Stoichiometric growth of high Curie temperature heavily alloyed GaMnAs

Heavily alloyed, 100 nm Ga1-xMnxAs (x > 0.1) films are obtained via low-temperature molecular beam epitaxy by utilizing a combinatorial technique which allows systematic control of excess arsenic during growth. Reproducible electronic, magnetic, and structural properties are optimized in a narrow range of stoichiometric growth conditions. In contrast to a prediction of the Zener model of hole-mediated ferromagnetism, the Curie temperature of the stoichiometric material is independent of x (for x > 0.1), while substitutional Mn content is proportional to x within a large window of growth conditions. (c) 2008 American Institute of Physics.