Accurate Prediction of Optical Transitions in Epitaxial InGaAs/InAlAs Asymmetric Coupled Quantum-Well Structures

Atomically resolved Z-contrast and strain mappings are used to extract a model of the composition of an InGaAs/InAlAs asymmetric coupled quantum-well structure grown on InP by using metal-organic vapor phase epitaxy. The model accounts for grading across multiple alloy interfaces and is used to compute intersubband absorption in the structure. The simulation accurately predicts the experimental absorption spectrum of the structure within only a few meV, an almost 10-fold improvement over simulations using a square-band profile with nominal alloy compositions. This work thus provides a significant step forward in accurate and predictive simulations of the optical properties of epitaxial heterostructures for emission, modulation, and detection in mid-infrared.