We report the preparation of GaAs substrates, using only electron cyclotron resonance plasma techniques, and the subsequent growth of GaAs by molecular beam epitaxy, accomplished within an integrated processing facility. Exposure of the substrates to a hydrogen plasma with an ion current density less than 3 mA/cm2for 1 h removes the native GaAs oxide leaving a smooth crystalline surface as revealed by streaky (1×1) reflection high energy electron diffraction patterns. At a greater ion current density a spotty diffraction pattern is obtained; a subsequent SiCl4plasma etch restores a streaky (1×1) diffraction pattern. After plasma processing, evidence of surface reconstruction is observed at substrate temperatures greater than 400 °C in an As overpressure and during GaAs overgrowth. Impurity concentrations at the epilayer/substrate interfaces of plasma‐prepared samples are found to be comparable to those of chemically prepared wet etched substrates. This vacuum substrate preparation scheme is a first step toward realizing the benefits of integrated device processing.