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(A_(sGa))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 MnI out of the GaMnAs lattices so as to raise the Curie temperature TC.Meticulous optimization of growth techniques(T_(S)=230℃,A_(s2):Ga=5:1 and Ta=250℃)leads to reproducible physical properties and ferromagnetic transition temperatures well above 148 K.