We describe an in situ method for inhibiting surface roughening during the thermal removal of the GaAs native oxide layer based on a thin GaAs sacrificial film deposited on top of the native oxide layer prior to sample heating. The required thickness of the sacrificial film is calculated to be on the order of 5 nm, fitting well with experimental results. Atomic force microscopy and reflection high-energy electron diffraction indicate improvement in surface smoothness, from a root-mean-square roughness of 2.3 nm to 0.5 nm, while inhibiting the inherent pit formation commonly associated with thermal desorption. (c) 2007 The Electrochemical Society.