Theoretical calculation of electron transport properties of atomic chains of (GaAs)n (n=1-4)

Abstract

Electron transport properties of the (GaAs)n(n=1-4) linear atomic chains, which are sandwiched between two infinite Au(100)-33 leads, are investigated with a combination of density functional theory and non-equilibrium Greens function method from first principle. We simulate the Au-(GaAs)n-Au nanoscale junctions breaking process, optimize the geometric structures of four kinds of junctions, calculate the cohesion energies and equilibrium conductances of junctions at different distances. The calculation results show that there is a stable structure for each nanoscale junction. The average bond-lengths of Ga-As in each chain at equilibrium positions for stable structure are 0.220 nm, 0.224 nm, 0.223 nm, 0.223 nm, respectively. The corresponding equilibrium conductances are 2.328G0, 1.167G0, 0.639G0, and 1.237G0, respectively. It means that each of all the junctions has a good conductivity. We calculate the transmission spectra of the all the chains. With the increase of atomic number in the (GaAs)n (n=1-4) chains, there appears no oscillation phenomenon for the equilibrium conductance. We calculate the projected densities of states of all nanoscale junctions at equilibrium positions, and the results show that electronic transport channel is mainly contributed by the px and py orbital electrons of Ga and As atoms. In the voltage range of 0-2 V, we calculate the current-voltage characteristics of junctions at equilibrium positions. With the increase of external bias, the current increases, and the I-V curves of junctions show linear characteristics for the (GaAs)n (n=1-3) atomic chains. However, there appears a negative differential resistance phenomenon in each of the voltage ranges of 0.6-0.7 V and 0.8-0.9 V for the (GaAs)4 linear atomic chain.