Pyrolysis of high‐purity digermane (Ge2H6) has been used to grow epitaxial Ge films of high crystalline quality on (100) GaAs substrates in a low‐pressure environment. X‐ray double‐crystal diffractometry shows that fully commensurate, coherently strained epitaxial Ge films can be grown on (100) GaAs at digermane partial pressures of 0.05–40 mTorr for substrate temperatures of 380–600 °C. Amorphous films also were deposited. Information about the crystalline films surface morphology, growth mode, and microstructure was obtained from scanning electron microscopy, cross‐section transmission electron microscopy, andinsitureflectivity measurements. The amorphous‐to‐crystalline transition temperature and the morphology of the crystalline films were both found to depend on deposition conditions (primarily the incidence rate of Ge‐bearing species and the substrate temperature). Epitaxial growth rates using digermane were found to be about two orders of magnitude higher than rates using germane (GeH4) under similar experimental conditions.