P-N Junction ‒ Forward Bias

PN junction is the base for the most semiconductor devices such as diodes, solar cells, LEDs, transistors and integrated circuits. The diode allows or prevents current through the lamp, depending on the polarity of the applied voltage. When the polarity of the battery is such that electrons are allowed to flow through the diode, the diode is forward-biased. The external voltage would tend to cause the movement of electrons from the negative terminal of the supply through the diode and back to the positive terminal. It leads to injection of electrons into the N-type material. This increases the number of electrons and therefore reduce the depletion layer. The positive terminal pulls electrons from the P-type material. This increases the number of holes, reducing the depletion layer as well. The external voltage reduces the barrier voltage and if the applied voltage is greater than the barrier voltage it will overcome it and produce a current flow through the diode.