A surface etching effect was observed using polysulfide solution for the passivation of III-V semiconductors. The etching rate was found to be 2 Angstrom/min on InP (100). The etching effect increased surface roughness, which enhanced the adsorption of adventitious hydrocarbons and water from the ambient. Such an etching effect was not observed on the samples treated by a gas-phase polysulfide treatment. The surfaces of these samples also showed less adventitious hydrocarbons and water after exposure to the ambient. The presence of sulfide on the surface reduced the sticking coefficient of the adventitious hydrocarbons and water.