A Schottky diode, sometimes called a hot carrier diode, is a type of semiconductor diode. Like all diodes, it allows current to flow freely in one direction but blocks most current flow in the other direction. The Schottky diode differs from other diodes in its construction. Instead of transferring current between two semiconductors, a Schottky diode's active junction is between a metal and a semiconductor. This design results in lower forward voltage drop and faster switching action, which makes the Schottky diode ideal for use as a rectifier, mixer, or detector diode.
Standard semiconductor diodes are made of two bits of semiconductor material joined together. One bit is full of electrons and is called the n-zone. The second bit has fewer electrons and is called the p-zone. The current flows over the connection point, which is called the p-n junction, from the n-zone to the p-zone. In a Schottky diode, a small piece of metal is attached to a single semiconductor to form a Schottky barrier, and it is over this barrier that current flows.
The contact point through which current can flow is larger in the Schottky barrier than it is in a p-n junction. The advantage to this design is lower forward resistance. It takes less energy for the current to move through the diode, which means the forward voltage drop is smaller. The forward voltage drop is the change that results whenever an electrical current passes through a diode. A standard silicon diode has a forward voltage drop (Vf) of 0.7 to 1.7, while a Schottky diode has a Vf of no more than 0.5.
Another major advantage of the Schottky diode is its fast switching action. When a diode switches from moving current to not moving current, this is known as switching. It takes nanoseconds and causes a small amount of electromagnetic interference noise, which temporarily degrades radio signals. The faster switching action of the Schottky diode causes less electromagnetic interference, making this type of diode ideal for use in radio applications.
The most common use of this type of diode in radio systems is as a rectifier. Rectifiers process AC (alternating current) signals and turn them into DC (direct current) signals. This is how information is extracted from signals for AM radios. Schottky diodes may also be used as mixer diodes to convert from higher frequencies to lower frequencies or as detector diodes to convert microwave signals to video signals.
Though the invention of the Schottky barrier and diode are often attributed to Walter H. Schottky, he did not actually create the electronic components. Schottky was a German physicist working in Berlin in the early 1900s. He developed a formula for the interaction energy between a point of charge and a piece of metal. This formula eventually led to the creation of the barrier and diode that bear his name.