Three-terminal superconducting devices

The transistor has a number of properties that make it so useful. We discuss these and the additional properties a transistor would need to have for high performance applications at temperatures where superconductivity could contribute advantages to system-level performance. These properties then serve as criteria by which to evaluate three-terminal devices that have been proposed for applications at superconducting temperatures. FETs can retain their transistor properties at low temperatures, but their power consumption is too large for high-speed, high-density cryogenic applications. We discuss in detail why demonstrated superconducting devices with three terminals - Josephson effect based devices, injection controlled weak links, and stacked tunnel junction devices such as the superconducting transistor proposed by K. Gray and the quiteron - each fail to have true transistor-like properties. We conclude that the potentially very rewarding search for a transistor compatible with superconductivity in high performance applications must be in new directions.