Dependence of Ideality Factor in Lateral PNP Transistors on Surface Carrier Concentration

The influence of surface carrier concentration on the ideality factor of excess base current (ΔI
_B
) in gated lateral PNP (GLPNP) bipolar junction transistors (BJTs) induced by 1-MeV electrons is investigated. ΔI
_B
in LPNP BJTs is impacted by the surface carrier density and radiation-induced interface traps. In GLPNP BJTs, the surface carrier concentration can be controlled by the voltage applied to a gate over the base region. The ideality factor changes after irradiation, and its dependence on emitter-base voltage (V
_EB
) is a function of gate voltage. For the irradiated devices, as the gate voltage decreases from +20 to -5 V, the ideality factor for excess base current changes from a single slope to two-slope behavior. The majority carrier concentration at the surface of the base, controlled by the gate voltage, impacts the excess base current and its ideality factor.