GeTe基稀磁半导体的载流子调制及磁性机理研究

The investigation of both carrier modulation and magnetism in diluted magnetic semiconductors (DMSs) is of great significance in spintronics applications. The GeTe-based DMSs have vast potential in phase-change memory, magnetic field sensors, and spin logic devices. Among these semiconductors, GeFeTe thin film has attracted considerable attention due to its high Curie temperature and interaction between electronic transport and magnetic behavior. A large hole density is always observed in GeTe-based DMS thin films. In order to explore the origin of magnetism in GeTe-based DMS and utilize it in device application, it is necessary to obtain films with controllable carrier type and concentration. Thus, in this project, we aim at modulating the carrier in GeTe-based DMS via co-doping with Bi and Fe. To build the physical model of the magnetism in IV-VI DMS, a series of (Ge, Fe, Bi)Te high-quality epitaxial films with various carrier types and concentrations will be deposited using pulsed laser deposition. The dependence of magnetic properties on carrier type and density, Ge vacancy, as well as Fe distribution in (Ge, Fe, Bi)Te films will be determined. Based on the built physical model, the magnetic properties can be controlled in DMS (Ge, Fe, Bi)Te films by the variation of the physical parameters mentioned above.

稀磁半导体电磁性质的调控及其磁性机制的研究是自旋电子学研究的重要方面。GeTe基稀磁半导体在相变存储器，磁传感器及自旋逻辑器件中有着广阔的应用前景，其中GeFeTe薄膜更是因为相对高的居里温度以及电输运和磁化行为间的关联作用而受到学者的广泛关注。由于GeTe基稀磁半导体具有很高的空穴浓度，为了研究其磁性机理并实现在实际自旋器件中的应用，载流子类型及浓度的调控是极为必要的。因此，在本项目中，我们旨在通过Bi与Fe元素共掺杂的方式，实现GeTe基稀磁半导体(Ge, Fe, Bi)Te的载流子调制。利用脉冲激光沉积技术生长一系列具有不同载流子类型及浓度的高质量外延薄膜，分析(Ge, Fe, Bi)Te磁学性质对载流子类型及浓度的依赖关系，综合Ge空位及Fe元素的含量及分布对薄膜的磁学性质的影响，建立GeTe基稀磁半导体的磁性机理模型，并进一步实现稀磁半导体(Ge, Fe, Bi)Te的磁性调控。

本项目以稀磁半导体磁性调控为研究背景，运用成分改变、组分控制、热处理等手段，对稀磁半导体GeFeTe外延薄膜的磁学性质的调控进行了较为系统的研究。主要研究内容和成果包括通过对稀磁半导体GeFeTe外延薄膜中Fe含量的改变，实现了对稀磁半导体GeFeTe的磁学性质的调控。通过热处理的外部激励的手段，实现了对晶态稀磁半导体GeFeTe外延薄膜磁学性质的调控，对于高Fe含量的稀磁半导体GeFeTe外延薄膜，通过热处理实现了其从反铁磁到铁磁的转变。研究发现，通过对晶态稀磁半导体GeFeTe外延薄膜进行后退火热处理，可以改变薄膜内部Fe元素的分布，进而改变Fe原子的局域环境，进而影响其磁学性质。通过对稀磁半导体GeFeTe外延薄膜的磁学性质对Fe元素含量、分布及局域环境的依赖关系的研究，建立了稀磁半导体GeFeTe的磁性机制的模型。