Epitaxial growth of a metal(CoSi2)/insulator(CaF2) nanometer‐thick heterostructure and its application to quantum‐effect devices

Abstract

Metal(CoSi2)/insulator(CaF2) nanometer‐thick heterostructures are grown on a Si(111) substrate, and applied to quantum‐effect electron devices. In the epitaxial growth of a CoSi2/CaF2 multilayer, an epitaxial CoSi2 layer on CaF2 was obtained by the two‐step growth technique, i.e., solid phase epitaxy with the epitaxial Si layer grown in the first step and Co deposited in the second step. An epitaxial CaF2 layer was formed on CoSi2/CaF2 at the low substrate temperature of 450 °C with a partially ionized and accelerated CaF2 beam. Co agglomeration in nanometer‐thick CoSi2 layer was avoided by using these techniques. A resonant tunneling transistor with double CoSi2 quantum wells was fabricated, and a transistor action with the negative differential resistance was observed at 77 K. The transfer efficiency of electrons from the emitter to the collector through the resonant energy levels is estimated to be close to unity. A resonant hot electron transistor structure was also fabricated, and multiple negative d...