Amorphous phase formation in ion implanted InxGa1−xAs

The amorphisation kinetics of InxGa1−xAs alloys were investigated using Rutherford backscattering spectrometry in channelling configuration. Using metal organic chemical vapour deposition, epitaxial InxGa1−xAs layers were grown on either GaAs, InP or InAs over a wide range of stoichiometries. Ion implantation was then performed using 60 keV Ge ions at room temperature. In contrast with AlxGa1−xAs alloys, InxGa1−xAs does not exhibit amorphisation kinetics intermediate between the two binary extremes. The amorphisation behaviour was fit using the Hecking model yielding a determination of the relative probabilities of direct impact amorphisation (Pa) and stimulated amorphisation (As). For InxGa1−xAs, Pa is effectively independent of the stoichiometry whilst As exhibits a quadratic dependence on x with a maximum at x ≈ 0.31 (where the critical ion fluence for amorphisation is at a minimum). We attribute the rapid InxGa1−xAs amorphisation to the local strain induced by a bimodal bond length distribution, the latter demonstrated by previous EXAFS studies.