We propose to develop power semiconductor devices (diodes and transistors) for power-management and actuator-control circuits operating at cryogenic temperatures. Cryogenic power electronics can provide important benefits both for space and commercial applications: higher efficiency, reduced size, weight and complexity, and improved system reliability. Of primary importance to spacecraft is reduction or elimination of thermal control and its attendant power usage, weight, size and added electronics. We propose using the silicon-germanium (SiGe) materials system because of its powerful design flexibility, compatibility with silicon processing, and ability to combine desirable features of both silicon and germanium. Conventional Si-based electronics has not proved adequate for deep-cryogenic temperature (down to 30 K) power applications, whereas SiGe operates well down to these cryogenic temperatures. The objective of Phase I is to demonstrate the advantages of SiGe for metal-insulator-semiconductor (MIS) structures and heterojunction bipolar transistors (HBT), which are essential elements of advanced power devices to be developed in follow-on work. The proposed SiGe cryogenic power devices are an innovation because there are presently no power semiconductor devices based on SiGe and designed for cryo-genic applications. POTENTIAL COMMERCIAL APPLICATIONS Potential application areas in the industrial, commercial and defense sectors include magnetic resonance imaging, energy storage (inductive or capacitive), cryogenic or superconducting power transmission and distribution, cryogenic or superconducting motors and generators, magnetic confinement, particle accelerators, aerospace vehicles, and radio-frequency power amplifiers. These applications can benefit from improved efficiency of cryogenic power electronics and reduced size and weight. Many of these are natural application areas because they already incorporate a cryogenic environment. Also, cryogenic tempera-tures around 30 K have received additional emphasis by the recent discovery of superconductivity in MgB2, which promises to be a practical material for both electronic and large-scale applications.
