The electrical and optical properties of undoped InP layers grown at low temperatures by solid source atomic layer molecular beam epitaxy are investigated. Phosphorus surface coverage during epitaxy is controlled by monitoring the evolution of reflection high‐energy electron diffraction pattern during growth. An accurate phosphorus supply by means of a valved cracking phosphorus cell is employed. The relation between phosphorus incorporation and the electronic properties of the epilayers is examined, and it is found that, at a substrate temperature of 340 °C, residual electron concentration increases linearly with phosphorus flux. Residual doping of InP layers grown at 340 °C has been reduced down to 1×1016cm−3, and Hall mobilities of 3260 cm2/V s at 300 K and 14 830 cm2/V s at 65 K are reported. Low‐temperature photoluminescence of low background doping layers is dominated by near band transitions. ©1995 American Institute of Physics.