Electrical probing of surface and bulk traps in proton-irradiated gate-assisted lateral PNP transistors

The effects of 46 MeV proton irradiation-induced trap generation and its impact on the electrical characteristics of gate assisted lateral PNP transistors (GLPNP) are investigated for the first time. At proton fluence as high as 10¹² p/cm² the devices show a negligible current gain degradation, and at 10¹³ p/cm ² the devices are still functional. The excellent radiation hardness is attributed to the much thinner gate oxide than in conventional lateral PNPs and its gate assisted operation. By changing the gate bias, and modulating the surface status from accumulation to inversion, the surface traps can be electrically probed from the I-V characteristics. A base current peak is observed after radiation, and is understood using 2D device simulation to be a result of the increase in oxide charge and surface trap density, in conjunction with the different SRH recombination rate limiting mechanism in presence of high density traps. The inverse mode operation is shown to be a useful tool for probing the bulk traps