Stoichiometric growth of high Curie temperature heavily-alloyed GaMnAs*

Previous work indicates that single-phase, high-Mn incorporation ($\ge $9{\%}) in GaAs can be obtained via MBE at very low substrate temperatures with film thicknesses on the order of a few nanometers. Here we present the properties of smooth, single-crystalline GaMnAs samples with Mn densities between 9 and 18{\%} and continuously tuned arsenic stoichiometry using a combinatorial, non-rotated growth method.[1] Systematic, reproducible thick films (100 nm) display optimal magnetic, electronic, and structural properties in a narrow band of As:Ga flux ratios at the stoichiometric condition, where the Curie temperature is maximum. Post-growth annealing increases the Curie temperature while lowering the lattice constant, indicating that Mn interstitials are the dominant compensating defect in high-Mn containing GaMnAs. Curie temperatures from many samples grown with varying conditions all reach a maximum near the previously reported maximum ($\sim$165K). \newline [1] R. C. Myers\textit{ et al.}, Physical Review B 74, 9 (2006).