Regulation of structural, electronic, and transport properties of single hydrogen vacancy germanane by strain

The regulation of the electronic structure and transport properties of single-hydrogen-vacancy germanane by biaxial strain is investigated using first-principles calculations based on density functional theory in this work. The results reveal that the introduction of single-hydrogen-vacancy defect states not only induces P-type doping-like effects in germanane but also triggers off a transition from non-magnetic to ferromagnetic states. Under –3% to 3% biaxial strain, both the structural parameters (bond length, bond angle, and corrugation height) and the bandgap of single-hydrogen-vacancy germanane linearly vary with strain. The P-type doping-like effect disappears at <i>ε</i> = 0.75%, while an N-type doping-like effect appears when strain increases to <i>ε</i> = 2.5%. Mechanism analysis reveals that biaxial strain primarily modulates the energies of the Fermi level, valence band maximum, and conduction band minimum, causing the relative position of defect state energy levels to shift, making them become acceptor or donor energy levels, and producing doping effect changes regulated by biaxial strain. Transport property calculations further demonstrate that the isotropic <i>I</i>-<i>V</i> characteristics and electron effective mass of single-hydrogen-vacancy germanane can be linearly controlled by biaxial strain, leading to corresponding changes in electron mobility. At <i>ε</i> = 3%, the electrical conductivity and electron mobility of single-hydrogen-vacancy germanane increase significantly to 3660 S/cm and 24252 cm<sup>2</sup>/(V·s), respectively.