We have measured the tunneling conductance of YBa2Cu3O7/Pb planar tunnel junctions fabricated on superconducting (110)-oriented YBa2Cu3O7 thin films exhibiting zero-resistance superconducting transition temperatures (Tc’s) between 88 and 89.5 K. The conductance is the same as we and other groups have measured on (100)- and (103)-oriented YBa2Cu3O7/Pb junctions and quantitatively different from c-axis tunneling. The ab-plane transport is comparable to that measured in (001)-oriented YBa2Cu3O7 thin films, and the transport anisotropy varies between 65 and 80 from 300 K to Tc, respectively. This anisotropy is higher than that previously measured in both (110)-oriented and c-axis aligned (100)-oriented films, but it is comparable to that measured in single crystals.

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We discuss the feasibility of a semiconductor superlattice oscillator which exploits the quenching of propagating dipole domains for the generation of submillimeter waves. We studied the dynamics of electrons in a semiconductor superlattice by performing a simulation based on a drift-diffusion model, taking into account feedback from a resonant circuit. The simulation delivers propagating dipole domains which are quenched before they reach the anode. The periodic formation and quenching of domains creates a self-sustained oscillation of the current through the superlattice. The frequency of the oscillation can be more than three times higher than without feedback. We suggest that with already existing superlattices an oscillator working in the quenched domain mode can be realized up to almost 500 GHz.

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