Y. Kido et al., IMPACT-PARAMETER DEPENDENT STOPPING POWERS FOR AXIALLY CHANNELED AND SEMICHANNELED MEV HE IONS IN GAAS-ER, Physical review. B, Condensed matter, 49(20), 1994, pp. 14387-14396
We have investigated the impact-parameter dependence of stopping power
s for axially channeled and semichanneled MeV He ions in Er-sheet-dope
d GaAs epitaxial layers grown by molecular-beam epitaxy. Ion channelin
g analysis using 2.0 MeV He+ coupled with the observation by transmiss
ion-electron microscope has revealed the formation of fine ErAs cluste
rs, whose lattice constant shrinks and coincides exactly with that of
the GaAs host. Thus the Er atoms take the position corresponding to th
e tetrahedral interstitial site of the GaAs lattice. The Er peak energ
ies in the backscattering spectra strongly depend on the impact-parame
ter dependent stopping powers, in particular for the incidence along [
110] and the directions slightly tilted from [110] and [100]. We divid
e the stopping power into two parts-contributions from outer electrons
and from inner electrons of GaAs. The former is calculated from the d
ielectric response theory. For the latter, we consider four types of s
topping powers dependent upon impact parameter; (1) Dettmann-Robinson
theory, (2) the binary-encounter model, (3) the binary encounter combi
ned with the local-density approximation, and (4) the extended-local-e
lectron-density model. The Er peak energies observed are well reproduc
ed employing model (3).