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Optical identification of electronic state levels of an asymmetric InAs/InGaAs/GaAs dot-in-well structure.

Zhou X, Chen Y, Xu B - Nanoscale Res Lett (2011)

Bottom Line: It is shown that the carrier transfer via wetting layer (WL) is impeded according to the results of temperature dependent peak energy and line width variation of both the ground states (GS) and excited states (ES) of QDs.Additionally, as the RTA temperature increases, the peak of PL blue shifts and the full width at half maximum shrinks.Especially, the intensity ratio of GS to ES reaches the maximum when the energy difference approaches the energy of one or two LO phonon(s) of InAs bulk material, which could be explained by phonon-enhanced inter-sublevels carrier relaxation in such asymmetric dot-in-well structure.PACS: 73.63.Kv; 73.61.Ey; 78.67.Hc; 81.16.Dn.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P,O, Box 912, Beijing 100083, People's Republic of China. zhouxl06@semi.ac.cn.

ABSTRACT
We have studied the electronic state levels of an asymmetric InAs/InGaAs/GaAs dot-in-well structure, i.e., with an In0.15Ga0.85As quantum well (QW) as capping layer above InAs quantum dots (QDs), via temperature-dependent photoluminescence, photo-modulated reflectance, and rapid thermal annealing (RTA) treatments. It is shown that the carrier transfer via wetting layer (WL) is impeded according to the results of temperature dependent peak energy and line width variation of both the ground states (GS) and excited states (ES) of QDs. The quenching of integrated intensity is ascribed to the thermal escape of electron from the dots to the complex In0.15Ga0.85As QW + InAs WL structure. Additionally, as the RTA temperature increases, the peak of PL blue shifts and the full width at half maximum shrinks. Especially, the intensity ratio of GS to ES reaches the maximum when the energy difference approaches the energy of one or two LO phonon(s) of InAs bulk material, which could be explained by phonon-enhanced inter-sublevels carrier relaxation in such asymmetric dot-in-well structure.PACS: 73.63.Kv; 73.61.Ey; 78.67.Hc; 81.16.Dn.

No MeSH data available.


Related in: MedlinePlus

Photo-modulated reflectance of the as-grown sample measured at room temperature andthe shape fitting result of the complex QW-WL structure by the Aspnes formula (red solid line). Inset shows the schematic representation of band structure of an asymmetric dot-in-well QDs structure.
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Figure 3: Photo-modulated reflectance of the as-grown sample measured at room temperature andthe shape fitting result of the complex QW-WL structure by the Aspnes formula (red solid line). Inset shows the schematic representation of band structure of an asymmetric dot-in-well QDs structure.

Mentions: where EQD is the energy of QDs states, including the GS, ES1, and ES2. The parameter a represents the activation energy ratio of hole to electron and the value we used here is 1.4, which is close to the value of 1.3 used in [20]. For the GS, the emission energy EQD at room temperature is 1.02 eV and the fitted Ea is 103 meV. So the Ec we obtained is about 1.27 eV, which is almost the same as values got from ES1(1.25 eV) and ES2 (1.26 eV). To reveal the origin of the carrier channel of such asymmetric DWELL structure, the PR measurements were performed, as shown in Figure 3. The strong signal at 1.42 eV comes from the GaAs band accompanying with series of oscillations caused by built-in electric field. The two weak peaks at the low energy regions can be attributed to the energy levels of the complex structure of In0.15Ga0.85As QW + InAs WL (bi-QW) [24,28], as illustrated in the inset of Figure 3. The experimental line shapes can be fitted according to the Aspnes formula [29]:(3)


Optical identification of electronic state levels of an asymmetric InAs/InGaAs/GaAs dot-in-well structure.

Zhou X, Chen Y, Xu B - Nanoscale Res Lett (2011)

Photo-modulated reflectance of the as-grown sample measured at room temperature andthe shape fitting result of the complex QW-WL structure by the Aspnes formula (red solid line). Inset shows the schematic representation of band structure of an asymmetric dot-in-well QDs structure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3211404&req=5

Figure 3: Photo-modulated reflectance of the as-grown sample measured at room temperature andthe shape fitting result of the complex QW-WL structure by the Aspnes formula (red solid line). Inset shows the schematic representation of band structure of an asymmetric dot-in-well QDs structure.
Mentions: where EQD is the energy of QDs states, including the GS, ES1, and ES2. The parameter a represents the activation energy ratio of hole to electron and the value we used here is 1.4, which is close to the value of 1.3 used in [20]. For the GS, the emission energy EQD at room temperature is 1.02 eV and the fitted Ea is 103 meV. So the Ec we obtained is about 1.27 eV, which is almost the same as values got from ES1(1.25 eV) and ES2 (1.26 eV). To reveal the origin of the carrier channel of such asymmetric DWELL structure, the PR measurements were performed, as shown in Figure 3. The strong signal at 1.42 eV comes from the GaAs band accompanying with series of oscillations caused by built-in electric field. The two weak peaks at the low energy regions can be attributed to the energy levels of the complex structure of In0.15Ga0.85As QW + InAs WL (bi-QW) [24,28], as illustrated in the inset of Figure 3. The experimental line shapes can be fitted according to the Aspnes formula [29]:(3)

Bottom Line: It is shown that the carrier transfer via wetting layer (WL) is impeded according to the results of temperature dependent peak energy and line width variation of both the ground states (GS) and excited states (ES) of QDs.Additionally, as the RTA temperature increases, the peak of PL blue shifts and the full width at half maximum shrinks.Especially, the intensity ratio of GS to ES reaches the maximum when the energy difference approaches the energy of one or two LO phonon(s) of InAs bulk material, which could be explained by phonon-enhanced inter-sublevels carrier relaxation in such asymmetric dot-in-well structure.PACS: 73.63.Kv; 73.61.Ey; 78.67.Hc; 81.16.Dn.

View Article: PubMed Central - HTML - PubMed

Affiliation: Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P,O, Box 912, Beijing 100083, People's Republic of China. zhouxl06@semi.ac.cn.

ABSTRACT
We have studied the electronic state levels of an asymmetric InAs/InGaAs/GaAs dot-in-well structure, i.e., with an In0.15Ga0.85As quantum well (QW) as capping layer above InAs quantum dots (QDs), via temperature-dependent photoluminescence, photo-modulated reflectance, and rapid thermal annealing (RTA) treatments. It is shown that the carrier transfer via wetting layer (WL) is impeded according to the results of temperature dependent peak energy and line width variation of both the ground states (GS) and excited states (ES) of QDs. The quenching of integrated intensity is ascribed to the thermal escape of electron from the dots to the complex In0.15Ga0.85As QW + InAs WL structure. Additionally, as the RTA temperature increases, the peak of PL blue shifts and the full width at half maximum shrinks. Especially, the intensity ratio of GS to ES reaches the maximum when the energy difference approaches the energy of one or two LO phonon(s) of InAs bulk material, which could be explained by phonon-enhanced inter-sublevels carrier relaxation in such asymmetric dot-in-well structure.PACS: 73.63.Kv; 73.61.Ey; 78.67.Hc; 81.16.Dn.

No MeSH data available.


Related in: MedlinePlus