Schottky barrier diode

(electronics) A semiconductor diode formed by contact between a semiconductor layer and a metal coating; it has a nonlinear rectifying characteristic; hot carriers (electrons for n-type material or holes for p-type material) are emitted from the Schottky barrier of the semiconductor and move to the metal coating that is the diode base; since majority carriers predominate, there is essentially no injection or storage of minority carriers to limit switching speeds. Also known as hot-carrier diode; Schottky diode.

A metal-semiconductor diode (two terminal electrical device) that exhibits a very nonlinear relation between voltage across it and current through it; formally known as a metallic disk rectifier. Original metallic disk rectifiers used selenium of copper oxide as the semiconductor coated on a metal disk. Today, the semiconductor is usually single-crystal silicon with two separate thin metal layers deposited on it to form electrical contacts. One of the two layers is made of a metal which forms a Schottky barrier to the silicon. The other forms a very low resistance, so-called ohmic, contact. The Schottky barrier is an electron or hole barrier caused by an electric dipole charge distribution associated with the contact potential difference which forms between a metal and a semiconductor under equilibrium conditions. The barrier is very abrupt at the surface of the metal because the charge is primarily on the surface. However, in the semiconductor, the charge is distributed over a small distance, and the potential gradually varies across this distance. See also Contact potential difference.

A basic useful feature of the Schottky diode is the fact that it can rectify an alternating current. Substantial current can pass through the diode in one direction but not in the other. If the semiconductor is n-type, electrons can easily pass from the semiconductor to the metal for one polarity of applied voltage, but are blocked from moving into the semiconductor from the metal by a potential barrier when the applied voltage is reversed. If the semiconductor is p-type, holes experience the same type of potential barrier but, since holes are positively charged, the polarities are reversed from the case of the n-type semiconductor. In both cases the applied voltage of one polarity (called forward bias) can reduce the potential barrier for charge carriers leaving the semiconductor, but for the other polarity (called reverse bias) it has no such effect. See also Diode; Semiconductor; Semiconductor rectifier.