Negative differential resistance in metal (CoSi/sub 2/)/insulator (CaF/sub 2/) resonant tunneling diode

The authors report on the first observation of negative differential resistance (NDR) in a nanometer-thick metal insulator resonant tunneling diode. As materials for the single-crystalline metal/insulator, they chose CoSi/sub 2/ and CaF/sub 2/ because they have the fluorite lattice structure and are lattice-matched to Si relatively well. In contrast to semiconductor or semiconductor/metal heterostructures, a triple barrier structure is necessary for the NDR because the bottom of the conduction band in bulk CoSi/sub 2/ is far below the Fermi level ( approximately 13 eV) and is difficult to exceed the resonant level in conventional double-barrier structures. It is believed that the observed NDR is due to the electron resonant tunneling transport in nanometer-thick metal/insulator heterostructures.