First-principles design of quantum superstructures for development of spin-electronics

在半导体中注入自旋极化载流子是实现电子自旋器件的基本技术，该器件既利用电子电荷，又利用自旋自由度。为了提高自旋注入半导体的效率，利用第一性原理电子结构计算理论设计了完全自旋极化（半金属）铁磁体及其具有半导体的量子超结构，这些超结构有望成为自旋注入源的候选者。结果表明：(1)从理论上设计了新型半金属铁磁体，即锌-闪锌矿CrAs、CrSb和CrP。(2)这些材料的自旋极化几乎不受自旋轨道相互作用的影响。(3) as位上的反位缺陷，即Cr杂质，降低了混合锌CrAs的自旋极化。(4)锌-闪锌矿CrAs/GaAs（001）多层结构保持了半金属性质。(5)提出了一种非均匀掺杂的方法来实现硅基铁磁半导体。

Injection of spin-polarized carriers into semiconductors is a basic technology for manifestation of spin-electronic devices which exploit both electronic charge and spin degrees of freedom. In order to improve the efficiency of spin-injection into semiconductors, completely spin-polarized (half-metallic) ferromagnets and their quantum superstructures with semiconductors, which are expected to be promising candidates for the source of spin-injection, have been designed theoretically by using first-principles electronic structure calculations. The results obtained by this project are as follows:(1) New half-metallic ferromagnets, zinc-blende CrAs, CrSb, and CrP, are designed theoretically.(2) The spin-polarization in these materials in almost unaffected by the spin-orbit interaction.(3) Antisite defects, Cr impurities at As-sites, reduce the spin-polarization in zinc-blende CrAs.(4) Zinc-blende CrAs/GaAs (001) multilayer structures maintain the half-metallic behavior.(5) An inhomogeneous doping method in suggested to realize Si-based ferromagnetic semiconductors.