Schottky diodes

Schottky diodes - Initial characteristics

A Schottky diode, also known as a barrier diode or hot carrier diode , is a semiconductor diode formed by combining a semiconductor (generally silicon) with a metal. It is characterized by a low voltage drop in the forward direction (approximately 150 mV - 500 mV compared to 600...700 mV typical for a junction silicon diode) and very fast signal switching . The crystal detectors used in the early days of radio communications and the metal-selenium rectifiers used in early DC power supplies can be considered the first primitive Schottky diodes.

Structure of a Schottky diode

A barrier junction is created in this diode between the metal and the semiconductor, creating the so-called Schottky barrier. Common metals used are molybdenum, platinum, chromium or tungsten; the semiconductor is usually N-type silicon. The metal side is the anode and the silicon is the cathode. The choice of metal and semiconductor combination determines the forward voltage of the diode. The metallic layer is typically deposited on a semiconductor substrate using physical vacuum deposition methods. Due to the small thickness of the metallic layer and the fact that it also serves as an ohmic contact for the anode, diodes of this type are usually less resistant to breakdown and generally less durable than classic junction diodes. The barrier junction is in direct contact with the temperature-sensitive metallization, therefore a Schottky diode can dissipate less heat than an equivalent PN equivalent of equivalent size.

Shottki diode - Principle of operation

Unlike junction diodes, the Schottky diode is a majority-carrier device - only electrons, the excess of which is in the N-type semiconductor, which is the cathode of the element, act as carriers of electric current in this semiconductor device. The metallic anode is electrically neutral. The biggest difference compared to diodes with a PN junction is the regeneration time when switching from the conducting state to the barrier state. In a Schottky diode it is much shorter due to the fact that there is no depletion region at the junction. Due to this, the regeneration time in a Schottky diode ranges from several hundred picoseconds to several dozen nanoseconds, while in ordinary PN diodes it ranges from 100 ns to several microseconds.

Typical applications of Schottky diodes

Schottky diodes are used in many specific applications that take advantage of their unique parameters. A typical application of these elements are impulse converters . Low forward voltage and fast recovery time lead to increased power supply efficiency. Due to the low voltage drop, they are also used to connect redundant power sources and as rectifying diodes in impulse converters . Due to the high current density, these elements are also useful in overvoltage protection systems on sensitive inputs .