Epitaxial Growth of Dilute Magnetic Semiconductors: GaMnN and GaMnP
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Epitaxial Growth of Dilute Magnetic Semiconductors: GaMnN and GaMnP Mark E. Overberg, Cammy R. Abernathy, Stephen J. Pearton, Fred Sharifi 1, Arthur F. Hebard 1, Nineta Theodoropoulou 1, Stephan von Molnar 2, Madjid Anane 2, and Peng Xiong 2 Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611, U.S.A. 1 Department of Physics, University of Florida, Gainesville, FL 32611, U.S.A. 2 Department of Physics and MARTECH, Florida State University, Tallahassee, FL 32306, U.S.A.
ABSTRACT Epitaxial growth of the dilute magnetic semiconductors GaMnP and GaMnN has been investigated by Gas Source Molecular Beam Epitaxy (GSMBE). GaMnP films grown with < 4.5% Mn show the preferential formation of the second phases MnP and Mn5.64P3, resulting in only a slight deviation from purely diamagnetic behavior. GaMnN films grown on both Al2O3 and Metal-Organic Chemical Vapor Deposition (MOCVD) derived GaN surfaces show strong ferromagnetism when grown with either C codoping or at elevated temperatures to raise the concentration of n-type carriers. Comparable GaMnN films grown under conditions which produce highly resistive material show only paramagnetism, indicating the importance of carrier concentration on the resulting magnetic behavior. The formation of second phases was not observed in the GaMnN material for Mn concentrations less than 9%.
INTRODUCTION Since the invention of the transistor, all facets of semiconductor electronics technology have been based upon the exploitation of the electron charge. Currently, a large research effort is centered upon methods to also exploit the property of electron spin. For many years it has been hypothesized that “spintronic” devices that utilize the quantum properties of the electron spin wavefunction will allow great advances in the development of electro-optic switches, ultrasensitive magnetic field sensors, and particularly, quantum-based logic and memory for high speed computation(1-3). However, its has been found that directly mating electronic materials (semiconductors) with spin materials (ferromagnetic metals) leads to interfacial problems due to the dissimilar nature of the materials’ crystal structure, bonding, physical, and chemical properties(4). Another solution is the dilute magnetic semiconductor (DMS), which consists of a semiconductor host heavily doped with a magnetic ion. A DMS material could permit direct integration with current semiconductor devices. Several theories have been presented on the nature of DMS-related ferromagnetism(5,6). In the theory based upon a bound magnetic polaron (BMP) model, predicted Curie temperature (TC) values are presented for 5% Mn in various III-V and II-VI semiconductors with a concentration of free holes equal to 3.5x1020/cm3 (6). To date, the best experimental TC values for InMnAs, GaMnSb, and GaMnAs reasonably agree with theory, but are still well below room temperature(7-9). The III-V DMS material GaMnN is predicted to have a TC well above room temperature, while the material GaMnP is expected to be
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