Superconducting current injection transistor with very high critical-current-density edge-junctions

A Superconducting Current Injection Transistor (Super-CIT) was fabricated with very high critical current-density edge-junctions. The junctions have a niobium base electrode and a lead-alloy counter electrode. The length of the junctions is 30μm and the critical-current density is 190KA/cm². The Super-CIT has a current gain of 2, a large signal transresistance of 100mV/A and the turn-on delay, inferred from the junction resonance, is 7ps. The power dissipation is 3.5μW and the power-delay product is 24.5aJ. Gap reduction due to heating was observed, limiting the maximum power dissipation per unit length to 1.1 μW/μm. Compared to lead-alloy Super-CITs the device is five times smaller, three times faster and has a three times larger output voltage. The damping resistor and the contact junction could also be eliminated.