Radiative lifetimes of excitons in semiconductor quantum dots

Abstract

A theory of intrinsic radiative lifetimes of excitons in semiconductor quantum dots is presented. Simple closed-form expressions for the decay times are obtained for quantum dots fabricated from quasi-two-dimensional systems. In particular, the intrinsic temperature-dependent photoluminescence decay time of excitons in quantum dots is found to be linear in temperature above ∼ 1 K with a positive intercept extrapolated to zero temperature, in contrast to the case of quantum wells where the extrapolated intercept is zero. Otherwise, the slope is the same as expected for quantum wells (∼17 ps K -1 for 100-Å GaAs/AlAs quantum wells). This constant offset is due to a finite spatial phase-coherence effect and is largest for quantum dots for which the lateral spatial extent is small compared with the wavelength of light in the medium corresponding to the optical transition.