Electron localization in Ge/Si heterostructures with double quantum dots detected by an electron spin resonance method

Electron states in Ge/Si heterostructures with double quantum dots were studied by use of the electron spin resonance (ESR) method. It was demonstrated that the spatial localization of electrons as well as the localization in the momentum space can be controlled by the change of spacer thickness between quantum dots layers. New ESR signals, indicating the electron localization on the base edges of quantum dots, were obtained for the structures with the double layers of vertically aligned Ge quantum dots separated by a 2-nm-thick Si layer. Anisotropyofthe g factoristypicalforelectronstatesin � 100 and � 100 valleys.Straindistributioninthestructures under study makes the localization of electrons in these valleys at the base edges of quantum dots energetically favorable. The broadening of the ESR line due to electron-hole exchange interaction was detected. Theoretical estimation of the exchange interaction magnitude based on the experimental data gives J ≈ 0.1 μeV.