X-ray diffraction studies of GaAs implanted with 1.5 MeV Se + ions

Abstract

GaAs crystals with dislocation density smaller than 10 3 cm −2 were implanted at room temperature with 1.5 MeV Se + ions with doses ranging from 3 × 1 0 12 to 3 × 1 0 15 cm - 2 . The samples were studied with a number of X-ray diffraction methods realized using synchrotron radiation, in particular recording of rocking curves with 50 × 100 μ m 2 probe beam and with Bragg-case section topography. The strain profiles were determined by fitting the theoretical rocking curves obtained by numerical integration of the Takagi-Taupin equations. The investigation revealed two different components of ion-induced strain. For doses up to 3 × 1 0 14 cm - 2 the strain profiles were dominated by a component caused by interstitial atoms with almost constant strain close to the surface. A second component directly corresponding to the depth distribution of implanted Se atoms was observed for the higher ion doses. Crystal amorphization was not yet observed for all applied doses. The comparative studies of similarly implanted Ge crystals did not exhibit the saturation of implantation induced strain. The amorphization of Ge crystals took place for relatively small dose of 6 × 1 0 13 cm - 2 . This difference is most probably caused by increased mobility of point defects observed close to 300 K.