We study the changes in electronic properties of Si-doped GaAs epilayers exposed to a hydrogen plasma and then submitted to electron beams of 20 keV injection energy. Using Hall-effect measurements, we have observed the formation of Si–H complexes and their dissociation due to the electron-beam irradiation. As this last effect increases the conductivity of the epilayer, we have been able to fabricate, with an electron-beam lithography system, various conductive microstructures. Characterizations have been achieved by cathodoluminescence (CL) imaging. Actually, due to the CL reading method which has been used, we have only fabricated micronic-size structures. However, taking into account the high spatial resolution of electron-beam writing, such a process could, possibly, be used as a way of fabrication of mesoscopic structures. © 2000 American Institute of Physics.