Truncated pyramidal-shaped InAs/GaAs quantum dots in the presence of a vertical magnetic field: An investigation of THz wave emission and absorption

Abstract

The authors report on the calculation of energy eigenvalues, transition energies, and transition dipole moments (TDMs) of truncated pyramidal-shaped InAs/GaAs quantum dots (QDs) coupled to their wetting layers (WL) under a varying and vertical magnetic field. The aim of this work is to explore a tunable source for terahertz (THz) emission and absorption through the change in dimensions and magnetic field. Through the solving the Schrodinger equation in the single-band effective mass approximation for QDs, seven initial states were extracted and the corresponding envelope functions and their changes under a magnetic field were inspected. Two groups of QDs were considered: group A of QDs, in which the height length was taken to be constant as 5nm and the base length was varied from 10 to 30nm, and group B of QDs, in which the base length was taken to be constant as 25nm and the height length was varied from 1 to 6nm. The results showed that the transition frequencies of group B of QDs lay dominantly in the terahertz region and are shifted towards lower frequencies with decreasing the height and/or increasing the magnetic field. With applying a varied magnetic field up to 25 T, a ~6THz shift in s-to-pX transition frequency was seen. Also, the polarizations of pronounced transitions were also investigated. The s-to-px, s-to-pY, and pY-to-dXY transitions were shown to be all in-plan-polarized transitions. The s-to-dXY transition is not an allowed transition.