A Schottky diode has a metal-semiconductor junction, resulting in lower forward voltage drop and faster switching action. It is ideal for use as a rectifier, mixer or detector diode in radio systems. The diode was not invented by Walter H. Schottky, but his formula led to its creation.
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, the active junction of a Schottky diode is between a metal and a semiconductor. This design results in lower forward voltage drop and faster switching action, making the Schottky diode ideal for use as a rectifier, mixer or detector diode.
Standard semiconductor diodes consist of two pieces of semiconductor material joined together. One bit is filled with electrons and is called zone n. The second bit has fewer electrons and is called the p-zone. Current flows through the connection point, called the pn junction, from zone n to zone p. In a Schottky diode, a small piece of metal is attached to a single semiconductor to form a Schottky barrier, and it is across this barrier that current flows.
The contact point through which current can flow is larger in the Schottky barrier than in a pn junction. The advantage of this design is less forward resistance. It takes less energy for current to move through the diode, which means the forward voltage drop is less. Forward voltage drop is the change that occurs each time an electric 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 no greater than 0.5.
Another major advantage of the Schottky diode is its fast switching action. When a diode switches from moving current to non-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 transform them into DC (direct current) signals. This is how information is extracted from signals for AM radios. Schottky diodes can also be used as mixer diodes to convert higher frequencies to lower frequencies or as detector diodes to convert microwave signals to video signals.
While the invention of the Schottky barrier and diode are often credited to Walter H. Schottky, he didn’t 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.
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