SiGe semiconductor devices for cryogenic power electronics - IV

We are developing power semiconductor devices based on SiGe, for operation at deep cryogenic temperatures. Cryogenic power devices and circuits are of interest for space missions to extremely cold environments. There are also potential applications on Earth in commercial, industrial, and defense systems that incorporate cryogenics or superconductivity. We report results for heterojunction bipolar transistors (HBTs). These are NPN-type with the usual arrangement of a SiGe base region, to provide high gain over a wide temperature range. However, our designs differ from those of the usual HBT in that ours are designed for higher current and voltage and for cryogenic operation, and we are not concerned with ultra-high frequency capability. We have achieved 5 A and 50 V, and current gains up to -100 at room temperature which increase an order of magnitude upon cooling, as expected. Also, we have built basic 100-W boost power-converter circuits using only SiGe active devices (diode and HBT), which operate over an ambient temperature range from room temperature down to the minimum tested temperature of -30 K.