Abstract
Reflectance spectra are studied for both symmetric and asymmetric double-quantum-well structures separated by intermediate barriers with various thicknesses. It is shown that the interwell couplings versus the tunneling of the carriers across the barrier has a significant influence on the optical transition properties. Quantitative analyses are presented, which help to identify a number of transitions involving excited states, in asymmetric double wells. A theoretical model agrees with experimental results in several aspects: the interband transition energies, the transition probabilities, and the broadening of the reflectance structures. The effects of interfacial roughness and alloy disorder, in both symmetric and asymmetric systems, are carefully analyzed, which provides a new insight into the broadening of the optical transitions, due to interfacial morphology.