[en] The electronic structures and optical properties of Mg₂Ge at different Al doped concentrations were calculated by using the first principle of density functional theory. Four doping models of Mg_2-xAl_xGe (x = 0, 0.125, 0.25, 0.5) were established. The calculation results show that the Al-doped Mg₂Ge Fermi level enters the conduction band and exhibits n-type conductivity characteristics. After doping, the conduction structure near the Fermi energy level of Mg₂Ge was changed to be composed of Al 3p electrons, and Ge 4s electrons and Mg 3s, 3p electrons. The static permittivity and refractive index increase. The absorption spectrum is redshifted and the maximum absorption coefficient decreases slightly. The peak value of photoconductivity is obtained when x = 0.125. The blue shift occurs in the energy loss function, and it is most obvious when x = 0.125. (authors)

[en] The electronic structure, state density, elastic constants and photoelectric properties of Mg₂Ge are calculated by using the first principle of density functional theory. The results show that Mg₂Ge is an indirect bandgap semiconductor, and the bandgap is 0.2136 eV. The valence band and conduction band are mainly composed of Ge 4s and 4p electrons, and Mg 3s, 3p and Ge 4p electrons, respectively. The static dielectric constant is 25.294, and the refractive index is 4.5043. The maximum peak value of the absorption coefficient is 396, 560.9 cm^-1. The brittleness of Mg₂Ge is explained by elastic constants. The calculated Mg₂Ge photoelectric properties and its energy band structure are analyzed, which provides theoretical basis and experimental guidance for Mg₂Ge in the field of photoelectric application. (authors)

[en] Preparation of thin films by thermal evaporation is a commonly used method that is simple to operate and may be easily scaled for industrialization. So we prepared Mg₂Ge semiconductor thin films by resistive thermal evaporation and vacuum heat treatment. First, Mg films with thicknesses of ∼460 nm were deposited on Ge(111) substrates and then annealed at 400 °C under low vacuum (10⁻¹–10⁻² Pa) in an annealing furnace. Various annealing times 3, 4, 5, 6, and 7 h were used. The structure and morphology of each film were characterized by x-ray diffraction, scanning electron microscopy, and Raman spectroscopy. The effect of annealing time on the quality of Mg₂Ge thin film growth was studied. We demonstrate that resistive thermal evaporation allows successful preparation of single-phase Mg₂Ge semiconductor thin films. We observed that with increasing annealing time, the quality of Mg₂Ge thin film first improves and then deteriorates, and for an annealing time of 5 h, this is optimized. Our results provide a reference for the preparation of Mg₂Ge semiconductor thin films. (paper)