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A large scale investigation into the effects of alloy layer disorder on emission in antimonide-based superlattices is reported. The potential utility of these systems in infrared (IR) optoelectronic technologies is reviewed and issues inhibiting their realization identified. The Ga0.7In0.3Sb alloy layer is modeled using both the conventional virtual crystal approximation and models which describe microscopic disorder, clustering, and atomistic relaxation. The structures have recently been fabricated for IR laser applications and we investigate the influence of the alloy description on the emission line shapes. For each superlattice we find that the emission linewidth and peak height is very sensitive to the microscopic details of the alloy potential. Comparing the various superlattice systems, which differ regarding the InAs layer widths, we find that their linewidth values (eV) are each of the same order of magnitude for a given population of excited carriers. While values show a strong dependence on the...

We report quantitative calculations of carrier lifetimes in imperfect GaxIn1−xSb/InAs superlattice structures. A microscopic description of imperfections including substitutional anions and interface islands is obtained through a novel strain-dependent empirical pseudopotential calculation. The T matrix of scattering theory is used to take our calculations of scattering lifetimes beyond the Born approximation, including multiple scattering events. Carrier lifetimes are related to the microscopic nature of the defects, their proximity to the interfaces, and the size and shape of interface islands. Anomalous effects due to lattice relaxation are seen to alter hole lifetimes, and their dependence upon position. For isolated isovalent anion defects we predict electron and hole lifetimes as low as 0.2 and 0.8 μs, respectively, for typical defect concentrations.

Quantitative theoretical predictions of the carrier lifetimes in a number of imperfect GaxIn1−xSb–InAs superlattices are presented. Strain-dependent empirical pseudopotentials are used to provide a microscopic description of the stationary states in the structures and scattering theory is employed to extract lifetime information. The effect of interface islands is examined, and lifetimes are found to depend upon the detailed size, shape, and composition of the islands. The effect of higher order multiple scattering events is seen to be significant. For isolated isovalent Sb substitutional defects in the InAs layers, a lifetime of ≈0.4 μs is found to be typical. This is shown to be an order of magnitude shorter than in the case of As defects in the alloy layers.

The existence of localized states at InSb-like interfaces of AlSb/InAs superlattices is predicted using empirical pseudopotential calculations. These predictions are shown to be in agreement with those of ab initio pseudopotential calculations performed using the local density approximation of density functional theory, demonstrating the ability of the empirical approach to describe the microscopic features of the interface. The frequency dependence of the absorption coefficient is calculated for a series of AlSb/InAs superlattices with differing interface configurations, and the role of the interface localization in determining the optical response is identified.