Suppression of the photoluminescence quenching effect in self-assembled In As ∕ Ga As quantum dots The in-plane photoconductivity and photoluminescence are investigated in quantum dot-chain InGaAs/GaAs heterostructures. Different photoconductivity transients resulting from spectrally selecting photoexcitation of InGaAs QDs, GaAs spacers, or EL2 centers were observed. Persistent photoconductivity was observed at 80 K after excitation of electron-hole pairs due to interband transitions in both the InGaAs QDs and the GaAs matrix. Giant optically induced quenching of in-plane conductivity driven by recharging of EL2 centers is observed in the spectral range from 0.83 eV to 1.0 eV. Conductivity loss under photoexcitation is discussed in terms of carrier localiza-tion by analogy with carrier distribution in disordered media. V C 2014 AIP Publishing LLC.
Electronic and optical properties of InAs/GaAs nanostructures grown by the droplet epitaxy method are studied. Carrier states were determined by k·p theory including effects of strain and In gradient concentration for a model geometry. Wavefunctions are highly localized in the dots. Coulomb and exchange interactions are studied and we found the system is in the strong confinement regime. Microphotoluminescence spectra and lifetimes were calculated and compared with measurements performed on a set of quantum rings in a single sample. Some features of spectra are in good agreement.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-016-1518-2) contains supplementary material, which is available to authorized users.
We studied the multilayering effects of InGaAs quantum dots (QDs) on GaAs(731), a surface lying inside of the stereographic triangle. The surfaces after stacking 16 InGaAs layers were characterized with highly non-uniformity of QD spatial distribution. The bunched step regions driven by strain accumulation are decorated by QDs, therefore GaAs(731) becomes a good candidate substrate for the growth of QD clusters. The unique optical properties of the QD clusters are revealed by photoluminescence measurements. By adjusting the coverage of InGaAs, a bamboo-like nanostructured surface was observed and the quantum dots aligned up in clusters to separate the "bamboo" into sections.
Utilizing the naturally curved surface contours provided by oval defects on a GaAs(100) surface, we demonstrate that alignment of quantum-dot chains formed during the growth of (In,Ga)As multilayers is unyielding to a modest deviation of surface orientation from (100) of about 0.7° along [01-1] and 8° along [011]. This finding suggests that the strain-driven kinetic anisotropy responsible for the formation of the quantum dot chains dominates over selective island formation at steps due to surface misorientation. The robustness of the quantum dot chain adds to its potential for its future application.
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