Rebound effect in power VDMOSFETs due to latent interface-trap generation

The rebound effect, observed in commercial n-channel power VDMOSFETs during biased thermal annealing, following gamma -radiation exposure, is analysed. Rebound is caused predominantly by ´latent´ interface-trap generation, which occurs in transistors irradiated and annealed with positive bias applied to the gate, after initial apparent saturation of the interface-trap density. Latent, interface-trap buildup may cause difficulties in predicting device response in low dose rate environments, such as space.