ACKNOWLEDGMENTS I gratefully express my appreciation to the members of my supervisory committee for their support and cooperation. In particular, I thank Dr. S. S. Li for his guidance, enthusiasm and professional example-, and Dr. F. A. Lindholm for his continuing interest in the research. A special expression of appreciation is due Dr. A. D. Sutherland for his advice and support during the first year of my graduate work. I am also indebted to D. Yuen for his help with measurements on the gallium- and'indium-doped samples, to M. Riley for the fabrication and measurement of the boron samples, and to W. Axson and R. Wilfinger for their invaluable help with various laboratory procedures. This investigation was made possible by the Air Force Institute of Technology. The research was jointly supported by the National Bureau of Standards Contract No. 7-35741 and the National Science Foundation Grant No. ENG 76-81828.