Silicon-Germanium Bipolar Technology for Enabling Cold-Capable, Radiation-Tolerant Electronics for Spacecraft

The objective of this research is to investigate the effect that low temperature has on the radiation effects on advanced silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) for the application of deep-space exploration missions that are specifically classified as extreme low-temperature and highly radiation active environments, such as Jovian exploration missions. We designed a unique experimental testbed that enabled DC and RF measurements to be taken in situ at various temperature and radiation points. The experiment was conducted at the Jet Propulsion Laboratory (JPL) where low-temperature and radiation environments can be mimicked. We showed that while there is some radiation damage in base leakage current on the single transistor level, there is no observed damage due to total-ionizing dose (TID) in noise figure, linearity, or gain for a 2.4 GHz low-noise amplifier (LNA) that was irradiated at an ambient temperature of about 100 K up to 1 Mrad (Si). Furthermore, we confirmed the notion that radiation at lower temperatures yields less damage and showed why it is important to separate temperature-dependent performance with measurable radiation damage at different temperatures. We also took a simulation approach to determine whether single-event transients (SETs) get worse as a result of the device being in low ambient temperatures. For a single standalone device, the results show that the transient gets larger in magnitude but shorter in duration. However, the circuit results show that the effects of an SET get worse in some cases with low temperatures such as in the context of LNAs, but can also get better in other cases such as current-mode logic (CML) D-flip-flops.M.S