Influence of Internal Strain and External Pressure on Electronic States and Optical Transitions in Self-assembled InxGa1-xAs /GaAs Quantum Dots

Abstract

The room-temperature PL spectra from the self-assembled InGaAs/GaAs quantum dots (QDs) under different hydrostatic pressures have been measured. The experimental pressure coefficients (PCs) of the transitions from the ground and excited electronic states of the QDs are found to be significantly smaller than those of the InGaAs quantum well and GaAs bulk. The theoretical calculations based on the eight-band k·p theory and VFF model have been conducted to find the strain profiles and PCs of the transitions in InxGa1-xAs/GaAs pyramidal QDs under the different hydrostatic pressures. Good agreement between experiment and theory is achieved when appropriate average In content and dot size are adopted, leading to a conclusion that the smaller PCs of the QDs are mainly due to the presence of built-in strain in the QDs. Moreover, the calculations show that the increase of the In content in the dot results in the increase of the PCs.