Preparation and Properties of Diluted Magnetic Semiconductors GaMnAs by Low-Temperature Molecular Epitaxy

GaMnAs films are prepared by low-temperature molecular beam epitaxy. Based on the experimental results, the influence of growth and annealing conditions on the physical properties and defect configurations is discussed. In particular, the major compensating defects, such as As antisite (As_Ga) and Mn interstitials (Mn_I), are studied in detail. Thereby, the relationship between structure and magnetic properties is given. It is indicated that a higher annealing temperature can remove Mn_I out of the GaMnAs lattices so as to raise the Curie temperature T_C. Meticulous optimization of growth techniques (T_S=230°C, As₂:Ga=5:1 and Ta=250°C) leads to reproducible physical properties and ferromagnetic transition temperatures well above 148 K.