X-ray diffraction and channeling-Rutherford backscattering spectrometry studies of ion implantation damage in Al_xGa_1-xAs

X-ray diffraction and channeling-Rutherford backscattering spectrometry (RBS) were employed to investigate damage accumulation in Al_xGa_1-xAs (x = 0.50, 0.75, 0.85, and 1.0) irradiated at 80 K with MeV ions. The x-ray measurements, performed both before and after warming the samples, showed a transition in the strain accumulation behavior as the Al content increased. For samples with low Al content, x = 0.50, the strain increased monotonically with fluence until the sample amorphized, a behavior similar to GaAs. For samples with x≥0.75, the strain initially increased, then plateaued, and finally diminished at high fluences. The RBS data, obtained at both 80 K and room temperature, revealed a similar dependence of the amorphization behavior upon Al content. For pure AlAs films, amorphization in the bulk was not observed even after a fluence of 2 × 10¹⁷ cm² of 1.7 MeV Ar⁺. For films with low Al content, however, the Al_xGa_1-xAs layer readily amorphized with a fluence of only 6.8×10¹⁴ cm² of 1.7 MeV Ar⁺. From these data, along with previously published information provided by transmission electron microscopy studies, a model for damage accumulation in ion irradiated Al_xGa_1-xAs is proposed.