Cooling of radiative quantum-dot excitons by terahertz radiation: A spin-resolved Monte Carlo carrier dynamics model

We have developed a theoretical model to analyze the anomalous cooling of radiative quantum dot (QD) excitons by THz radiation reported by G. Yusa, [Proceedings of the 24th ICPS, Teraherz-near infrared upconversion in strain-induced quantum dots, (World Scientific, Singapore, 1999)]. We have made three-dimensional (3D) modeling of the strain and the piezoelectric field and calculated the 3D density of states of strain induced quantum dots. On the basis of this analysis we have developed a spin dependent Monte Carlo model, which describes the carrier dynamics in QDs when the intraband relaxation is modulated by THz radiation. We show that THz radiation causes resonance transfer of holes from dark to radiative states in strain-induced QDs. The transition includes a spatial transfer of holes from the piezoelectric potential mimima to the deformation potential minimum. This phenomenon strongly enhances the QD ground state luminescence at the expense of the luminescence from higher states. Our model also reproduces the delayed flash of QD ground state luminescence, activated by THz radiation even ∼1 s after the carrier generation. Our simulations suggest a more general possibility to cool the radiative exciton subsystem in optoelectronic devices.