semiconductor diode

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A diode made of semiconductor components, usually silicon. The cathode, which is negatively charged and has an excess of electrons, is placed adjacent to the anode, which has an inherently positive charge, carrying an excess of holes. At this junction a depletion region forms, with neither holes nor electrons. A positive voltage at the anode makes the depletion region small, and current flows; a negative voltage at the anode makes the depletion region large, preventing current flow.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.


What is a semiconductor diode?

A semiconductor diode is a diode made of semiconductor material, most often silicon. It’s kind of like a door for electricity to move through, but it only opens one way.

A diode is a device for controlling electrical currents so that they only flow the desired way (the way the engineer wants them to). A semiconductor is a material that electricity can travel through, but not as well as when it travels through a stronger conductor like copper.

Most diodes in use today are semiconductor diodes. People often simply use the word diode when they are talking about a semiconductor diode.

Why are semiconductor diodes important?

If you’re reading this, thank a semiconductor diode.

Semiconductor diodes are used in all sorts of modern electronics, including the processors in phones and computers. The concept was first discovered by German physicist Ferdinand Braun in 1874, but it didn’t take off until the advent of radio in the early 1900s. The first commercial semiconductor diodes were devices known as crystal detectors, patented in 1906 by American electrical engineer Greenleaf W. Pickard, who marketed them for radio applications. The most common type of crystal detector used a thin, springy metal wire, giving rise to its popular name: the cat’s whisker detector.

Among the simplest semiconductor devices are those known as p-n junction diodes. Most of the time, they’re made of silicon, though germanium is also used. Silicon doesn’t conduct very well on its own, but its conductivity can be improved by adding other elements. Depending on what you add to the silicon, it can become either what’s called a p-type material, which has a positive charge, or an n-type material, which has a negative charge.  To create the diode, some p-type material and n-type material are put together. The p-type is the anode, and the n-type is the cathode.

At the junction, where the two materials meet, they cancel each other out, and the area around the junction doesn’t have a charge. The electrical current can’t cross it. If you add a positive electrical current to the positive end and a negative one to the negative end, the junction gets smaller and electricity can flow across the junction. But if you reverse that, the junction gets bigger and the current can’t go across. So electricity can only be conducted in one direction, and the diode is created.

Another basic type of diode is the thermionic diode. You might know these better as vacuum tubes. Vacuum tubes use glass tubes to create a vacuum surrounding a tiny wire, which heats up the cathode and releases electrons. The anode then attracts the electrons, which means the current goes in that direction. Though this type of diode was common in early electrical applications, it’s largely been replaced by the semiconductor type today.

Semiconductor diodes are used all around us in the many, many electronic devices that we rely on for modern life. For instance, diodes are used in surge protectors (which keep all kinds of devices from being fried). These types of diodes open only when the voltage is too high and let out the extra to protect your device from receiving too much electricity.

Did you know … ?

LED (as in LED lights) stands for light-emitting diode.

Semiconductor diodes are so flexible and powerful that they can be made to produce light, and that light is much more efficient than what is emitted from standard light bulbs.

What are real-life examples of semiconductor diodes?

Semiconductor diodes might sound complicated, but they’re based on simple principles. You can find them in most of the electronics you use every day.

What other words are related to semiconductor diode?

Quiz yourself!

True or False?

Most diodes are semiconductor diodes.

How to use semiconductor diode in a sentence