Effects of size and shape on electronic states of quantum dots
Date of Issue2006
School of Electrical and Electronic Engineering
Faculty of Engineering, Institute of Materials Research and Engineering, Singapore
A strained-modified, single-band, constant-potential three-dimensional model is formulated to study the dependence of electronic states of InAs/GaAs quantum dots QDs on shape and size variation. The QD shapes considered are i cuboid, ii cylindrical, iii pyramidal, iv conical, and v lens shaped. Size variations include i QD volume ii QD base length, and iii QD height, taking into account aspect ratio variation. Isovolume QD shapes with narrow tips were found to have higher ground-state energies than those with broad tips, and this is attributed to the smaller effective volume. The volume, base length, and height dependencies were obtained and found to tally well with both experimental results and advanced calculations. Hence, upon growth parameter variation, this can provide an alternative to confirm whether the change to the size of the uncapped QDs implies a similar change to the capped ones. Ground-state energy as function of aspect ratio does not follow a monotonic trend. Owing to the competing effect of a decrease in base length and an increase in height, the energy trend exhibits a sharp decrease to an optimum aspect ratio, followed by gentle, almost linear increase. The optimum aspect ratio varies among shapes and is predicted to be smaller for shapes with broad tips. The effective volume ratio of both shapes Veff,CUBOID/Veff,PYRAMID was determined, and found to vary with aspect ratio. Furthermore, a “cross-over” of lens-shaped QD from “lower energy” to “higher energy” group is predicted due to significant shape transition.
Electrical and Electronic Engineering
Physical review B
© 2006 The American Physical Society. This paper was published in Physical Review B and is made available as an electronic reprint (preprint) with permission of American Physical Society. The paper can be found at the following official DOI: [http://dx.doi.org/10.1103/PhysRevB.74.245331]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.