We demonstrate that an amorphous As layer deposited as protection on a GaAs(001) surface grown by molecular beam epitaxy can be removed via reductive etching in an electrolytical cell at sufficiently negative electrode potentials. Employing a specially constructed electrochemical cell filled withH2SO4,we monitored the stripping process of the 50 nm As cap over a period of hoursin situwith x-ray diffraction. Our results suggest that, using this potential controlled stripping, smooth and well ordered GaAs(001) surfaces can be obtained in an aqueous electrolyte. ©1997 American Institute of Physics.