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 (Δ N it ) and oxide trapped charge (Δ N ot ) for irradiated devices have been estimated from the subthreshold measurements. It has been found that Δ N ot is higher than Δ N 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 Δ N it and the effect of Δ N ot was negligible.