the widely used theoretical formula for the radiative recombination lifetime under the condition that the effective mass of holes in the formula must be carefully chosen. Based on all our comparisons and calculations, the Green’s function model is proved to be a reliable tool for predicting the radiative recombination properties of HgCdTe, which could further facilitate the investigation of more complicated processes such as photon-recycling issues.

The potential applications of germanium and its alloys in infrared silicon-based photonics have led to a renewed interest in their optical properties. In this letter, we report on the numerical determination of Auger coefficients at T = 300 K for relaxed and biaxially strained germanium. We use a Green's function based model that takes into account all relevant direct and phonon-assisted processes and perform calculations up to a strain level corresponding to the transition from indirect to direct energy gap. We have considered excess carrier concentrations ranging from 1016 cm−3 to 5 × 1019 cm−3. For use in device level simulations, we also provide fitting formulas for the calculated electron and hole Auger coefficients as functions of carrier density.

A generalized numerical model for the phonon-assisted optical interband transition based on the Green's function formalism was developed and implemented to investigate optical processes in germanium and silicon media intended for on-chip light emitter and laser applications. High-fidelity full band structures obtained from the empirical pseudopotential method, self-energies, and the corresponding spectral density functions for the phonon-perturbed electron and holes have been computed numerically as a function of strain, temperature, and doping level. Validation has been carried out by showing the model's ability to accurately reproduce the measured temperature dependent absorption coefficient data for both germanium and silicon. Absorption coefficients, radiative recombination rates of germanium and silicon active media were investigated with different biaxial tensile strain, doping concentrations and injection conditions. Furthermore, when the model is employed to compute the optical gain in strained germanium, we find that the use of tensile strain and high injection are the preferable approaches to obtain population inversion. At the same time, strong absorption from the spin-orbit to the heavy-hole band limits the maximum injection density that can be applied. Finally, when applied to study silicon, the proposed model also successfully reproduces the experimentally observed radiative recombination peak due to the two-phonon process.