A high-temperature superconductor latching driver operated at 30 K for a single-flux-quantum/semiconductor interface
Tsunehiro Hato, Masahiro Horibe, Naoki Harada +5 more
We report on a latching-type driver operated at 30 K for the output interface of single-flux-quantum (SFQ) circuits. Ramp-edge-type high-temperature superconductor (HTS) junctions showed only small inherent hysteresis in current–voltage characteristics at a temperature of 30 K. To have hysteresis large enough for latching operation, we chose La-doped YbBaCuO as a counter electrode of an interface modified junction, and used amorphous LaSrAlTaO to form an additional barrier to the interface modified barrier. The junction shunted with optimized capacitance showed sufficiently large hysteresis of 33%, which is as large as that of a non-shunted junction at 4.2 K. We employed 20 kA cm−2 as the critical current density (Jc) of the junction to fabricate dc/SFQ, Josephson transmission lines (JTLs) and the latching driver on the same chip. It is smaller than the optimum current density that gives the smallest punchthrough probability of the junction, which was calculated to be 10−12 for a 30 Gbps ac bias by using the junction parameters at 30 K. However, the probability for Jc of 20 kA cm−2 is still smaller than that of low-temperature semiconductor junctions because of the larger Jc of the HTS junctions. The fabricated latching driver successfully converted the SFQ pulse, which passed through several JTLs from the dc/SFQ circuit, to a 1 mV level signal at 30 K.
Superconductor Science and Technology•Nov 7, 2003•3 citations