Cj. Huang et al., TEMPERATURE-DEPENDENCE OF HOT-ELECTRON DEGRADATION IN BIPOLAR-TRANSISTORS, I.E.E.E. transactions on electron devices, 40(9), 1993, pp. 1669-1674
Bipolar transistors were electrically stressed at -75, 175, and 240-de
grees-C for 1000 h with a constant reverse-bias voltage applied to the
emitter-base junction. Degradation of the base current and the curren
t gain was observed. The rate of degradation was found to be temperatu
re-dependent with a larger degradation occurring at the lower temperat
ure. This temperature dependency is studied using an electron energy s
imulation technique and experimental data on degradation and post-degr
adation annealing. From the electron energy simulations, the number of
hot electrons above a damage threshold energy was seen to increase wi
th increasing ambient temperature at a constant reverse-bias voltage.
This increase with temperature occurred because higher stress currents
dominated over a reduction in the electron mean free path between col
lisions at higher temperatures. However, an actual degradation rate re
duction at higher temperatures occurs because of simultaneous annealin
g of the states produced by hot electrons. A model is developed to des
cribe the temperature dependence of degradation and post-degradation a
nnealing.