Schottky barrier
From ArticleWorld
A Schottky barrier is a junction between a metal and a semiconductor, which exhibits rectifying characteristics. This concept is used in making Schottky diodes. Schottky diodes have low forward voltage drop and an extremely fast switching action. They have forward voltage drops of about 0.3 volts, as compared to 0.6 volts in silicon diodes, which use adjacent p-type (positive) and n-type (negative) semiconductors. This is due to the greater current density which is present in diodes with a Schottky barrier.
Schottky devices also possess fast switching, because only one semiconductor is used and no time is lost in recombination of majority and minority carriers when conduction is to be halted. This also results in smaller devices, making these diodes useful in switch-mode power converters operating at high frequencies.
Advantages of Schottky barriers over p-n junction diodes
Schottky devices possess fast switching, because just one semiconductor is used. Thus smaller devices can be manufactured. Lower resistance devices are produced since one of the materials used is a metal.
Applications in modern technology
The concept of Schottky barrier is used in bipolar junction transistors, also known as Schottky transistors. Such transistors are prevented from excessive saturation since the junction voltage of the Schottky barrier is low. Also, the switching speed being high brings about a crucial advantage. The metal-semiconductor field effect transistor (MSFET) uses a reverse biased Schottky barrier for its operation. The High Electron Mobility Transistor (HEMT) utilizes a heterojunction along with a Schottky barrier resulting in greatly improved conductance as compared to the MSFET. Schottky diodes such as the 1N5817 are used widely in electronics. The Schottky barrier is used in the 7400 series of logic devices to utilize their higher switching speeds and lower junction voltages.
High frequency switch-mode power converters operating at 1MHz and RF detectors and mixers (operating up to 5 GHz) are other applications of Schottky barriers.