Exciton emission dynamics in single InAs/GaAs quantum dots due to the existence of plasmon-field-induced metastable states in the wetting layer

A very long lifetime exciton emission with non-single exponential decay characteristics has been reported for single InA-s/GaAs quantum dot (QD) samples, in which there exists a long-lived metastable state in the wetting layer (WL) through radiative field coupling between the exciton emissions in the WL and the dipole field of metal islands. In this article we have proposed a new three-level model to simulate the exciton emission decay curve. In this model, assuming that the excitons in a metastable state will diffuse and be trapped by QDs, and then emit fluorescence in QDs, a stretched-like exponential decay formula is derived as I\left( t \right)=A\, t^\beta -1\rm e^-\left( rt \right)^\beta , which can describe well the long lifetime decay curve with an analytical expression of average lifetime \langle\tau\rangle=\frac1r\mathrm\Gamma ( \frac1\beta +1 )，where \Gamma is the Gamma function. Furthermore, based on the proposed three-level model, an expression of the second-order auto-correlation function g^2\left( t \right) which can fit the measured g^2\left( t \right) curve well, is also obtained.