The behavior of commercial power Vertical-Double-Diffused Metal Oxide
Semiconductor Field Effect Transistors (VDMOSFETs) during gamma-ray
irradiation and subsequent annealing at room and elevated temperature was
investigated. The densities of radiation-induced fixed traps and switching
traps were determined from the sub-threshold I-V curves using the midgap
technique. It was shown that the creation of fixed traps dominated during
irradiation. The experimental results have also proved the existence of
latent switching traps buildup process during annealing at an elevated
temperature. This increase correlated with the decrease in fixed trap
density. Physical and chemical processes responsible for the threshold
voltage shift during irradiation have been analyzed on the basis of
interactions between secondary electrons released by gamma photons with
covalent bonds Sio - O and Sio - Sio. H-W model has been used for the
explanation of processes leading to latent switching traps buildup at an
elevated temperature and its passivation at late annealing times.