Science and Engineering

Purdue University

Michael Manfra
West Lafayette, IN
December 2012

In very low disorder condensed matter systems, new correlated behavior often emerges that cannot be understood through consideration of the properties of the individual constituent particles. Among such systems, the two-dimensional electron gas (2DEG) confined in a GaAs quantum well holds a special position. Historically every time the quality of the 2DEG, as measured by electron mobility, has increased by a factor of two, new correlated electron phases have been observed that reshape our understanding of how electrons behave collectively. However, mobility in GaAs 2DEGs peaked a decade ago, limited by the background impurity concentration in the GaAs epilayer. Further improvement is hindered by the purity of the commercially available gallium metal (~100 parts per billion impurities) used in molecular beam epitaxy growth. This project strives to produce a 2DEG in a GaAs quantum well with an order of magnitude improvement in low temperature electron mobility over the current best. Through novel use of metal purification technology, innovative methods in molecular beam epitaxy and advanced electrical characterization, this project will produce 2DEGs in which impurity atoms in GaAs are controlled to 1 part in 1012, creating a new frontier for the study of strongly interacting electronic phases of matter.

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