ESR Study of Electron States in Ge/Si Heterostructures with Nanodisc Shaped Quantum Dots

Abstract

Abstract Electron states in Ge/Si heterostructures with nanodisc shaped quantum dots (QDs) were studied using the electron spin resonance (ESR) method. Three ESR signals were observed under light illumination of the samples. The analysis of the angular dependences of the ESR spectra allows one performing signal assignment. Two ESR signals observed in the dark, as well as under illumination, are related to the electrons localized due to the strain at the top edges and base edges of the nanodiscs, while the third ESR signal observed only under illumination is related to the electrons localized in the Si layer above (or under) the central parts of the nanodiscs due to the Coulomb interaction with photoholes. A comparison with ESR results obtained for structures with lens-shaped QDs was performed. It was found that the nanodisc shape is crucial for the simultaneous localization of three electrons with different g values on the same QD. In the case of lens shaped QDs, only two ESR signals corresponding to the electrons localized at the QD top and base edges of QDs were observed.