Calculation of band structure of the strained germanium nanofilm, doped with a donor impurity

Abstract

Abstract The band structure of the doped germanium nanofilm grown on the G e ( x ) S i ( 1 − x ) (001) substrate was calculated on the basis of the theory of deformation potential. It was shown that internal mechanical strains exceeding 2% arise in the germanium nanofilm with increasing S i content in the substrate. The presence of such strains leads to the ( L 1 − Δ 1 ) type inversion of the absolute conduction band minimum of the nanofilm. As a result of such radical reconstruction of germanium band structure under deformation, the ionization energy of the donor dopant in the nanofilm is increasing which is explained by the increase of the effective mass of electron and, accordingly, the decrease of the characteristic size of the wave function of electron that is localized on the donor impurity. The dependence of the ionization energy of impurity on the magnitude of the internal strains is due to different values of the baric coefficients of the shift of the energy level of impurity and of the lowest conduction band minimum of the nanofilm. Obtained results can be used in design and modeling of electronic devices and sensors for modern nanoelectronics with pre-set operating characteristics on the basis of strained germanium nanofilm doped with various donors.