Deep Space Cryogenic Power Electronics

Technology Application, Inc. (TAI) is proposing to demonstrate feasibility of implementing silicon germanium (SiGe) strained-gate technology in the power complementary metal oxide semiconductor field effect transistor (CMOSFET) and logic devices for a logic and power transistor controller for space-approved stepper motors at cryogenic temperature. Power electronic systems contain digital and analog circuits, and the increasing complexity of these systems required for deep space missions and naval electric-powered propulsion requires a new approach in material and processes to operate efficiently at cryogenic temperature. The metal oxide semiconductor field effect transistor (MOSFET) is the building block for both digital and analog circuits. Silicon (Si) is a good material for fabricating power MOSFET and electronic devices for operation from 300 K to 77 K. Devices made from Si suffer from carrier freeze-out below 77 K. Silicon carbide (SiC) is another material suitable for power switch transistors; however, SiC deivices suffer from carrier freeze-out at temperature higher than that of Si. SiGe heterostructure bipolar transistor (HBT) devices are good candidates for low temperature operation. However, SiGe HBT devices suffer changes in characteristics as the operating temperature gets colder. SiGe HBT device switching waveform of a dc-dc converter became distorted below 120 K.