The molecular beam epitaxy grown metamorphic heterostructures with InAs/InGaAs quantum dots emitting in the wavelength range of 1. 55 μm were studied using structural and optical characterization techniques. These heterostructures contain In x Ga 1 – x As/GaAs (001) metamorphic buffer layers with different thickness and composition profiles. The maximum In content in the compositionally graded In x Ga 1 – x As layer was {x } = 0. 44 with its thickness varying in the range from 220 to 1100 nm. A correlation was established between the observed features in the photoreflectance and photoluminescence spectra and parameters of the metamorphic heterostructures. It is shown that the highest-energy S-shaped feature in the photoreflectance spectra is associated with transitions in the In x Ga 1 – x As inverse layer located near the structure surface. The shoulder observed in the low-temperature photoluminescence spectra on the short-wavelength side of the broad peak associated with emission from InAs/InGaAs quantum dots can be attributed to transitions from the upper part of the In x Ga 1 – x As metamorphic buffer layer.
Lakuntsova et al. (Thu,) studied this question.