****Technical Abstract**** This project consists of two research thrusts on the magnetic and spin-dependent electronic properties of tailored semiconductor nanostructures. The first utilizes the persistent photoconductivity (PPC) in AlGaAs for a detailed examination of the electronic spin transport/relaxation as a function of its carrier concentration. PPC permits in situ photodoping of the semiconductor channel, thus enabling measurements of spin accumulation and lifetime over broad carrier concentration ranges in one and the same sample. The research is expected to produce comprehensive and detailed knowledge of the spin lifetime as well as various carrier scattering processes relevant to spin relaxation. The second line of research employs high-sensitivity semiconductor Hall magnetometry techniques to study the static and dynamic magnetic properties of transition metal-doped InAs quantum dots (QDs) grown by MBE. The goal of the proposed research is to measure the magnetization of a small array of, even an individual, QDs via an integrated micro/nano Hall magnetometer. The scheme may facilitate a direct correlation of the measured magnetic properties of the QDs with their structural/chemical characteristics, potentially enabling a definitive understanding of the origin of the ferromagnetism in the nano-structured diluted magnetic semiconductors. This grant supports directly the research and education of a PhD student and indirectly other students already involved with this project.
Spintronics is an emerging technology which utilizes the electronic spin to provide new and improved electronic device functionality. For more than two decades spintronics in metallic devices has enjoyed great scientific, technological and commercial successes. However, the utilities have been limited to passive devices such as sensors and memory elements. The research into semiconductor spintronics is motivated by the need to produce true three-terminal spintronic logic devices for potential transformative applications such as nonvolatile reprogrammable logic, spin-based opto-electronics, and quantum computation. The research here addresses two key challenges in semiconductor spintronics: coherent manipulation, transport and detection of electron spins in a semiconducting medium and the understanding of the ferromagnetism in transitional metal-doped semiconductors. The first project utilizes light (photo-excitation) to tune the carrier density of an AlGaAs semiconductor channel, enabling a detailed examination of the electronic spin transport/relaxation over a broad carrier concentration range in one and the same sample. The latter employs a high-sensitivity integrated micro/nano Hall magnetometer to study the static and dynamic magnetic properties of a small array of, even an individual, transition metal-doped InAs quantum dots. This grant supports directly the research and education of a PhD students and indirectly other students already involved in this project. It affords them the opportunity to interact closely with the students and researchers at the Institute of Semiconductors, a premiere materials research institution in China.
