Electronic structures and molecular doping of germanane regulated by hydrogen vacancy clusters

Abstract

Germanane is expected to substitute for existing silicon-based or germanium-based material. Germanane is regarded as an ideal candidate for next-generation semiconductor material due to its suitable band gap, high electron mobility, better environmental stability, small electrical noise and ultrathin geometry. In this work, the effects of different configuration and concentration of hydrogen vacancy cluster on the electronic properties of germanane and its molecular doping are systematically investigated through the first-principles method based on density functional theory and none-quilibrium Green’s function. The results show that the hydrogen vacancy clusters with different configurations can induce magnetism with different characteristics in Germanane_{Dehydrogenated-<i>x</i>H} (G_D-<i>x</i>H) system, and the magnetic moments are consistent with the predictions of Lieb’s theorem. Moreover, the p-type-liked doping effects caused by defective state under G_D-<i>x</i>H (<i>x</i> = 1, 4, 6) systems can be realized in their spin-down band structures. The corresponding energy values for exciting electron would gradually decrease with the increase of the concentration of hydrogen vacancy clusters under different configurations. After adsorbing tetrathiafulvalene (TTF) molecules, G/TTF and G_D-<i>x</i>H/TTF (<i>x</i> = 1, 2, 6) systems exhibit molecular doping characteristics induced by the TTF molecules. More importantly, for G_D-<i>x</i>H/TTF (<i>x</i> = 1, 6) system, the different molecular doping types can be introduced in spin-up and spin-down band structures due to the hybridization composed of molecular orbitals and defective states under spin polarization. Further calculations of their transport properties indicate that germanane-based device with Armchair and Zigzag configurations both exhibit intensive isotropy, and the performance of <i>I-V</i> characteristics can be dramatically enhanced owing to the carrier doping by TTF adsorption.