Radiation-induced gain degradation in lateral PNP BJTs with lightly and heavily doped emitters

Abstract

Radiation-induced gain degradation is compared in two types of lateral PNP bipolar devices that are identical except for the emitter doping. The devices with heavily-doped emitters (1/spl times/10/sup 20/ cm/sup -3/) degrade less than the devices with lightly-doped emitters (1/spl times/10/sup 18/ cm/sup -3/). Both device types are sensitive to interface-trap formation in the oxide above the emitter-base junction and the neutral base region. In addition, the devices with lightly-doped emitters experience spreading of the depletion region into the emitter, increasing their sensitivity to total-dose irradiation. The gain degradation in both device types is due to a combination of increased base current and decreased collector current. The radiation-induced decrease in collector current is more significant for devices from this technology than for other devices studied previously. Increased gain degradation is observed in heavily-doped devices irradiated at low dose rates, but the enhanced degradation appears to be due to time-dependent effects rather than true dose-rate effects. The lightly-doped devices do not exhibit a clear dose-rate trend and the gain of these devices improves during post-irradiation annealing.