Degradation of hFEat moderate current levels

Degradation of moderate current h
FE
under high-temperature reverse bias has been noted in 20-30 percent of the n-p-n transistors examined in this study and this type of degradation is shown to be accompanied by a decrease in neutral region minority carrier lifetime within the active base. It has been found that n-p-n's which have degraded can be partially, and in some instances, completely recovered by increasing V
CEO
significantly beyond BV
CEO
. P-n-p transistors examined in this study did not exhibit this type of h
FE
degradation. This mechanism is distinct from both ionic contamination induced degradation of h
FE
as well as avalanche degradation of h
FE
and represents, at present, an unexplained degradation mode for bipolar transistors.