Temporary Neutron Damage in Transistors

The amount and duration of temporary neutron damage were measured in a wide variety of types of transistors at the White Sands Pulsed Reactor. They all shoed a decrease in the large-signal common-emitter current gain lasting about one second. Half of the damage recovered in a time of 0.0002 to 0.05 sec, for different types, and the ratio of the peak damage (just after the burst) to the permanent damage varied from 1.5 to 3. The amount and duration of the effect were much smaller in samples operated at relatively high junction temperatures. A model is proposed to explain the effect on the basis of the kinetics of the trapping and recombination processes occuring, in a pnp transistor, for example, lattice + radiation ko ¿ ¿ K5 T T + n k1 ¿ ¿ K2 T- T- + p k3 ¿ ¿K4 T where T- and T signify loaded and unloaded traps, and n and p electrons and holes, respectively. The recovery of the gain is not first order, so that the k3 reaction alone does not dominate the recovery. The k5 annealing reaction is observed well above room temperature. The main reactions involved in the recovery are the k2, k3 and k4 reactions. On the assumption of a first order reaction, the activation energy was found to be ~ 0.11 ev. Deviations from first order were attributed to a net second order reaction with a very small activation energy. The value ~ 0.