High-energy radiation effects on subthreshold characteristics, transconductance and mobility of n-channel MOSFETs

The influence of 8 MeV electrons on the threshold voltage (V_TH), transconductance (g_m) and mobility (μ) of n-channel depletion metal–oxide semiconductor field-effect transistors (MOSFETs) irradiated at gate bias, V_GS = +2, 0 and −2 V, has been studied in the dose range of 0.5–31 kGy. The measurements performed after irradiation showed considerable decrease in V_TH, g_m and μ. The densities of interface trapped charge (ΔN_it) and oxide trapped charge (ΔN_ot) for irradiated devices have been estimated from the subthreshold measurements. It has been found that ΔN_ot is higher than ΔN_it. The mobility of carriers (μ) in the n-channel was estimated from the peak transconductance (g_mPeak) and it was found that μ decreased by around 68.5–73.5% after exposure to the total dose of 31 kGy. Mobility degradation coefficients due to interface traps (α_it) and oxide trapped charge (α_ot) were estimated and it was found that the mobility degradation was mainly due to ΔN_it and the effect of ΔN_ot was negligible.