Alternate injections of triethylindium (TEI) and tertiarybutylphosphine (TBP) without precracking were used to realize self-limiting growth of an InP layer on a (001) InP substrate in ultrahigh vacuum. Self-limiting growth, in which the growth rate is independent of the injection time and the pressure of TEI and TBP, was achieved at a growth temperature as low as 320 degrees C. The growth rate of around 0.75 ML per cycle in self-limiting growth was assumed to be due to stable surface reconstruction of (2 X 4)-beta. A specular surface morphology was obtained in the self-limiting growth condition. By analyzing the limitation of the growth rate as well as the surface morphology of the layer, self-limiting mechanisms were proposed with respect to suppression of the-TEI decomposition on the indium surface during TEI injection, suppression of the phosphorus dissociation from the InP surface during TBP evacuation, and complete reaction between TEI and TBP during TBP injection. The growth condition range for self-limiting growth was expanded with the increase in TBP dosage which was defined as the multiplication of injection time and injection pressure.