P-N Junction

When P-type and N-type semiconductors are placed together, the junction behaves differently than either type of material alone. Electric current will flow readily in one direction. This P-N interface we call the basic diode. The "P" (positive) side contains an excess of electron holes, while the "N" (negative) side contains an excess of electrons. Free electrons close to junction recombine with holes and this electron's movement form a potential difference across the junction. Diffusion of electrons and holes near to the junction lead to forming positive ions in the N region and negative ions in the P region. If the P-type is connected with the positive terminal and the N-type is connected with the negative terminal then the holes in the P-type region and the electrons in the N-type region are pushed toward the junction. They decrease the electric potential between the P side and the N side. The electrons can cross the P-N junction and its amount determines the amount of current that may flow through the diode. P-N junction is the base for the most semiconductor devices such as diodes, solar cells, LEDs, transistors and integrated circuits.