The surface state density of gallium arsenide (GaAs) materials can be significantly lowered by surface sulfur passivation. After passivation, a 14-fold enhancement in the photoluminescence intensity of GaAs films is observed and the photocurrent and responsivity also increase. The performance improvement is analyzed from the perspective of energy bands and the results indicate that the passivation treatment is helpful for the adjustments of the surface density and the Schottky barrier height, which further improves the material performances.