Crystalline quality of low-temperature-grown InxGa1−xAs coherently grown on InP(0 0 1) substrate

Abstract

We report on the crystalline quality of low-temperature-grown (LTG) InxGa1−xAs coherently grown on InP(0 0 1) substrate using molecular beam epitaxy at a substrate temperature of 250 °C. The InxGa1−xAs was characterized using high-resolution X-ray diffraction (XRD) measurement, transmission electron microscopy (TEM), and Rutherford backscattering spectrometry (RBS). Results of 2θ/ω scan and Q-scan XRD revealed the same in-plane lattice constants for the as-grown LTG-In0.54Ga0.46As layer and the InP substrate. The results of the Q-scan indicated that the periodicity of lateral correlation length of LTG-In0.54Ga0.46As layer, which is defined by the inverse of the full width at half maximum of horizontal scan of Q-scan XRD curves, was down to around 700 nm from over 1.5 μm after annealing at 550 °C. However, in cross-sectional TEM observation, no misfit dislocations were observed in either the as-grown or annealed samples. This revealed that relatively low density of dislocations formed in both the as-grown and the annealed LTG-In0.54Ga0.46As layers. Angular RBS scans of the In signals in the as-grown and annealed LTG In0.54Ga0.46As aligned toward [1 0 0] and [1 1 0] observed deep dip curves, indicating that thermal annealing did not cause the crystalline quality of LTG In0.54Ga0.46As to noticeably deteriorate.