LATTICE LOCATION OF ER IN GAAS DETERMINED FROM MONTE-CARLO SIMULATION OF ION CHANNELING SPECTRA

We have determined the lattice location of Er doped into GaAs single crystals grown by metal-organic chemical vapor deposition (MOCVD) using the ion channeling effect. A strong flux peaking is observed for 2.0 MeV He+ ions incident along the GaAs [110] axis, whereas a significant shadowing effect is seen for the [111] and [100] incidence. Monte Carlo simulation of ion trajectories has revealed that almost all Er atoms occupy the lattice position shifted by 0.6 angstrom from the tetrahedral interstitial site toward the hexagonal site. This suggests that the dopant Er atom is loosely combined with an impurity carbon atom replacing a lattice As atom. In this paper, we propose a new multistring model to simulate ion trajectories and compare it with the single row approximation in the context of accuracy and computing time.