Phosphorus atomic layer doping (P-ALD) in Ge is investigated at temperatures between 100 degrees C and 400 degrees C using a single wafer reduced pressure chemical vapor deposition (RPCVD) system. Hydrogen-terminated and hydrogen-free Ge (1 0 0) surfaces are exposed to PH3 at different PH3 partial pressures after interrupting Ge growth. The adsorption and reaction of PH3 proceed on a hydrogen-free Ge surface. For all temperatures and PH3 partial pressures used for the P-ALD, the P dose increased with increasing PH3 exposure time and saturated. The saturation value of the incorporated P dose at 300 degrees C is similar to 1.5 x 10(14) - cm(-3), which is close to a quarter of a monolayer of the Ge (1 0 0) surface. The P dose could be simulated assuming a Langmuir-type kinetics model with a saturation value of N-t = 1.55 x 10(14) cm(-2) (a quarter of a monolayer), reaction rate constant k(r) = 77 s(-1) and thermal equilibrium constant K = 3.0 x 10(-2) Pa-1. An electrically active P concentration of 5-6 x 10(19) cm(-3), which is a 5-6 times higher thermal solubility of P in Ge, is obtained by multiple P spike fabrication using the P-ALD process. (C) 2013 Elsevier Ltd. All rights reserved.