MeV Ion Damage in III-V Semiconductors: Saturation and Thermal Annealing of Strain in GaAs and GaP Crystals

MeV ion irradiation of GaAs crystals at room temperature has shown that the lattice strain perpendicular to the sample surface saturates to ~0.47% for cut and ~0.3% for and cut crystals with zero parallel strain in all cases. In this paper, the thermal recovery behavior of the saturated strain in GaAs (100) is presented for a 15 min isochronal annealing. The recovery of strain depth profile is shown explicitly by a dynamical theory analysis of the x-ray rocking curves taken after each annealing step. The isochronal recovery behavior of strain suggests that a spectrum of activation energies is involved in the thermal migration of defects in the saturated surface layer. This also suggests that many kinds of antisite defect complexes exist in the surface layer. The strain and related defects are also shown to saturate in MeV ion bombarded GaP (100) crystals. This may indicate that all the primary defects (interstitials, vacancies, and antisite defects) saturate under MeV ion irradiation of III-V compounds, and support the proposed ion-lattice single collision model of defect production and saturation under MeV ion irradiation. The linewidths of x-ray rocking curves obtained from GaP crystals bombarded at room temperature and at ~490 K indicate that low- temperature recovery stage defects cause major crystal distortion in III-V compounds. Also presented are the isochronal annealing behaviors of lattice strain, x-ray broadening, and peak reflecting power of room temperature irradiated GaP (100) crystals