Growth Dynamics and Properties of Compound Semiconductor Layers Prepared by Low Temperature Molecular Beam Epitaxy

为了将自旋极化电流注入到半导体中，我们采用MBE再生技术制备了铁磁/非磁性半导体异质结构，并研究了它们的电流-电压特性和电致发光极化。研究结果总结如下：在分子束外延制备的铁磁性半导体（Ga, Mn） as /非磁性半导体（in, Ga） as pn结发光二极管中成功实现了非磁性半导体的电自旋注入。我们观察到了铁磁/非磁pn结电致发光光谱中的滞后极化现象。剩余电致发光极化程度约为±1%，其温度依赖性几乎与（Ga, Mn） As磁化强度成正比。我们制备了铁磁性（Ga, Mn） As/非磁性（In, Ga） As半导体发光二极管，它们生长在晶格松弛的n-In_xGa_<1-x>As（…More x=0.15-0.18）缓冲层上，使（Ga, Mn） As的磁易轴垂直于平面。我们测量了从衬底背面发射的光的偏振程度，并观察了滞后极化。为了明确（Ga, Mn） As/GaAs异质界面的价带排列，我们在（Ga, Mu） As中制备了不同Mn浓度的（Ga, Mn） As/i-GaAs/p-GaAs p-i-p结构，并测量了它们的电流-电压特性对温度的依赖关系。发现这种p-i-p结构的电流-电压特性取决于偏置电压的极性，这表明当空穴电流从（Ga, Mn） As注入GaAs时，在界面处存在势垒。假设电流主要由肖特基势垒上的热辐射主导，我们分析了结果，发现由（Ga, Mn） As的费米能测得的势垒高度约为100 meV，与（Ga, Mn） As中的Mn浓度无关。少

In order to inject spin-polarized electrical current into semiconductors, we fabricated ferromagnetic/nonmagnetic semiconductor heterostructures by employing MBE regrowth technique, and investigated their current-voltage characteristics and electroluminescence polarization. The summary of the research results is as follows :Electrical spin injection into nonmagnetic semiconductor is successfully achieved in ferromagnetic semiconductor (Ga, Mn) As/nonmagnetic semiconductor (In, Ga) As pn junction light emitting diodes prepared by molecular beam epitaxy. We observed hysteretic polarization in electroluminescence spectra of ferromagnetic/nonmagnetic pn junction. The degree of the remanent electroluminescence polarization was about ±1%, of which the temperature dependence is almost proportional to that of the magnetization of (Ga, Mn) As.We fabricated ferromagnetic (Ga, Mn) As/nonmagnetic (In, Ga) As semiconductor light emitting diodes, which are grown on lattice-relaxed n-In_xGa_<1-x>As ( … More x=0.15-0.18) buffer layer so that the magnetic easy axis of (Ga, Mn) As directs perpendicular to the plane. We measured the degree of the polarization of light emitted from the backside of the substrate, and observed hysteretic polarization.In order to clarify the valence band alignment at (Ga, Mn) As/GaAs heterointerface, we fabricated (Ga, Mn) As/i-GaAs/p-GaAs p-i-p structures with different Mn concentration in (Ga, Mu) As, and measured the temperature dependence of current-voltage characteristics of them. It is found that the current-voltage characteristics of such p-i-p structures depend on the polarity of bias voltage, which suggest the existence of a potential barrier at the interface when hole current is injected from (Ga, Mn) As into GaAs. Assuming that the current is dominated by thermal emission over a Schottky barrier, we analyzed the results and found that the barrier height measured from the Fermi energy of (Ga, Mn) As is about 100 meV, which does not depend on the Mn concentration in (Ga, Mn) As. Less