Experimental studies of collector-emitter voltage bias influence on the total ionization dose effects in NPN Si BJTs

摘要

The voltage V-CE, bias influence studies on total ionizing dose (TID) in bipolar junction transistors (BJTs) were investigated. The BJTs were set at forward active mode of base-emitter voltage (V-BE) swept from 0 to 1.0 Vat different biased conditions of V-CE, ranging from 1 V to 2 V at an interval of 0.25 V during Co-60 gamma irradiation. The damage mechanism of TID in BJTs at different V-CE bias conditions were analysed by forward Gummel characteristics, forward current gain (beta(f)), normalized excess base current (Delta I-B/I-Bpre), normalized excess collector current (Delta I-C/I-Cpre), normalized current gain (beta(fpost)/beta(fpre)), ideality factor (n) and power dissipation (P-d). The results show that the increments of base current (I-B) and collector current (I-C) are slightly different in various V-CE bias conditions which also effects slight changes in their current gain (Delta beta(f)) degradation. The current gain degradation (beta(f)) at high bias V-CE degraded more slightly than low bias V-CE. The Delta I-B/I-Bpre , Delta I-C/I-Cpre and beta(fpost)/beta(fpre), estimated shows similar trend of different V-CE bias conditions resulting into varying distribution of performance degradation of the BJT. The ideality factors (n) for excess base current (Delta I-B) were similar to 2 for V-BE from 0.35 V to 0.6 V at different V-CE bias conditions. Thus, ideality factor (n) slightly increases as the V-CE bias rises and decreases with the increased accumulated total dose level after the n peak value was obtained at TID equals to 130 krad (Si) for irradiated BJTs. Finally, the power dissipated (P-d) by BJTs were compared as V-CE = 2 V 1.75 1.5 V 1.25 1 V and were noted to be more effective at V-BE 0.6 V which also concur with temperature rise T-R. The T-R in BJTs resulted into self-heating effects.