RISS 검색 - 국내학술지논문

1
State filling dependent luminescence in hybrid tunnel coupled dot-well structures.

Mazur, Yuriy I,Dorogan, Vitaliy G,Ware, Morgan E,Marega, Euclydes,Benamara, Mourad,Zhuchenko, Zoryana Ya,Tarasov, Georgiy G,Lienau, Christoph,Salamo, Gregory J RSC Pub 2012 Nanoscale Vol.4 No.23
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A strong dependence of quantum dot (QD)-quantum well (QW) tunnel coupling on the energy band alignment is established in hybrid InAs/GaAs-In(x)Ga(1-x)As/GaAs dot-well structures by changing the QW composition to shift the QW energy through the QD wetting layer (WL) energy. Due to this coupling a rapid carrier transfer from the QW to the QD excited states takes place. As a result, the QW photoluminescence (PL) completely quenches at low excitation intensities. The threshold intensities for the appearance of the QW PL strongly depend on the relative position of the QW excitonic energy with respect to the WL ground state and the QD ground state energies. These intensities decrease by orders of magnitude as the energy of the QW increases to approach that of the WL due to the increased efficiency for carrier tunneling into the WL states as compared to the less dense QD states below the QW energy.
2
Low-Density Quantum Dot Molecules by Selective Etching Using in Droplet as a Mask

Jihoon Lee,Wang, Z M,Hirono, Y,Dorogan, V G,Mazur, Y I,Eun-Soo Kim,Sang-Mo Koo,Seunghyun Park,Sangmin Song,Salamo, G J IEEE 2011 IEEE TRANSACTIONS ON NANOTECHNOLOGY Vol.10 No.3
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We demonstrate low-density quantum dot molecules (QDMs) by selective etching using In droplets as a mask. Selective etching is performed with InGaAs QDMs buried underneath GaAs capping layer, on which In droplets are formed by droplet epitaxy using molecular beam epitaxy. During the chemical etching, the droplets act as a mask and QDMs underneath the droplets that only survive. Photoluminescence measurement from the selectively etched QDMs in mesa structures shows a much reduced intensity, which indicates low-density QDMs. This technique provides a simple and flexible method to attain low-density QDMs. The density can be easily modified by the control of the size and density of In droplets, which is suitable for single QDM spectroscopy and for their device applications.
3
Effects of rapid thermal annealing on the optical properties of strain-free quantum ring solar cells

Wu, Jiang,Wang, Zhiming M,Dorogan, Vitaliy G,Li, Shibin,Lee, Jihoon,Mazur, Yuriy I,Kim, Eun Soo,Salamo, Gregory J Springer 2013 Nanoscale research letters Vol.8 No.1
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Strain-free GaAs/Al0.33Ga0.67As quantum rings are fabricated by droplet epitaxy. Both photoresponse and photoluminescence spectra confirm optical transitions in quantum rings, suggesting that droplet epitaxial nanomaterials are applicable to intermediate band solar cells. The effects of post-growth annealing on the quantum ring solar cells are investigated, and the optical properties of the solar cells with and without thermal treatment are characterized by photoluminescence technique. Rapid thermal annealing treatment has resulted in the significant improvement of material quality, which can be served as a standard process for quantum structure solar cells grown by droplet epitaxy.
4
InGaAs quantum dot molecules during selective etching using an In droplet mask

Lee, Jihoon,Wang, Zhiming,Hirono, Yusuke,Kim, Eun-Soo,Koo, Sang-Mo,Dorogan, Vitaliy G,Mazur, Yuriy I,Song, Sangmin,Park, Gamyoung,Salamo, Gregory J Institute of Physics [etc.] 2011 Journal of Physics. D, Applied Physics Vol.44 No.2
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We investigated the optical transition of InGaAs quantum dot molecules (QDMs) during selective etching of GaAs using In droplets to demonstrate low-density QDMs. During the selective etching, In droplets act as nanoscale masks and only QDMs underneath the droplets survive, by which process low-density QDMs are fabricated. The thickness of selective GaAs etching is systematically varied and a gradual red-shift is observed with the increased etching thickness. The continuing red-shift can be explained by the strain relaxation due to GaAs etching. This technique to achieve low-density QDMs by selective etching using droplets as nanoscale mask is a simple and flexible approach. This study can find applications in single QDM spectroscopy and other spectroscopic techniques.

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