Effect of post-growth annealing on secondary phase formation in low-temperature-grown Mn-doped GaAs
by Andras Kovacs, Janusz Sadowski, Takeshi Kasama, Martial Duchamp, and Rafal Dunin-Borkowski
The microstructures of annealed GaAs layers containing 0.1%, 0.5% and 2% Mn was studied using aberration-corrected transmission electron microscopy (TEM). The layers were grown by molecular beam epitaxy at 270 °C. After heat treatment at 400, 560 and 630 °C, they are found to contain precipitate complexes of cubic or hexagonal (Mn, Ga) As, orthorhombic or rhombohedral As and voids. Information about the crystallographic structures and compositions of the phases was obtained using high-resolution TEM, scanning TEM and energy-dispersive x-ray spectroscopy. For Mn concentrations of up to 0.5%, depending on the annealing temperature, different configurations of voids and rhombohedral or orthorhombic As crystals associated with hexagonal (Mn,Ga)As nanocrystals have been indentified. For a higher Mn concentration of 2%, both cubic and hexagonal (Mn,Ga)As nanocrystals were found, but As precipitate formation was not observed. Based on experimental results a phase diagram for secondary phase formation in annealed GaMnAs layers doped with low Mn concentrations is proposed.
Andras Kovacs, Janusz Sadowski, Takeshi Kasama, Martial Duchamp, and Rafal Dunin-Borkowski: Effect of post-growth annealing on secondary phase formation in low-temperature-grown Mn-doped GaAs, J Phys D 46 (2013) 145309.