Altering the Optical Properties of GaAsSb-Capped InAs Quantum Dots by Means of InAlAs Interlayers

In this work, we investigate the optical properties of InAs quantum dots (QDs) capped with composite In(0.15)Al(0.85)As/GaAs(0.85)Sb(0.15) strain-reducing layers (SRLs) by means of high-resolution X-ray diffraction (HRXRD) and photoluminescence (PL) spectroscopy at 77 K. Thin In(0.15)Al(0.85)As layers with thickness t = 20 Å, 40 Å, and 60 Å were inserted between the QDs and a 60-Å-thick GaAs(0.85)Sb(0.15) layer. The type II emissions observed for GaAs(0.85)Sb(0.15)-capped InAs QDs were suppressed by the insertion of the In(0.15)Al(0.85)As interlayer. Moreover, the emission wavelength was blueshifted for t = 20 Å and redshifted for t ≥ 40 Å resulting from the increased confinement potential and increased strain, respectively. The ground state and excited state energy separation is increased reaching 106 meV for t = 60 Å compared to 64 meV for the QDs capped with only GaAsSb SRL. In addition, the use of the In(0.15)Al(0.85)As layers narrows significantly the QD spectral linewidth from 52 to 35 meV for the samples with 40- and 60-Å-thick In(0.15)Al(0.85)As interlayers.