Hello. Suppose we have a MOS capacitor (n-substrate). When we give negative voltage the majority carrier (electrons) are repelled from the oxide-substrate interface and move towards the bulk. Say the bias is -0.3 volts. The substrate is depleted and in steady-state. Suddenly if the bias is changed from -0.3 to -0.6, I know that the width of depletion region will increase definitely. My question is how long will it take to reach the new steady state? Does it depends on some form of life time or response time? I found typical example in text books for optical step excitation where they showed (1-exp(t/tao)) like shape to reach steady-state. How can I model the movement of majority carriers (electrons) under step bias? Please give me some information. Thanks. M. Satter.