Anomalous ion channeling in InGaAs/GaAs strained heterojunction

An ion beam with different incident energies E was used to analyze a 500‐Å‐thick In_0.25Ga_0.75As strained epitaxial film grown on GaAs (100) by molecular beam epitaxy. Ion channeling angular scans about 〈110〉 axis were carried out in (100) plane. When E is 5.8 MeV, the angular misalignment between 〈110〉 channels of the top layer and the substrate was 0.90°. We can calculate the planar strain of the epilayer, which is 1.62%. When incident ion energy was decreased, anomalous phemomena were observed in the angular scan profiles of the substrate. When E is 3.0 MeV, a serious asymmetry appeared in axial scan profile of the substrate; When E is 1.2 MeV, the angular misalignment reduced to 0.60°, and the critical angle for channeling of the substrate is 1.25° which is much larger than that of the epilayer, 0.95°. The physical mechanism giving rise to these phenomena is discussed, and the causes and conditions for these phenomena taking place were pointed out.