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
Highlights
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]
We have studied the electronic structure and carrier dynamics of an InAs QDs sample capped with a 5 nm In0.15Ga0.85As quantum well (QW) layer via the temperaturedependent photoluminescence and photo-modulated reflectance
The statistic histogram can be approximated with a single Gaussian function, which agrees with the PL results
Summary
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. With size smaller than the bulk exciton Bohr radius, QDs could be viewed as a nearly zerodimensional system, and the injected carriers are confined in the discrete electronic levels. Understanding of the electronic states of QDs, which have been extensively studied experimentally and theoretically, are important issues for applications. Many interests have been concentrated on the development of InAs QDs emitting in the telecommunication
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