Solid State Devices

A solid-state device is an electrical component or system that's based largely or entirely on a semiconductor. The phrase became more prevalent in the late 50s when vacuum tube technology was getting phased out and replaced with transistors and semiconductor diodes.

In solid-state devices, the current flowing through a circuit is confined to the solid compounds specially designed to amplify and switch it. There are two ways to think about how current flows – as the flow of positive charge carriers known as “holes” (created by the absence of an electron) , or the flow of negative charge carriers (electrons). The prevalence of holes and electrons can be controlled through doping, which influences the function of the solid state device. The technology of doping is what gave rise to integrated circuits.

Scientists discovered that electrons have the uncanny ability to form a barrier on the surface of certain semiconductor crystals such as silicon, germanium, gallium, and arsenide under the right conditions. By manipulating this barrier, they were able to control the flow of current through the crystal, which then allowed them to build a gadget (solid-state device) that could perform the electrical operations that were previously done by vacuum tubes.

They later named this device “transistor” – a combination of the words “transfer” and “resistor” (although some sources suggest the origin was a combination of “transductance” and “varistor”). Transistors are semiconductor devices used for generating, controlling, and amplifying electrical signals. They’re used in detectors, modulators, oscillators, and virtually any electronic apparatus you can think of.  Engineers later applied ideas from solid state devices to build other components such as capacitors and resistors.

The use of solid-state devices in building electronic components proved to be less expensive, more reliable, smaller, and sturdier compared to their vacuum tube predecessors. Since electrical circuits could now be made smaller than ever, the hardest part became figuring out the awkward wiring between the various components.

Modern-day applications of solid-state devices include Light-Emitting Diodes (LEDs), Integrated Circuits (ICs) and even solar cells. Semiconductors are at the heart of these technologies and have become the “nerve cells” of the digital age.