Photoluminescence and Time-Resolved Photoluminescence Studies of Self-Assembled InAs Quantum Dots
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Photoluminescence and Time-Resolved Photoluminescence Studies of Self-Assembled InAs Quantum Dots X. H. Zhang, J. R. Dong, and S. J. Chua Institute of Materials Research and Engineering, 3 Research Link, Singapore 117602
ABSTRACT Photoluminescence (PL) spectra and time resolved PL from self-assembled InAs/GaAs quantum dots (QDs) grown by metal organic chemical vapor deposition are studied. A reduction in the emission linewidth with increasing temperature was observed at low temperature range and an increase in the linewidth at higher temperature. It was also observed that the variation of PL peak energy with temperature does not follow Varshni's equation. These anomalous behaviors of PL can be explained in term of thermal redistribution of carriers. It was also found that the PL decay time increases with photon wavelength, which is due to the carrier transfer between laterally coupled QDs. INTRODUCTION In the past several years there has been a surge of interest in self-assembled quantum dots (QDs) fabricated by Stranski-Krastanov (SK) growth due to their importance in device applications and in understanding the fundamental physics of zero-dimensional (0D) systems [1,2]. The driving force for the formation of such QDs is the tendency to reduce the elastic energy associated with the lattice mismatch in epitaxial growth [3]. Potential applications of such QDs range from high yield lasers to single electron devices [1,2]. Quantum dot devices are expected to be superior compared to bulk and quantum well devices because of their unique properties arising from three-dimensional confinement. The self-assembled QDs have shown high radiative recombination efficiency in optical studies [4-6]. It is assumed that the broad luminescence observed after optical excitation of the QDs correspond to recombination from the ground level of inhomogeneously broadened dot ensembles or, rather, excited states as well contribute to the observed spectra [7]. However, it has been found that the growth conditions strongly influence the shape, size, and uniformity of the dot assemblages obtained. There is no complete insight into the relationship between growth conditions and the photoluminescence (PL) signature [8-10]. Furthermore, insufficient knowledge about the dot geometry, interface properties and the interaction between the dots complicate the interpretation of the PL behaviors of QDs [11,12]. In this paper, PL spectra and time resolved PL from self-assembled InAs/GaAs quantum dots (QDs) grown by metal organic chemical vapor deposition are studied. We found that the behaviors of PL and time resolved PL can be explained in terms of thermal redistribution of carriers and carrier transfer between laterally coupled quantum dots, either through the GaAs barrier or through the wetting layer. EXPERIMENTAL METHODS The InAs QDs were grown by metal organic chemical vapor deposition (MOCVD) on (100) GaAs substrates with 2ยบ miscut toward (110) direction. The typical sample structure consists of a K8.4.1 Downloaded from https://www.cambridge.org/co
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