Degradation of hFEat moderate current levels

Degradation of moderate current hFEunder 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 VCEOsignificantly beyond BVCEO. P-n-p transistors examined in this study did not exhibit this type of hFEdegradation. This mechanism is distinct from both ionic contamination induced degradation of hFEas well as avalanche degradation of hFEand represents, at present, an unexplained degradation mode for bipolar transistors.