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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

Photoluminescence spectrum measured at 15 K (a) and statistic histogram of aspect ratio (1 μm × 1 μm) (b) of the as-grown sample. Dashed lines in (a) present the Gaussian fitting of PL peak. Inset of (a) gives sketch of sample structure and inset of (b) gives 1 μm × 1 μm AFM image.
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Figure 1: Photoluminescence spectrum measured at 15 K (a) and statistic histogram of aspect ratio (1 μm × 1 μm) (b) of the as-grown sample. Dashed lines in (a) present the Gaussian fitting of PL peak. Inset of (a) gives sketch of sample structure and inset of (b) gives 1 μm × 1 μm AFM image.

Mentions: The sample studied in this work was grown on a 2-in. n+-GaAs (001) substrate in Riber 32p molecular beam epitaxy (MBE) system. First, a 400 nm GaAs buffer layer was grown at 600°C. Then the substrate temperature was reduced to 490°C for growth of 1.6 ML InAs. After a growth interruption of 30 s, further 0.3 ML InAs was then grown for QDs formation. After that, a 5 nm In0.15Ga0.85As + 10 nm GaAs was deposited as the low-temperature capping layer. Finally, the temperature was increased to 600°C for 500 nm GaAs capping layer. The As2 pressure was maintained at 4.6 × 10-6 Torr during the whole growth period. It is worth to note that all InAs materials were deposited at a low rate of 0.02 ML/s with a growth interruption of 10 s per 0.1 ML aiming at improving the uniformity and enlarging the size of QDs. The growth structure is illustrated in the inset of Figure 1a.


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)

Photoluminescence spectrum measured at 15 K (a) and statistic histogram of aspect ratio (1 μm × 1 μm) (b) of the as-grown sample. Dashed lines in (a) present the Gaussian fitting of PL peak. Inset of (a) gives sketch of sample structure and inset of (b) gives 1 μm × 1 μm AFM image.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Photoluminescence spectrum measured at 15 K (a) and statistic histogram of aspect ratio (1 μm × 1 μm) (b) of the as-grown sample. Dashed lines in (a) present the Gaussian fitting of PL peak. Inset of (a) gives sketch of sample structure and inset of (b) gives 1 μm × 1 μm AFM image.
Mentions: The sample studied in this work was grown on a 2-in. n+-GaAs (001) substrate in Riber 32p molecular beam epitaxy (MBE) system. First, a 400 nm GaAs buffer layer was grown at 600°C. Then the substrate temperature was reduced to 490°C for growth of 1.6 ML InAs. After a growth interruption of 30 s, further 0.3 ML InAs was then grown for QDs formation. After that, a 5 nm In0.15Ga0.85As + 10 nm GaAs was deposited as the low-temperature capping layer. Finally, the temperature was increased to 600°C for 500 nm GaAs capping layer. The As2 pressure was maintained at 4.6 × 10-6 Torr during the whole growth period. It is worth to note that all InAs materials were deposited at a low rate of 0.02 ML/s with a growth interruption of 10 s per 0.1 ML aiming at improving the uniformity and enlarging the size of QDs. The growth structure is illustrated in the inset of Figure 1a.

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