Electron-induced regrowth of isolated amorphous zones in GaAs

Electron transparent GaAs samples were implanted at 300 K and at 90 K with 50 keV Xe ions, which created small (similar to8 nm in diameter) amorphous zones in the crystalline structure. These amorphous zones were observed usi ng a transmission electron microscope (TEM). Immediately after ion implanta tion, the samples were irradiated with electrons having energies from 25 ke V to 300 keV. For all electron energies, the amorphous zones shrank and mos t eventually disappeared as the electron dose increased. The disappearance rate was independent of the ion implantation and electron irradiation tempe rature, and strongly dependent on the electron energy. As the electron ener gy was increased from 25 keV, the disappearance rate initially decreased, r eaching a minimum at an energy approximately one-half of the threshold disp lacement energy in crystalline material, and then it increased. These obser vations suggest that the mechanism responsible for inducing the crystalliza tion depends on the electron energy. (C) 2001 Elsevier Science B.V. All rig hts reserved.