Diode is off, circuit evolves toward steady state. During this time, a reverse voltage is built over the diode. Therefore, space charge has to be provided. Switching Time of a Diode Turn-off Transient. Switching Time of a Diode Turn-on Transient.
Similar considerations hold for the turn-on transient.
Not all of the applied bias voltage falls across the junction, some falls across the neutral regions. This is usually modeled with a series resistance at the contacts. The thermal equilibrium carrier concentrations increase with increasing temperature causing I S to increase. C. These have a dramatic effect on the operation of a device. The increase in leakage current through reverse-biased diodes decreases isolation quality.