Study on electronic and optical properties of alkali metal atoms adsorbed GaAs nanowires by first-principles calculations

This study presents a systematic investigation on the electronic and optical properties of GaAs nanowire surfaces by adsorption of alkali metal atoms (Li, Na, K, Cs) using a first-principles approach. Calculated adsorption energies show that all alkali metal atoms prefer to adsorb on the GaAs bridge site of GaAs nanowire surface, and Na adsorbed GaAs nanowire structure is the most stable. Under the joint action of surface dipole moment and band bending region, alkali metal atoms adsorption can obviously reduce the work function of GaAs nanowire surface. All alkali metal atoms carry positive charge due to the electron transfer from adatoms to nanowire surface atoms. After alkali metal atoms adsorption, the band gap of GaAs nanowire surface is narrowed and the Fermi level enters into the conduction band, which makes nanowire surfaces exhibit n-type conductivity. The absorption coefficient curves occur red-shifted phenomenon and the highest absorption peaks are slightly decreased due to alkali metal adsorption. We believe that these calculations are suitable for experimental exploration and useful for preparing alkali metal adsorbed GaAs-based nano-optoelectronic devices.