Abstract
The influence of the emitter-base junction surface property on current gain (hFE) and on its degradation at moderate current levels has been investigated. Various transistors with different emitter perimeter-to-area ratios (LE/AE) ware fabricated on one wafer with SiO2 or Si3N4 junction passivation. The influence of the emitter-base junction surface recombination current on the hFE is analyzed by referring to the hFE-1 vs. LE/AE relation. The influence on hFE degradation is also analyzed by monitoring changes in the hFE-1 vs. LE/AE relation during accelerated life tests. It is shown that the hFE of high frequency transistors, whose fT was several GHZ, decreases to about 50% of that of surface influence independent transistors. Surface recombination current change is a major factor in inducing the hFE change during life tests.
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