9804313 Heiman The aim of this research is to investigate the synthesis of semiconductors that are ferromagnetic the overall goal is to discover new device materials useful in the information age. The project addresses the synthesis and properties of high-Curie- temperature, ferromagnetic GaAs doped with Mn, which has the potential to exhibit strong magnetic as well as electrical and optical behavior. Magnetic semiconductors such as the europium chalcogenides are good magnets but have poor electrical properties and limited optical properties, while dilute magnetic semiconductors such as manganese-doped II-VI materials show better electrical and optical properties but weak magnetism. Thin films and quantum wells of Gal-xMnxAs/Ga1-yAlyAs will be grown by MBE. It is known that Mn2+ substituting for Ga3+ in GaAs leads to deep acceptor states. When the hole concentration is above the Mott criterion (~2x1019 cm-2) a metallic state is produced. It is believed that a strong p-d exchange between the magnetic Mn2+ ions and holes generates ferromagnetism. A key issue is how to control the number of holes in the material. The hole concentration, and ultimately the Curie temperature, depend on the degree of compensation of the holes by unknown donor-like states. Proper control of the manganese and hole concentration is expected to lead to increased Curie temperatures. Further investigations will address the self-assembly of MnAs quantum dots, and the feasibility of building multilayer structures for giant magnetoresistance materials. %%% The project addresses basic research issues in a topical area of materials science having high technological relevance. The research will contribute basic materials science knowledge at a fundamental level to important aspects of electronic/photonic/magnetic devices. The basic knowledge and understanding gained from the research is expected to contribute to improving the performance of advanced devices by providing a fundamental understan ding and a basis for designing and producing improved materials, and materials combinations. An important feature of the program is the integration of research and education through the training of students in a fundamentally and technologically significant area.
