  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
$\sim1$ s after the carrier generation. Our simulations suggest a more general
possibility to cool the radiative exciton subsystem in optoelectronic devices.
