Abstract
Nonstoichiometric low-temperature grown (LTG) GaAs0.6Sb0.4 is epitaxially grown by molecular beam epitaxy on a lattice mismatched Al0.77In0.23As buffer layer. Ex situ annealing leads to an increase in the wafer sheet resistivity. Values as high as 1.7×108Ω∕sq were measured. By high resolution transmission electron microscopy, clusters were observed in LTG-GaAs0.6Sb0.4 after annealing, some of them attached to dislocation lines. Moreover, in a 600°C annealed sample, the clusters have two different crystal structures and a spread in cluster size is present from an early formation state up to a diameter of 12.5nm. Hence, the strain surrounding the clusters is not uniform, which leads to an asymmetry of the x-ray diffraction (XRD) peak. In addition to an increased peak asymmetry with increasing annealing temperature, the XRD peak is shifted towards higher 2θ values, resulting in a lattice constant shift of 0.24%. This lattice constant shift is due to a strain relaxation process by forming clusters.
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