Theory of optical spectra of polar quantum wells: Temperature effects

Abstract

Theoretical and numerical calculations of the optical absorption spectra of excitons interacting with longitudinal-optical phonons in quasi-2D polar semiconductors are presented. In II-VI semiconductor quantum wells, exciton binding energy can be tuned on-and off-resonance with the longitudinal-optical phonon energy by varying the quantum well width. A comprehensive picture of this tuning effect on the temperature-dependent exciton absorption spectrum is derived, using the exciton Green's function formalism at finite temperature. The effective exciton-phonon interaction is included in the Bethe-Salpeter equation. Numerical results are illustrated for ZnSe-based quantum wells. At low temperatures, both a single exciton peak as well as a continuum resonance state are found in the optical absorption spectra. By constrast, at high enough temperatures, a splitting of the exciton line due to real phonon absorption processes is predicted. Possible previous experimental observations of this splitting are discussed.

Nonlinear Optical Properties in a Quantum Dot of Some Polar Semiconductors

“…[14] Numerical calculations of the optical absorption spectra of excitons interacting with longitudinal-optical phonons in II-VI polar semiconducting quantum wells have been investigated by Rodríguez. [15] The Hamiltonian of an exciton with the effect of LO phonon interaction in a polar strained semiconduc-tor, within the effective mass approximation, is given by…”