An electron-hole spectrum of Ge/Si structures with Ge quantum dots: photoconductivity measurements.

The lateral photoconductivity of multilayer Ge/Si structures with Ge quantum dots (QDs) is investigated. Photoresponse in the range of 1.2-0.3 eV related to the optical transitions between QD hole levels and Si electron states is observed. It is shown that the main contribution to the lateral photoconductivity is made by the electron states localized in the Si band bending region. Application of a 'quantum box' model for the description of QD hole levels allows us to clear up the nature of peaks observed in the photoconductivity spectrum. A detailed energy scheme of the Ge/Si structures with Ge QDs is built up.