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

Abstract

We have developed a theoretical model to analyze the anomalous cooling of radiative quantum dot (QD) excitons by THz radiation reported by Yusa et al [Proc. 24th ICPS, 1083(1998]. 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 QD's 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 QD's. 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.

Theory of the electronic structure and carrier dynamics of strain-induced (Ga, In)As quantum dots

“…Simulations [63] showed that this is a result of a THz radiation-induced charge transfer from the PEP minima to the ground DP hole state; (ii) THz radiation was experimentally found to give rise to a flash of ground-state luminescence, long after the carrier generation had been turned off. According to the theory [63], this is due to a spatial charge separation of electrons and holes, which is released by the THz excitation of holes. A brief review of the model and the main results of [63] will be given below.…”

“…The intensity of spontaneous emission can be calculated in the electric dipole approximation by summing over the partial transition rates between all electron and hole states confined to an SIQD [63]. The PL intensity, as a function of the photon energy, is then given by [37,63] …”

“…This experiment was recently analysed in terms of master equation simulations in [63]. The model of [63] is depicted schematically in figure 28.…”

“…Reference [63] was based on the following assumptions, which originate both from experiments and theoretical studies.…”

“…The radiative recombination rates of less excited PEP states were noticeably smaller than those of the DP Figure 29. (a) Experimental [137] and (b) theoretical [63] QD PL during Ar + laser pumping (--) and during simultaneous Ar + laser pumping and FEL modulation (----).…”