Using time dependent perturbation technique, Stark shift and self-energy correction in semiconductor quantum dot are studied. The analytical results are obtained by incorporating the important excitonic and biexcitonic effects. The numerical estimations are made for potentially important II-VI semiconductor quantum dot CdS of size smaller than the bulk exciton Bohr radius. The demonstration of analytical and numerical result predicts a red shift of (Delta) E/3 with (Delta) E being the biexciton binding energy. The Stark shift and self energy correction are found to have higher amplitudes at high excitation intensities due to the presence of biexcitons.
Density matrix approach has been employed to analyze the pump-probe spectroscopic absorption spectra of small semiconductor quantum dots (QDs) under strong confinement regime with sizes smaller than the bulk exciton Bohr radius such that the Coulombic interaction energy becomes negligible in comparison to the confinement energy. The average time rate of absorption has been obtained by incorporating the radiative and nonradiative decay processes as well as the inhomogeneous broadening arising due to nonuniform QD sizes. The analytical results are obtained for QDs duly irradiated by a strong near resonant pump and broadband weak probe. Numerical estimations have been made for (1) isolated QDs and (2) QD-arrays of GaAs and CdS. The results agree very well with the available experimental observations in CdS QDs. The results in case of GaAs QDs can lead one to experimentally estimate absorption/gain spectra in the important III-V semiconducting mesoscopic structures.
Density matrix approach has been employed to analyze the pump-probe spectroscopic absorption spectra of small semiconductor quantum dots (QDs) under strong confinement regime (SCR) with sizes smaller than the bulk exciton Bohr radius such that the Columbic interaction energy becomes negligible in comparison to the confinement energy. The average time rate of absorption has been obtained by incorporating the radiative and nonradiative decay processes as well as the inhomogeneous broadening arising due to nonuniform QD sizes. The analytical results are obtained for QDs duly irradiated by a strong near resonant pump and broadband weak probe. Numerical estimations have been made for (i) isolated QDs and (ii) QD-arrays of GaAs and CdS. The results agree very well with the available experimental observations in CdS QDs. The results in case of GaAs QDs can lead one to experimentally estimate absorption/gain spectra in the important III-V semiconducting mesoscopic structures.
Density matrix approach has been employed to study analytically the absorption spectra of small semiconductor quantum dots under strong confinement regime. The results are obtained for a single quantum dot (SQD) as well as for inhomogeneous distribution of quantum dots (IQD) with Gaussian distribution of quantum dot sizes. A numerical analysis has been made for SQD and IQD of CdS crystal with data taken from recent experimental work. A negative change in the absorption coefficient occurs in the shorter pump wavelength side of the spectrum due to the biexcitonic contribution. The wavelength at which crossover from positive to negative values of the change in absorption coefficient occurs is found to depend upon both, the QD size as well as the excitation intensity. The results agree satisfactorily with the experimental observations in small CdS quantum dots.
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