Fe/（Ga,Mn）As heterostructures were fabricated by all molecular-beam epitaxy.Double-crystal X-ray diffraction and high-resolution cross-sectional transmission electron micrographs show that the Fe layer has a well ordered crystal orientation and an abrupt interface.The different magnetic behavior between the Fe layer and（Ga, Mn）As layer is observed by superconducting quantum interference device magnetometry.X-ray photoelectron spectroscopy measurements indicate no Fe_2As and Fe-Ga-As compounds,i.e.,no dead magnetic layer at the interface, which strongly affects the magnetic proximity and the polarization of the Mn ion in a thin（Ga,Mn）As region near the interface of the Fe/（Ga,Mn）As heterostructure.
We report that,by linearly polarized pumping of different wavelengths,Kerr transients appear at zero magnetic field only in the case when GaMnAs samples are initialized at 3 K by first applying a 0.8 Tesla field and then returning to zero field.We find that,instead of magnetization precession,the near-band gap excitation induces a coherent out-of-plane turning of magnetization,which shows very long relaxation dynamics with no precession.When photon energy increases,the peak value of the Kerr transient increases,but it decays rapidly to the original slow transient seen under the near-band-gap excitation.
LUO Jing,ZHENG HouZhi,SHEN Chao,ZHANG Hao,ZHU Ke,ZHU Hui,LIU Jian,LI GuiRong,JI Yang & ZHAO JianHua State Key Laboratory for Superlattices and Microstructures,Institute of Semiconductors,Chinese Academy of Sciences,Beijing 100083,China
A spin-injection/-detection device has been fabricated based on the multiple quantum well light emitting diode (LED) structure. It is found that only a broad electroluminescence (EL) peak of a full width at half maximum of 8.6 nm appears at the wavelength of 801 nm in EL spectra with a circular luminescence polarization degree of 18%, despite PL spectra always show three well resolved peaks. The kinetic energy gained by injected electrons and holes in their drift along opposite directions broadens the EL peak, and makes three EL peaks converge together. The same process also destroys the injected spin polarization of electrons mainly dominated by the Bir-Aronov-Pikus spin relaxing mechanism.
In this review article,we review the progress made in the past several years mainly regarding the efforts devoted to increasing the Curie temperature(T C) of(Ga,Mn)As,which is most widely considered as the prototype ferromagnetic semiconductor.Heavy Mn doping,nanostructure engineering and post-growth annealing which increase T C are described in detail.
