Impact of residual gas on the optoelectronic properties of Cs-sensitized In_0.53Ga_0.47As (001) surface

Near-infrared In_xGa_1-xAs photocathode with better optoelectronic properties is a good candidate for low-light-level (LLL) night-vision system. However, the residual gases in the ultra-high vacuum (UHV) system inevitably affects the stability and photo-emission performance of LLL photoelectric devices such as their quantum efficiency and life-time. In this study, the first-principles calculations were used to investigate the adsorption effect of five different residual gas species, including H₂, CH₄, CO, H₂O and CO₂ on Cs-sensitized In_0.53Ga_0.47As (001) β₂ (2 × 4) surface. The study results indicate that CO₂ gas molecule is the most easily attached to the Cs-sensitized surface. The adsorption of residual gases leads to the formation of a new dipole pointing from inner Cs atoms to gas molecules. It makes the charge center of the adsorbates escape from the surface, which weakens the interaction between the inner Cs atoms and the clean surface. This results in the increase of the surface work function and degradation of the performance of photoelectric devices. Also, the adsorption of residual gas molecules influences the absorption and reflection coefficients of Cs-sensitized In_0.53Ga_0.47As (001) β₂ (2 × 4) surface.