Low-temperature anti-Stokes photoluminescence in CdSe/ZnSe nanostructures

Abstract

Intense anti-Stokes photoluminescence was observed at low temperatures in CdSe/ZnSe nanostructures with separate CdSe inserts in a ZnSe matrix; the nominal thickness of these inserts amounted to 1.5 and 0.6 monolayers. It is shown that the intensity of an anti-Stokes band excited by the photons of energies considerably lower than the band’s peak is quadratic in the excitation power; in the case of resonance excitation, a weaker dependence is obtained. A mechanism behind the excitation of anti-Stokes photoluminescence is suggested on the basis of nonlinear two-step two-photon absorption via the deep states of the defect centers including cation vacancies localized at the barrier-nanoisland interface.