9301222 Allen Epitaxial semi-metal/semiconductor heterostructures have the potential to add new dimensions to semiconductor electronics by providing buried interconnects or ground planes or enabling control of quantum transport in resonant tunneling structures and hot electron transistors. Using the unique properties of the Rare-earth monarsenide/GaAs system we propose investigating quantum transport through ultra-thin buried semi-metal layers in compound semiconductors in "transistor like" test structures. The P.I. propose to i) determine the role of quantum confinement in semi-metal quantum wells, ii) measure electron transmission, reflection and loss in semi-metal quantum wells and iii) assess the potential of this material system for resonant tunneling and hot electron transistors. ***