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 (0.027less than or equal toxless than or equal to0.083), with special attention on how the interstitial Mn atoms (Mn-I) 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 Mn-I 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. (C) 2004 American Institute of Physics.