Metalorganic vapor phase epitaxy of InP prepared by a trimethylindium‐trimethylphosphine (TMIn‐TMP) adduct and PH3was first grown in a low pressure vertical reactor. The adduct with its irreplaceable merit of high stability has been successfully used in this study. The lowest carrier concentration of undoped InP epilayers is 5×1014cm−3with a 77 K mobility of 75 000 cm2/V s. The full width at half‐maximum of the 77 K photoluminescence spectrum was as narrow as 10 meV. These results can compete with all previous data from adduct sources. The growth rate was not limited by the relatively low vapor pressure of the TMIn‐TMP adduct and could reach to 8 &mgr;m/h. It suggests the high growth efficiency of this growing process.