Reverse Bias
When the diode is reverse-biased, a very small drift current due to thermal excitation flows
across the junction. This current (reverse saturation current, I0) is given, according to the
Boltzmann equation, by the formula:
where K0 is a constant depending on the pn junction geometry and V0 is the built-in voltage
of the diode (see chapter “Semiconductor Materials: pn junction”).
Forward Bias
When the diode is forward-biased through a voltage V , a small drift current flows againacross the junction. In that case, however, there is an additional component, the diffusion
current Vd, given by the formula:
