First principle research on Ga rich GaAs0.5P0.5(001) β2(4 × 2) and As(P) rich β2(2 × 4) reconstruction surfaces with and without Cs adsorption

Abstract

Based on first principle calculations, Ga rich and As(P) rich clean GaAs0.5P0.5(001) reconstruction surfaces and adsorbed surfaces with 0.125ML coverage of Cs at different sites are researched. Formation energy of Ga rich GaAs0.5P0.5(001) β2(4 × 2) reconstruction surface is smaller than that of As(P) rich one, and the work functions of Ga rich β2(4 × 2) and As(P) rich β2(2 × 4) surfaces are 4.657 eV and 5.187 eV, respectively. The adsorption energies of Cs adatoms on both surfaces are negative, showing that Cs adsorption is a stable exothermic process. The work functions of two surfaces both decrease after Cs adsorption, and the average variation of As(P) rich β2(2 × 4) surface is larger. Mulliken charge analysis shows that Cs adatoms transfer electrons to GaAsP substrate, resulting in Cs-GaAsP dipoles which lower the work functions. When Cs atoms are located at D2 of Ga rich surface and D2’ of As(P) rich surface, work function values of the two reconstruction surfaces reach the minimums, which are 2.834 eV and 2.859 eV, respectively. By calculating dipole moments, it can be found that Cs adatoms on the topmost layer form larger effective dipole moments with GaAsP substrate than the Cs atoms located in the trench.