Theory of non-equilibrium ‘hot’ carriers in direct band-gap semiconductors under continuous illumination

Abstract

The interplay between the illuminated excitation of carriers and subsequent thermalization and recombination leads to the formation of non-equilibrium distributions for the ``hot'' carriers and to heating of both electrons, holes and phonons. In spite of the fundamental and practical importance of these processes, there is no theoretical framework which encompasses all of them and provides a clear prediction for the non-equilibrium carrier distributions. Here, a self-consistent theory accounting for the interplay between excitation, thermalization, and recombination in continuously-illuminated semiconductors is presented, enabling the calculation of non-equilibrium carrier distributions. We show that counter-intuitively, distributions deviate more from equilibrium under weak illumination than at high intensities. We mimic two experimental procedures to extract the carrier temperatures and show that they yield different dependence on illumination. Finally, we provide an accurate way to evaluate photoluminescence efficiency, which, unlike conventional models, predicts correctly the experimental results. These results provide a starting point towards examining how non-equilibrium features will affect properties hot-carrier based application.

Crossover from Nonthermal to Thermal Photoluminescence from Metals Excited by Ultrashort Light Pulses

“…Indeed, under such conditions, the transient effective temperature in the Planck term grows significantly so that the thermal emission shifts from the infrared to the visible range and becomes stronger. In this case, one should interpret the emission using only the first (Planck) term in eq (as, e.g., in refs and ) and refer to the emission as thermal light emitted by an object with a time-varying temperature (see refs , , , , and ); similar behavior was observed for CW PL from a semiconductor (except, possibly, for exceptionally high CW illumination intensities), which is thus correctly referred to as “PL by thermalized systems”. , …”