Electron spatial localization tuned by strain in Ge/Si quantum dot heterostructures

A new type of quantum dot (QD) structure that enables us to control a spatial localization of electrons by changing the strain distribution in the vicinity of QDs is proposed. The structures represent a combination of large (∼200 nm ) GeSi disklike quantum dots (nanodisks) and groups of smaller (∼30 nm ) laterally ordered QDs grown over a nanodisk template. Electron localization has been studied by the electron spin resonance (ESR) method. Analysis of experimental results has been supported by calculations of electron binding energies and carrier distribution probabilities taking into account strain effects and real geometry of nano-objects. Results show that the strain field produced by the nanodisk can be used for tuning the energy levels of electrons in different Δ valleys and makes possible successful realization of simultaneous localization of two electrons with different g factors in the vicinity of the same QD.