Effect of Size Fluctuations on the Photoluminescence Spectral Linewidth of Closely Stacked InAs Self-Assembled Quantum Dot Structures

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Abstract
We calculated the photoluminescence (PL) spectra of InAs (or InGaAs) self-assembled quantum dots for single-layer, 2-layer stacked and 3-layer stacked structures employing three models via the effective mass approximation method to clarify the effect of size fluctuations on the PL spectral linewidth. We quantitatively confirmed that the PL spectral linewidth is determined much more by height fluctuations than by diameter fluctuations. We examined the dependence of the full-width at half maximum (FWHM) on the intermediate layer thickness d for 2-layer stacked structures from d=2 nm to 6 nm to clarify the effect of vertical coupling. The FWHM increases as d decreases in regions where the potential barrier between the upper and lower islands is so thin that its fluctuations are striking, while the FWHM decreases as d decreases in regions where there is an increase in the number of directly connected islands. We explained an anomalously narrow PL spectrum of 31 meV for a 3-layer stacked structure by considering extremely reduced island height fluctuations as well as vertical coupling.