TAILIEUCHUNG - Cutting edge nanotechnology_2

Tham khảo sách 'cutting edge nanotechnology_2', kỹ thuật - công nghệ, hoá học - dầu khí phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 14 Intersublevel Relaxation Properties of SelfAssembled InAs GaAs Quantum Dot Heterostructures Jiunn-Chyi Lee and 2Ya-Fen Wu Electrical Engineering Technology and Science Institute of Northern Taiwan 2Electronic Engineering Ming Chi University of Technology Taiwan 1. Introduction The requirement for high performance optoelectronic devices has spurred much experimental effort directed toward understanding and exploiting the electronic and optical properties of quantum dots QDs . The relaxation dynamics in the zero-dimensional QD systems is expected to differ qualitatively from higher-dimensional systems since the density of states is a series of ổ-functions. The limited number of states available for carriers impairs carrier relaxation toward the ground state phonon bottleneck effect Benisty et al. 1991 Benisty 1995 Hai et al. 2006 . In addition the finite degeneracy of each QD state leads already to state filling effects when few carriers populate the lowest dot states. Both effects possibly result in intersublevel relaxation rates that are comparable to interband recombination rates and have been used to explain observed photoluminescence PL from excited states of QDs Bissiri et al. 2001 Smith et al. 2001 . The temperature dependence of PL emissions has been the subject of extensive studies for clarifying the mechanism of PL quenching processes in a randomly distributed dot structure Bafna et al. 2006 Duarte et al. 2003 Polimeni et al. 1999 . The PL spectra of QDs typically show peculiar temperature dependencies. A large temperature induced peak energy decrease which is eventually sigmoidal and a reduction of the PL full width at half maximum FWHM in mid-temperature range have been reported Dawson et al. 2005 Polimeni et al. 1999 . The phenomenon is commonly attributed to effectively redistributed carriers in QDs through the channel of the wetting layer based on a model of the temperature driven carrier dynamics which takes into account the QD size distribution .

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