EMF induced in a $p$–$n$ junction under a strong microwave field and light

The effect of a strong electromagnetic field on currents and electromotive forces in a $p$–$n$ junction is considered. It is shown that a $p$–$n$ junction upon exposure to an electromagnetic wave becomes a source of electromotive force (emf) dependent on current. An analytical expression for the emf and internal resistance of such a source is derived. Dependences of the electromotive force and internal resistance on diode currents are obtained from the experimental current–voltage characteristic of a $p$–$n$ junction placed into a strong microwave (UHF) electromagnetic field.