Experimental Investigation of the Effects of Reactor Neutron-Gamma Pulse Irradiation on SiGe HBTs Under Different Bias Conditions

The degradation characteristics of silicon-germanium heterojunction bipolar transistors (SiGe HBTs) under different bias modes (forward, cutoff and saturation) during irradiation were reported after multiple pulsed neutron-gamma irradiation at room temperature. The radiation-sensitive parameters of the test samples, including base current I
_B
, collector current I
_C
and DC current gain
$\beta $
, were measured and compared before and after every reactor n-
$\gamma $
pulse irradiation. The test results show that I
_B
increased with increasing fluence, and I
_C
slightly increased in the low base-emitter voltage V
_BE
region (approximately from 0.4 V to 0.5 V) and decreased in the high-V
_BE
region (approximately V
_BE
>0.5 V). Moreover, the degradation degree of the test samples was different under different bias conditions. The performance of the test samples under cutoff bias mode displayed the most serious degradation, while those under forward bias mode suffered minimum damage. Meanwhile, the time-dependent annealing characteristics of the DC current gain for SiGe HBTs at various bias conditions were compared and analyzed.