InP(100) surfaces were S passivated in S2Cl2, (NH4)2S and sulfide‐containing Br2solutions. After S2Cl2treatments, observations using atomic force microscopy indicated that the sample surface was rougher than the as‐received sample. Some residual oxide was also identified by Auger electron spectroscopy and x‐ray photoelectron spectroscopy analysis. Treatment of InP(100) in (NH4)2S and Br2/MeOH solutions containing trace amounts of S2Cl2and (NH4)2S significantly reduced the surface roughness of the as‐received sample. These treated surfaces were also found to be free of oxide and S passivated. These solutions therefore effectively removed the native oxide leaving substrates approaching atomic flatness and subsequently passivated surfaces with sulfur from the solution.