Josephson flux-flow resonances and transistors based on YBa/sub 2/Cu/sub 3/O/sub 7/ step edge junctions

The flexibility of step edge junctions is very attractive for device applications. With an improved process based on an amorphous carbon mask technique and electron beam lithography, we were able to fabricate high quality YBa₂Cu₃0₇ long Josephson junctions across sharp and straight step edges on (001) LaAl0₃ substrates. Flux-flow resonances were observed in the current-voltage curves for some long Josephson junctions. The resonance voltage can linearly be tuned by an applied magnetic field. Asymmetric in-line type Josephson flux-flow transistors were fabricated based on the long Josephson junctions. The critical current I_c, and the response voltage V at a fixed bias current I_b, were measured as a function of the control current I through a control line inductively coupled to the junction. A maximum current gain of g=17, and a corresponding transresistance of r_m=9 Ω, were achieved at 4.2 K.