Electrically-Generated Spin Polarization in Non-Magnetic Semiconductors
Technical Report,01 Jul 2012,31 Dec 2015
University of Michigan Ann Arbor
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The objective of the research was to investigate and determine the mechanism that produced electrically-generated electron spin polarization in non-magnetic semiconductor heterostructures. Electrically-generated electron spin polarization was shown to be inversely proportional to the measured momentum-dependent spin splitting in strained indium gallium arsenide, contrary to theoretical expectation. The measurements were conducted by systematically varying the direction and magnitude of the in-plane current and net drift momentum in a device with a cross-bargeometry. The role of electrically-generated electron spin polarization in producing dynamic nuclear polarization was investigated, and nuclear spin polarization was produced that could be aligned either with or against the applied magnetic field, depending on the direction of the current. Aseries of indium gallium arsenide epilayer samples with varying indium composition and doping density were produced and measured in order to determine how changing the sample parameters, such as spin-orbit splitting, spin relaxation time, momentum scattering time, and carrier density,affect the electrical spin generation efficiency.