Two-dimensional Electrons in Modulation-Doped AlAs Quantum Wells

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This experimental condensed matter physics project focuses on electron interaction physics in high-quality, quantum-confined semiconductor structures. The program includes studies of both fabrication, via molecular beam epitaxy technique, and of electronic transport properties at low temperatures and high magnetic fields where electron correlation phenomena dominate. The emphasis is on high-quality two-dimensional (2D) electron systems confined to selectively-doped AlAs quantum wells. The 2D electrons in AlAs have parameters that are very different from those of the standard 2D electrons in GaAs: they have a much larger and anisotropic effective mass, a much larger effective g-factor, and they occupy multiple conduction band valleys. Since these parameters influence the electron-electron interaction, AlAs 2D electrons thus provide a crucial and important test-bed for new many-body physics. The proposed projects are performed primarily by students, both graduate and undergraduate, and form a crucial part of their education and training. Quality education, in cutting edge technology and physics, is therefore integrated into the research.This research involves an experimental study of interaction between electrons in specially designed semiconductor structures. In these structures, the electrons are confined to specific layers in the material and are spatially separated from the dopant atoms (impurities). As a result, the electron system iis very pure and the physics is dominated by electron-electron interaction rather than electron-dirt (-iimpurity) interaction. Such systems serve as a testing ground for some of the most exciting physics involving interaction. The particular system that is explored in this work involves the confinement of electrons in an AlAs (aluminum arsenide) layer. The electrons in AlAs have parameters that are very different from the more conventional system of electrons in a GaAs (galium arsenide) layer so that new phenomena is expected to occur. This research program includes studies of both fabrication, via molecular beam epitaxy technique, and of electronic transport properties at low temperatures and high magnetic fields where electron interaction phenomena dominate. The major part of the research will be performed by graduate and undergraduate students. The students will do state-of-the-art research, under close supervision, on some of the most exciting and challenging problems in solid state physics. Both the fabrication and the physics of advanced layered semiconductor structures are at the forefront of today's science and technology. Therefore, while the subject of the proposed research is fundamental, well-trained and educated students in this field will be invaluable resources for the US as well as the rest of the world.