GaAs宽量子阱中二维空穴系统

场效应管、异质结激光器等半导体量子器件的工作特性与组成这些器件的二维载流子系统的物理性质有密切的联系。分子束外延生长技术制备的超高迁移率二维电子/空穴系统被广泛应用于研究量子霍尔效应、弹道输运和Berry相位等物理现象。相比于二维电子，二维空穴系统中能量相近的p-轨道亚能带之间通过自旋-轨道作用相互耦合，从而使得二维空穴具有各向异性，非抛物线的复杂的E-k色散曲线。电场、应力、磁场等也会极大的影响色散曲线。迄今为止宽量子阱中二维空穴系统的能级结构及其输运特性仍然没有被系统性地研究。在本课题中，我们将对宽量子阱中二维空穴系统的磁输运特性进行系统性地测量。我们将会研究：1. 强磁场中不同朗道能级之间的交错及其随空穴浓度、量子阱宽和量子阱对称性之间的关系；2.朗道能级交错点附近量子霍尔效应的相变。这项研究将为日后进一步深入研究宽量子阱二维空穴系统提供实验指导。

The physics of two-dimensional electron/hole systems plays an important role in modern semiconductor quantum devices such as high electron mobility transistors, heterostructure lasers, etc., which are assembled by connecting individual 2D systems with tunneling/diffusion junctions. The state-of-the-art ultra-high mobility 2D electron/hole systems grown by molecular beam epitaxy have achieved > 10^6 cm^2/(Vs) mobility and >10 um mean-free-path at low temperatures. A lot of quantum phenomena have been discovered and studied in these systems, such as quantum Hall effect, ballistic transport, Berry phase, etc. Compared to 2D electron system, the 2D hole system, especially when confined in wide quantum wells, is still poorly understood. The p-orbital states are strongly coupled with each other through the spin-orbital coupling, leading to complicate, anisotropic, non-parabolic subband dispersion which are sensitive to external perturbations such as electric field, strain, magnetic field, etc. In this study we propose to perform the first systematic magneto-transport study of ultra-high mobility two-dimensional hole system confined in wide GaAs quantum wells at low temperature and high magnetic field. We will study: 1. The Landau level crossings and their dependence on the hole density, quantum well width and symmetry; 2. Evolution and phase transitions of quantum Hall effects at Landau level crossings. Through this study, we expect to create an experimental chart to pilot future in-depth studies.