Temperature-dependent modulated reflectance and photoluminescence of InAs-GaAs and InAs-InGaAs-GaAs quantum dot heterostructures

Optical transitions and electronic properties of epitaxial InAs quantum dots (QDs) grown with and without InGaAs strain-relieving capping layer within GaAs/AlAs quantum well (QW) are investigated. Modulated reflectance and photoluminescence spectroscopy is used to probe the QD- and QW-related interband optical transitions over the temperature range of 3-300 K. The observed spectral features in QDs are identified using numerical calculations in a framework of 8-band k . p method. It is found that covering the dots by a 5 nm-thick InGaAs layer yields the energy red-shift of ground-state transition by similar to 150 meV. Moreover, the analysis of interband transition energy dependence on temperature using Varshni expression shows that material composition of InAs QDs significantly changes due to Ga/In interdiffusion. A comparison of emission-and absorption-type spectroscopy applied for InAs-GaAs QDs indicates a Stokes shift of similar to 0.02 meV above 150 K temperature.