Electrical Properties of Doped Germanium Nanofilms

Abstract

Dependences of the electron concentration for germanium nanofilms grown on Ge, Si, $Ge_{(0.64)}Si_{(0.36)}$ Ta $Ge_{(0.9)}Si_{(0.1)}$ substrates with crystallographic orientation (001) and doped with shallow and deep donor impurities on their thickness at T=300K were obtained on the basis of the solutions of the electroneutrality equation. The concentration of conduction electrons for the germanium nanofilms depended on the magnitude of internal mechanical strains, the concentration of the doping impurity, and its ionization energy. Increasing the concentration of the doping impurity for germanium nanofilms grown on Ge, $Ge_{(0.64)}Si_{(0.36)}$ Ta $Ge_{(0.9)}Si_{(0.1)}$ substrates leads to an increase of the electron concentration in the conduction band and a decrease of the role of quantum-dimensional effects. An increase in the ionization energy of the donor impurity leads to a decrease in the electron concentration in the conduction band of the nanofilm due to the deionization of the impurity level. The dependence of the electrical conductivity of the doped nanofilm on the value of internal mechanical strains, in contrast to the undoped nanofilm, will be largely determined by the changes in electron mobility under deformation. Therefore, the decrease in electron mobility, which is associated with the deforming redistribution of electrons with different mobility between L 1 and $\Delta_{1}$ minima of the germanium conduction band, will lead to a decrease in the electrical conductivity of the germanium nanofilm. The obtained results can be used in the modeling and synthesis of doped germanium nanofilms with the controlled electrical properties, essential, for example, for designing n-MOSFET and n-MODFET transistors, lasers on heterojunctions, electro-optical modulators.