Photoluminescence observations in band-gap tailored InGaAlAs epilayers lattice matched to InP substrate

Epitaxial layers of In1−x−yGaxAlyAs with band-gap energies varying in the range 0.78 to 1.42 eV and Al mole fraction varying from 0.05 to 0.43, are grown lattice matched to InP substrate by molecular-beam epitaxy. The lattice mismatch of the independently grown epilayers is less than 0.03%. Photoluminescence in the temperature range of 4–90 K showed a characteristic ‘‘dip behavior’’ in the plot of emission energy versus temperature, which is observed for the first time to disappear in layers with Al mole fraction less than 0.22. This anomaly is postulated to originate from the onset of multiple competing transitions and exciton localization.