Abstract
In this report, the influence of the intrinsic transitions between bound-to-delocalized states (crossed states or quasicontinuous density of electron-hole states) on photoluminescence excitation (PLE) spectra of InAs quantum dots (QDs) was investigated. The InAs QDs were different in size, shape, and number of bound states. Results from the PLE spectroscopy at low temperature and under a high magnetic field (up to 14 T) were compared. Our findings show that the profile of the PLE resonances associated with the bound transitions disintegrated and broadened. This was attributed to the coupling of the localized QD excited states to the crossed states and scattering of longitudinal acoustical (LA) phonons. The degree of spectral linewidth broadening was larger for the excited state in smaller QDs because of the higher crossed joint density of states and scattering rate.
Highlights
Self-assembled semiconductor nanostructures with three-dimensional carrier confinement provide the ultimate quantum system with discrete energy levels that can be tailored and controlled to tune the electrical and optical properties of these nanostructures
For the dots with a larger diameter (QD2), there are three excited states contributed to the PL spectrum at 86, 161, and 213 meV above the ground state other than the emission peaks from the barrier and the WL
At the high-energy end of the photoluminescence excitation (PLE) spectrum, absorption occurs in the GaAs barrier layer and in the 2D InAs wetting layer
Summary
Self-assembled semiconductor nanostructures with three-dimensional carrier confinement provide the ultimate quantum system with discrete energy levels that can be tailored and controlled to tune the electrical and optical properties of these nanostructures. Near-field photoluminescence excitation (PLE) spectra of single quantum dots display 2D-like continuum states and a number of sharp lines between a large zero-absorption region and the 2D wetting layer edge [5].
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