Degradation Analysis of Lateral PNP Transistors Exposed to X-Ray Irradiation

Degraded current gain by X-ray irradiation is analyzed for lateral pnp transistors. The relationship between the total dose of X-ray and the surface recombination velocity is also studied. Surface recombination velocity is evaluated in two regions: the depletion region of the emitter-base junction and the non-depleted charge-neutral region of the base surface. X-ray total dose dependency of surface recombination velocity is experimentally derived as: sdep = 0.33D0.9 for depletion regions, and sSur = 3.8D0.8 for non-depleted surface region in the device structure. A radiation hardened structure with a surface potential barrier for lateral pnp transistors is proposed. The possibility of more than one-order of magnitude improvement in radiation hardness is demonstrated by both simulation and experiments.