High-purity InP layers have been successfully grown by metalorganic chemical vapor deposition (MOCVD) using tertiarybutylphosphine (TBP) as a phosphorus source. The highest quality InP layer, which was grown at a V/III ratio of 36, a growth temperature of 600-degrees-C and a growth pressure of 760 Torr, exhibited electron mobility as high as 167 000 cm2/V s and carrier concentrations as low as 1.8 X 10(14) cm-3 at 77 K. The film quality strongly depended on the silicon content as an impurity in TBP. Electron mobility at 77 K was dependent on the silicon content, changing its value from 10 100 cm2/V s (Si content; 0.8 ppm) to 167 000 cm2/V s (Si content; < 0.03 ppm). The low-temperature (4.2 K) optical properties were also affected by silicon content as a impurity. It was found that electron mobility of 167 000 cm2/V s was the highest ever reported for InP grown by MOCVD using TBP as a phosphorus source. The quality of InP grown using TBP was equivalent to that of InP grown using phosphine (PH3).