Anomalous Photocurrents in Low-Power Epitaxial Transistors

In this paper, we give additional experimental results concerning the anomalous photocurrent problem. Anomalous photocurrents were observed in various epitaxial NPN transistors for different operating modes and bias voltages. It is particularly shor that the devices switch on a stable I(V) characteristic that agrees closely with that given by the avalanche injection mode obtained experimentally with a fast rising high current pulse generator. The triggering mechanism is investigated and emitter injection is found to be a necessary condition. This experimental approach allows us to predict accurately the anomalous photocurrent value without radiation tests and seems to be quite useful in hardening studies.