Study of Cs adsorption on Ga(Mg)0.75Al0.25N (0 0 0 1) surface: A first principle calculation

In order to study the activation process of Ga1−xAlxN photocathodes theoretically, models of Cs adsorption on Ga(Mg)0.75Al0.25N (0 0 0 1) surface are built, then the atomic structure, electronic structure, adsorption energy, work function, dipole moment and optical properties of the models are calculated. All calculations are carried out using Cambridge Serial Total Energy Package (CASTEP) based on first principle. Results show that Cs adsorption on Mg doping Ga1−xAlxN (0 0 0 1) surface can reduce work function of the surface, and the favorite adsorption site is on the top of p-type impurity. Cs adsorption on p-type Ga1−xAlxN (0 0 0 1) surface can produce the structure of p-type bulk with n-type surface, which is helpful to surface band bend downward and decrease electron affinity seriously. The absorption coefficient of Cs adsorption system is less than that of the clean surface. Theoretical study of Cs adsorption on Ga1−xAlxN (0 0 0 1) surface can help to improve activation technology of Ga1−xAlxN photocathodes.