Mismatch and electron mobility in MBE GaxIn1−xas epitaxial layers on InP substrates

Composition inhomogeneity in nearly matched epilayers of the ternary semiconductor alloy Ga_xIn_1–xAs (x close to 0.47), grown by molecular beam epitaxy (MBE) on (001) InP substrates is correlated to variation of the lattice mismatch by x-ray imaging and local diffractometry. Misfit dislocations are shown to develop in areas of large misfit (above 2 × 10^–3) and are at the origin of a severe degradation of the electron mobility: an increase by a factor of about 4 in the intrinsic misfit (2.3 × 10^–3 compared to 0.6 × 10^–3) results in a 35 % reduction of the 77 K electron mobility.Part of this work has been done while this author was with Thomson-CSF Central Research Laboratory, Orsay, France