hFEdegradation due to reverse bias emitter-base junction stress

Reverse bias stress of the emitter-base junction may degrade the hFEof a transistor when it is operated under normal bias conditions. The degradation mechanism exhibits no measurable temperature dependence and appears to be a surface effect. The junction characteristics exhibit no structure as a function of field plate voltage after stress. Pulse measurements indicate that the time required to induce degradation is less then 1.0 µs. Hot carriers appear to have an appreciable effect on the degradation. A mathematical model is presented to facilitate the comparison of degradation on devices with different initial current gains.