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Báo cáo hóa học: " Optical identification of electronic state levels of an asymmetric InAs/InGaAs/GaAs dot-in-well structure"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Optical identification of electronic state levels of an asymmetric InAs/InGaAs/GaAs dot-in-well structure | Zhou et al. Nanoscale Research Letters 2011 6 317 http www.nanoscalereslett.eom content 6 1 317 o Nanoscale Research Letters a SpringerOpen Journal NANO EXPRESS Open Access Optical identification of electronic state levels of an asymmetric InAs InGaAs GaAs dot-in-well structure Xiaolong Zhou Yonghai Chen and Bo Xu 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 Introduction Self-assembled semiconductor quantum dots QDs have attracted much attention in the past decade due to their importance in low-dimensional physics and their applications in opto-electronic devices such as lasers 1 2 detectors 3 4 and optical amplifiers 5 . The quantum dots are often formed utilizing the lattice mismatch between the substrate and the deposited materials. Strain is the driving force of this gr owth mode i.e. Stranski-Krastanow S-K mode which presents the transition from two-dimensional 2D layer to defect-free islands. With size .