Liu Xingchen, Tang Ning, Fang Chi, Wan Caihua, Zhang Shixiong, Zhang Xiaoyue, Guan Hongming, Zhang Yunfan, Qian Xuan, Ji Yang, Ge Weikun, Han Xiufeng, Shen Bo
State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University Beijing 100871 China
Frontiers Science Center for Nano-optoelectronics & Collaboration Innovation Center of Quantum Matter, Peking University Beijing 100871 China.
RSC Adv. 2020 Mar 27;10(21):12547-12553. doi: 10.1039/d0ra00464b. eCollection 2020 Mar 24.
Spin relaxation, affected by interfacial effects, is a critical process for electrical spin injection and transport in semiconductor-based spintronics. In this work, the electrical spin injection into n-GaN n-GaN/MgO/Co tunnel barrier was realized, and the interface-related spin relaxation was investigated by both electrical Hanle effect measurement and time-resolved Kerr rotation (TRKR) spectrum. It was found that the spin relaxation caused by interfacial random magnetostatic field was nearly equal to the intrinsic contributions at low temperature (less than 80 K) and could be suppressed by smoother n-GaN/Co interface. When the interfacial random magnetostatic field was suppressed, the spin relaxation time extracted from the electrical injection process was still shorter than that in bulk conduction band, which was attributed to Rashba spin-orbit coupling (SOC) induced by the interface band bending in the depletion region. Due to thermal activation, luckily, the spin relaxation induced by the interfacial Rashba SOC was suppressed at temperatures higher than 50 K. These results illustrate that (1) spin relaxation time could be as long as 300 ps for GaN and (2) the influences of interfacial effects could be engineered to further prolong spin relaxation time, both of which shed lights on GaN-based spintronic devices with direct and wide bandgap.
受界面效应影响的自旋弛豫是基于半导体的自旋电子学中电自旋注入和输运的关键过程。在这项工作中，实现了向n-GaN/n-GaN/MgO/Co隧道势垒的电自旋注入，并通过电Hanle效应测量和时间分辨克尔旋转（TRKR）光谱研究了与界面相关的自旋弛豫。研究发现，由界面随机静磁场引起的自旋弛豫在低温（低于80K）下几乎等于本征贡献，并且可以通过更平滑的n-GaN/Co界面来抑制。当界面随机静磁场被抑制时，从电注入过程中提取的自旋弛豫时间仍然比体导带中的自旋弛豫时间短，这归因于耗尽区界面能带弯曲引起的Rashba自旋轨道耦合（SOC）。幸运的是，由于热激活，在高于50K的温度下，界面Rashba SOC引起的自旋弛豫被抑制。这些结果表明：（1）GaN的自旋弛豫时间可以长达300ps；（2）可以通过设计界面效应来进一步延长自旋弛豫时间，这两点都为具有直接和宽带隙的GaN基自旋电子器件提供了启示。
