The forward characteristic of the pin diode

A theory is given for the forward current-voltage characteristic of the PIN diffused junction silicon diode. The theory predicts that the device should obey a simple PN diode characteristic until the current density approaches 200 amp/cm². At higher currents an additional potential drop occurs across the middle region proportional to the square root of the current. A moderate amount of recombination in the middle region has little effect on the characteristic. It is shown that the middle region cannot lead to anomalous characteristics at low currents.