Bias effects on total ionizing dose radiation response of NPN silicon-germanium hetero-junction bipolar transistors

Background: Silicon germanium hetero-junction bipolar transistors (SiGe HBTs) technology has been considered to be one of the promising candidate for future space applications due to its exciting built-in tolerance of total ionizing dose (TID) radiation and displacement damage (DD) performance. Purpose: The bias effects on total ionizing dose radiation response of the NPN commercial SiGe HBTs produced domestic were investigated with the ⁶⁰Co γ ray under the different bias of Emitter-Base Junction. And the potential mechanisms of the different responses of the radiation under different bias are analyzed. Methods: The devices were mounted in the irradiation boards with different bias conditions during the irradiation and annealing process, and irradiated to a maximum total ionizing dose level of 11 kGy(Si). The electrical parameters including Gummel characteristics and direct current gain of the devices were measured with Keithley 4200-SCS Semiconductor Parameter Analyzer removed from the irradiation room within 20 min at room temperature before and after each specified value of accumulated dose. Results: The radiation sensitive electric parameters of the SiGe HBTs are base current and current gain. And, the damage of the devices with reverse bias is greater than that of zero bias, the degradation of the forward bias is the smallest. Conclusion: The difference of the radiation response under different bias conditions are due to the different amounts of the oxide and interface trap charge induced by the radiation under diverse electric field. (authors)