Growth and Characterization of Diluted Magnetic III-V Compound Semiconductors

点击翻译按钮获取中文摘要

Molecular beam epitaxial (MBE) growth and electric and magnetic properties of diluted magnetic III-V semiconductors, especially (In, Mn) As, are studied. Following is a summary of the research results. Molecular Beam Epitaxial Growth : Maximum Mn concentration that can be incorporated into InAs lattice without having second phase (which is MnAs) is critically dependent on the growth temperature during MBE growth. At 300ﾟC, x (in In_<1-x>Mn_xAs) has to be<0.03 and the conduction is p-type whereas at 200ﾟC, x<0.25 and n-type.Characterization of Epitaxial layers : (1) Magnetism All n-type samples are paramagnetic and the direct interaction between Mn ions is antiferromagnetic with nearest neighbor J of -1.6 K. All p-type samples are paramagnetic at medium to high temperatures, but show spontaneous magnetization at low temperatures. Paramagnetic component which saturates only at high magnetic fields (4 to 9 T) is also present. The spontaneous magnetization makes up for 25 % of saturation m … More agnetization at the lowest temperature (1.4K) investigated. (2) Electrical Properties n-type samples show negative magnetoresistance at low temperatures. No hysteresis is observed. The Hall resistance of p-type samples is dominated by anomalous Hall effect. At temperatures below 7.5 K, hysteresis appears in B dependence of Hall resistance together with negative magnetoresistance extending to high magnetic fields. Hysteresis is only observed in p-type samples. This can be explained by the presence of large magnetic polarons with canted spins inside. The origin of the canting is believed to be the exchange interaction between holes and Mn ions. The interaction is mostly ferromagnetic with spin texture (i. e. canting) due to spin-orbit interaction of to Mn-Mn antiferromagnetic interaction. Rotation of polarons gives rise to the spontaneous magnetization, whereas the alignment of spins with high magnetic fields results in paramagnetic response at high fields. This is the first observation of weak ferromagnetism due to localized carrier-spin exchange in diluted magnetic semiconductors. Less