The surface of InGaAs (In 53 %) lattice-matched to InP has been phosphidized using phosphine plasma. X-ray photoelectron spectroscopy analysis indicates that substitution of phosphorus for arsenic and deposition of phosphorus layer occur due to phosphidization. Formation of indium and arsenic oxides is suppressed at the phosphidized surface of InGaAs, while phosphorus oxide is observed. Tunneling metal-insulator-semiconductor type Schottky contacts are formed on phosphidized InGaAs by evaporating various metals such as Au, Cu, Ti and Al. An effective barrier height as high as 0.7 eV is evaluated from the room temperature current-voltage characteristic for Au/InGaAs Schottky contacts. The true barrier height estimated from the Richardson plot varies depending on the metal work function.