The compensation of Ge pulse‐diffused into high‐purity epitaxial from a thin elemental source using rapid thermal processing has been investigated. A comparison of SIMS and differential Hall effect measurements shows that the resulting n+‐doped layers are highly compensated, with atomic Ge concentrations of 1021–1022 cm−3, but free electron concentrations of only . In contrast to the case where Ge is introduced during crystal growth or by ion implantation, donors are not compensated by acceptors when Ge is pulse‐diffused into . Photoluminescence spectroscopy shows that donors are compensated by acceptors rather than acceptors. At low diffusion temperatures, Ga vacancies are formed as Ga rapidly diffuses into the Ge layer. These Ga vacancies suppress the formation of As vacancies and, as a result, acceptors. At higher diffusion temperatures, complexes are formed more rapidly than acceptors. Low temperature Hall effect measurements suggest that these complexes are neutral. The formation of complexes, at the expense of isolated donors and acceptors, is correlated with diffusion temperatures exceeding the liquidus (∼865°C) and is explained by a dramatic increase in the concentration in the near surface region due to Ga dissolution in the Ge‐Ga‐As liquidus.