Epitaxial growth of (100) GaAs on (100) silicon was achieved by excimer laser annealing of amorphous GaAs layers at 248 nm. An AlAs encapsulation layer was found to be necessary to prevent the loss of arsenic during laser annealing. An energy density of 105 mJ/cm2was the critical energy density for recrystallization. Field‐effect transistors were fabricated on the regrown (100) GaAs and resulted in a transconductance of 70–80 ms/mm.