Estimation of the location of embedded InGaAs/GaAs quantum dots by measuring strain-induced blueshift of photoluminescence

Abstract

A method was proposed to estimate the location of embedded InGaAs/GaAs quantum dots (QDs) as the distance from the center of a flat cylindrical nanoprobe of radius 600 nm, by measuring the blueshift of photoluminescence (PL) under elastic indentation of the nanoprobe onto the sample surface. The energy of the enhanced fine PL peaks originating from single QD was observed to blueshift linearly with indentation force. The PL peak energy shift per unit force, i.e., the blueshift rate, was measured in the range 22.7–87.8 meV/mN. Analyzing the nanoprobe-induced strain and energy shift of the ground state of QD, based on a numerical simulation, provided a quantitative relationship between the blueshift rate and the QD’s distance from the probe center. With this relationship, we succeeded in estimating the location of the embedded QDs from the experimentally obtained blueshift rate. The observed QDs were determined to be located around the nanoprobe edge, which coincides with the observation that only the PL emitted from the QDs located under the probe edge is enhanced and observable under nanoprobe indentation. The method presented in this paper provides a reliable and simple way to estimate the location of the embedded QDs with respect to the probe center by nanoprobe indentation.