Effect of Mn interstitials on the lattice parameter of Ga1−xMnxAs

Structural investigation of as-grown as well as annealed Ga1−xMnxAs epilayers was carried out using high-resolution x-ray diffraction (XRD) measurements for a wide range of Mn concentrations (0.027⩽x⩽0.083), with special attention on how the interstitial Mn atoms (MnI) influence the lattice parameter of this material. We observe a distinct decrease of the lattice parameter after low-temperature annealing of Ga1−xMnxAs, which is known to reduce the MnI concentration. The reciprocal space maps measured for all of the investigated samples showed that the Ga1−xMnxAs layers are fully strained—i.e., they remain pseudomorphic to the GaAs (001) substrate—for the entire thickness of the samples used (in the present case over 100 nm). In all cases studied, the XRD measurements revealed high crystalline perfection of both as-grown as well as annealed Ga1−xMnxAs epilayers.