We here report a new passivation method, with neutral sulphur, (NH4)2S, to modify the GaSb surface. The optical and
chemical properties of GaSb surface before and after neutral passivation are investigated using x-ray photoelectron
spectroscopy (XPS) and photoluminescence (PL) mapping. Neutral (NH4)2S passivation led to 20 times enhancement in
photoluminescence (PL) intensity, lower oxide content, and a less amount of elemental Sb than the untreated sample. The
passivtion effect results from the significant reduction in surface states due to the formation of Ga and Sb sulfide species.
Compared to the regular alkaline (NH4)2S treatment, surface passivation intensity and homogeneity are both improved. Our studies also indicate the neutral sulphur passivation treated surface is much more stable in air for at least 48h.