Relaxed InyGa1−yAs epilayers grown on (0 0 1) GaAs are known to exhibit a cross-hatched surface with ridges running along the [1 1 0] and directions. We find that Ga1−xMnxAs epilayers grown on such buffer layers can have as-grown Curie temperatures (TC) that are higher than the as-grown 110 K value typical of Ga1−xMnxAs/GaAs heterostructures. Further, low-temperature annealing leads to only modest additional increases in TC, contrasting with the behavior in Ga1−xMnxAs/GaAs where TC typically increases significantly upon annealing. Our observations suggest that the initial concentration of Mn interstitials in as-grown Ga1−xMnxAs /InyGa1−yAs heterostructures is smaller than that in as-grown Ga1−xMnxAs/GaAs heterostructures. We propose that strain-dependent diffusion may drive Mn interstitials from the bulk of the growing crystal to more benign locations on the ridged surface, providing a possible route towards defect-engineering in these materials.



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