Effect of Strongly Mismatched GaAs and InAs Inserts in a InAlAs Buffer Layer on the Structural and Optical Properties of Metamorphic InAs(Sb)/InGaAs/InAlAs/GaAs Quantum-Confined Heterostructures
Metamorphic InAs(Sb)/InGaAs/InAlAs quantum-confined heterostructures with thin (1–5 nm) strongly mismatched GaAs and InAs inserts in a gradient metamorphic InxAl1−xAs buffer layer have been grown on GaAs (001) substrates by molecular beam epitaxy. It has been shown that the use of a 5-nm GaAs insert in the region of a metamorphic buffer layer at x ~ 0.37 almost doubles the photoluminescence intensity at 300 K (λ ~ 3.5 μm) from an InAs/InGaAs quantum well with a monolayer InSb insert. This is explained by an increase in the hole localization energy in InSb measured by photomodulation reflection Fourier transform infrared spectroscopy. This increase is due to increased elastic stresses in the quantum well because of a decreased density of threading dislocations in this structure caused by the introduction of an additional inverse step into the metamorphic buffer layer in the form of a 5-nm GaAs layer. The introduction of a 5-nm InAs layer into the metamorphic buffer layer violates its functions as a dislocation filter, leading to a higher density of dislocations in the quantum well region and to an order of magnitude decrease in the luminescence intensity.