When a negative voltage is applied to the p-type of the diode (reverse bias), it increases the depletion zone and prevents current from flowing. See diode. Built like two diodes in a row (three PN ...

Long- and short-base diodes, Recombination and generation in the depletion region, Non-ideal current, Effect of band alignment, and Diffusion and thermionic emission currents. In this module on ...