High-resolution XRD analysis of swift heavy ion irradiated InGaAs/GaAs heterostructures

摘要

Strain relaxation and swift heavy ion irradiation effects on molecular beam epitaxy grown InGaAs/GaAs heterostructures have been studied by high-resolution X-ray diffraction. Symmetric and asymmetric scans were analyzed to understand the irradiation effects on strain and defects. The broad layer peak of the experimental scans in the samples was observed. The excess width of the layer peak than the expected one has been attributed to the strain relaxation induced defects. Irradiated samples show an additional peak close to the substrate peak of compressive nature, which has been attributed to radiation damage in the substrate due to the heavy ions. Dynamical scattering theory based simulations have been compared with the experimental scans. It has also been used to deconvolute the additional peak. The simulation was comparable with the experimental scan and a satisfactory fit was obtained. The dislocation density has been reduced upon irradiation. The observed decrease in the defect density is attributed to the high electronic energy loss of the ions near the interface region. Also, the damage created by the heavy ions near the interface would enhance the diffusion of indium across the interface and hence reduce the relative mismatch at the interface.