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Time-Resolved Studies of Magnetic and Non-Magnetic Narrow-Gap Semiconductors
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In recent years, spin relaxation, injection, and manipulation in semiconductors have attracted considerable interest because of several potential applications in "spintronic" devices and the necessity to understand and control spin-based phenomena. In light of the growing interest in spin-related phenomena and devices, there is now renewed interest in the science and engineering of narrow gap semiconductors (NGS). NGS based heterostructures are particularly interesting for spintronic applications due to their large spin-orbit coupling, which leads to considerable zero-field spin splitting. NGS are also candidates for electronic applications, such as high-speed and low-power microprocessors; as reported recently by Intel. Furthermore, as switching rates in electronic devices are pushed to even higher frequencies, it is important to understand dynamics in semiconductors such as NGS on femtosecond time-scales. In this thesis, time-resolved studies of magnetic and non-magnetic NGS using ultrafast-laser spectroscopy techniques such as pump-probe spectroscopy and magneto-optical Kerr/Faraday effect, are reported. Our samples include: InSb-based quantum wells with different confinement potentials; InMnSb films, the newest III-V ferromagnetic semiconductors; and InAs films. The samples for these studies have been provided by the groups of Prof. Santos at the University of Oklahoma, Prof. Furdyna at the University of Notre Dame, and Prof. Guido at Virginia Tech. The objectives in this thesis have been to: a) understand charge/spin dynamics in NGS with novel confinement potentials, b) probe the effect of magnetic impurities on the spin/charge dynamics, and c) develop concepts for spin based device applications. Several specific questions and concepts have been addressed including: the effect of large spin-orbit interaction in NGS on the dynamics, how large Rashba spin splitting in these materials affect the spin coherence life time, and carrier/spin dynamics in ferromagnetic semiconductor structures.
- Doctoral Dissertations