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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.

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.


Atomic force microscopy images of (a) QD1, (b) QD2.
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Figure 1: Atomic force microscopy images of (a) QD1, (b) QD2.

Mentions: The two InAs QD samples studied in this work were grown on GaAs (001) substrates by molecular beam epitaxy. The substrate was first covered by a 200 nm GaAs buffer layer at 600°C. QDs of two different sizes were formed by depositing 2.4 and 2.6 monolayers of InAs with a growth rate of 0.056 μm/h at growth temperatures of 480°C and 520°C under As2 atmosphere, respectively. After the QDs were formed, they were then capped with a 150-nm thick GaAs Layer. QDs formed at a lower temperature (this sample is referred to as QD1 in this article) have a lens shape with a smaller average base diameter of about 20 nm and a height of 2 nm. The larger QDs (this sample is referred to as QD2 in this article) self-assembled at a higher temperature have a pyramid shape with an average base diameter of about 40 nm and a height of 14 nm. The areal densities are approximately 1 × 1011 cm-2 and 2 × 1010 cm-2 for QD1 and QD2, respectively. Figure 1a, b shows the AFM images of QD1 and QD2 samples.


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)

Atomic force microscopy images of (a) QD1, (b) QD2.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Atomic force microscopy images of (a) QD1, (b) QD2.
Mentions: The two InAs QD samples studied in this work were grown on GaAs (001) substrates by molecular beam epitaxy. The substrate was first covered by a 200 nm GaAs buffer layer at 600°C. QDs of two different sizes were formed by depositing 2.4 and 2.6 monolayers of InAs with a growth rate of 0.056 μm/h at growth temperatures of 480°C and 520°C under As2 atmosphere, respectively. After the QDs were formed, they were then capped with a 150-nm thick GaAs Layer. QDs formed at a lower temperature (this sample is referred to as QD1 in this article) have a lens shape with a smaller average base diameter of about 20 nm and a height of 2 nm. The larger QDs (this sample is referred to as QD2 in this article) self-assembled at a higher temperature have a pyramid shape with an average base diameter of about 40 nm and a height of 14 nm. The areal densities are approximately 1 × 1011 cm-2 and 2 × 1010 cm-2 for QD1 and QD2, respectively. Figure 1a, b shows the AFM images of QD1 and QD2 samples.

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.