Lattice strain measurement of strained In_0.1Ga_0.9As/GaAs heterostructures by RBS and channeling

Abstract

Organometallic Vapor Phase Epitaxy (OMVPE) grown layered structures of In_0.1Ga_0.9As/GaAs have been analyzed by He⁺⁺ ion backscattering and channeling. From the random spectrum, the In_xGa_{1 - x}As layer thickness was determined to be around 300 Å and the composition of In to be In_0.1 within an experimental error of around 5%. The χ_min obtained from the In signal is around 7% which shows that the epilayer is of good crystallinity. The normalized yield vs. the tilt angle for the epilayer and the substrate along the off-axis (along [1 1 0] direction of the substrate) shows a shift in the minimum yield χ_min dip, which is a direct measure of the strain present. This shift is found to be 0.2 ± 0.05° corresponding to a tetragonal distortion of 0.7 ± 0.2%. Shifting of the minimum yield dip of the overlayer towards left side with respect to the substrate indicates that the strain is compressive which is what is expected. X-ray diffraction is also carried out on the same sample which gives us ε ⊥=1.01% and the in-plane lattice mismatch is nearly zero.