Reduction of defects and inhomogeneous strain in heteroepitaxial ZnSe

We present low-temperature ZnSe photoluminescence spectra having very narrow bound exciton linewidths (0.55 meV), which demonstrate for the first time that thin, pseudomorphic ZnSe layers with minimal inhomogeneous strain can be grown directly on GaAs by molecular beam epitaxy. Similar characterization of ZnSe/AlAs/GaAs heterostructures shows that AlAs layers up to 4 μm thick exhibit only kinetically limited, partial lattice relaxation, which prevents the overgrowth of uniform, coherently strained ZnSe layers. However, pseudomorphic ZnSe/AlAs/GaAs structures with thin (≲0.5 μm) AlAs layers exhibit the narrowest bound exciton peaks (≲0.37 meV full width at half maximum) ever reported for heteroepitaxial ZnSe, indicating a high degree of structural perfection.