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Effects of crossed states on photoluminescence excitation spectroscopy of InAs quantum dots.

Shih CI, Lin CH, Lin SC, Lin TC, Sun KW, Voskoboynikov OA, Lee CP, Suen YW - Nanoscale Res Lett (2011)

Bottom Line: 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.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.

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Affiliation: Institute of Nanoscience, National Chung Hsing University, 250 Kuo Kuang Rd,, Taichung 402, Taiwan. ysuen@phys.nchu.edu.tw.

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.

No MeSH data available.


Magnetic field dependent PLE spectra of QD1 recorded at 1.4 K from 0 to 14 T.
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Figure 6: Magnetic field dependent PLE spectra of QD1 recorded at 1.4 K from 0 to 14 T.

Mentions: For the PLE experiments, the excitation power was around 10 W/cm2 to avoid any emission from an excited state and to suppress the Auger scattering. Figure 4 shows the PLE spectrum of the QD1 sample at 1.4 K with the detection energy fixed at 1.198 eV (the maximum of the ground state transition at the same temperature). In this figure, the spectrum with the bottom horizontal axis was plotted to represent the difference between the excitation and detection energies (Eexc - Edet). At the high-energy end of the PLE spectrum, absorption occurs in the GaAs barrier layer (approximately 1.52 eV) and in the 2D InAs wetting layer (absorption transitions from both the light holes and the heavy holes). At a lower energy, only one resonance at 35 meV above the ground state was observed. However, there was no peak resolved at the energy where the first excited state absorption happens. Figure 5 shows the PLE spectra of QD1 measured with detection energies fixed at five different positions on the ground state peak. All the absorption peaks, other than 35 meV, were shifted according to the change in detection energies. The peak at 35 meV also did not change in position when the PLE spectra were measured at different magnetic fields, as shown in Figure 6. All of the evidence indicate that the peak at 35 meV indeed corresponds to the relaxation by the emission of one InAs/GaAs interface phonon [14].


Effects of crossed states on photoluminescence excitation spectroscopy of InAs quantum dots.

Shih CI, Lin CH, Lin SC, Lin TC, Sun KW, Voskoboynikov OA, Lee CP, Suen YW - Nanoscale Res Lett (2011)

Magnetic field dependent PLE spectra of QD1 recorded at 1.4 K from 0 to 14 T.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211504&req=5

Figure 6: Magnetic field dependent PLE spectra of QD1 recorded at 1.4 K from 0 to 14 T.
Mentions: For the PLE experiments, the excitation power was around 10 W/cm2 to avoid any emission from an excited state and to suppress the Auger scattering. Figure 4 shows the PLE spectrum of the QD1 sample at 1.4 K with the detection energy fixed at 1.198 eV (the maximum of the ground state transition at the same temperature). In this figure, the spectrum with the bottom horizontal axis was plotted to represent the difference between the excitation and detection energies (Eexc - Edet). At the high-energy end of the PLE spectrum, absorption occurs in the GaAs barrier layer (approximately 1.52 eV) and in the 2D InAs wetting layer (absorption transitions from both the light holes and the heavy holes). At a lower energy, only one resonance at 35 meV above the ground state was observed. However, there was no peak resolved at the energy where the first excited state absorption happens. Figure 5 shows the PLE spectra of QD1 measured with detection energies fixed at five different positions on the ground state peak. All the absorption peaks, other than 35 meV, were shifted according to the change in detection energies. The peak at 35 meV also did not change in position when the PLE spectra were measured at different magnetic fields, as shown in Figure 6. All of the evidence indicate that the peak at 35 meV indeed corresponds to the relaxation by the emission of one InAs/GaAs interface phonon [14].

Bottom Line: 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.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institute of Nanoscience, National Chung Hsing University, 250 Kuo Kuang Rd,, Taichung 402, Taiwan. ysuen@phys.nchu.edu.tw.

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.

No MeSH data available.