Segregation, interface morphology, and the optical properties ofGaAs/AlAsquantum wells: A theoretical study

We investigate optical signatures of interface segregation phenomena in epitaxially grown narrow quantum wells. Short-period step formation and segregation during growth are simulated via a generalized kinetic-limited segregation model that allows for combined vertical and lateral atomic exchanges with respect to the surface. Segregation always leads to more abrupt inverted (GaAs-on-AlAs) interfaces as compared to normal (AlAs-on-GaAs) interfaces, where a wider alloy region is present. The electronic structure of quantum wells is determined in the tight-binding approach applied to supercells $\left(\sim {10}^4\hspace{0.5em}\mathrm{atoms}\right)$ with periodic boundary conditions. The atomic configurations are numerically generated according to the two-dimensional composition profiles obtained from the generalized kinetic-limited segregation model. Disorder is incorporated through an ensemble of such generated configurations, over which averaged electronic quantities are obtained. The correlation between the interface degree of roughness, alloying, and its optical properties is demonstrated. We show that segregation may improve the light-emission properties of quantum wells by reducing the roughness of stepped interfaces.