“Unlocking the Future: How a Simple Discovery Revolutionized Technology and Changed Our Lives Forever”
Ironically, the solution to this problem would ultimately be found in an older technology. As mentioned at the start of the video, early commercial radio sets used a device called a crystal detector to pick up radio signals. Also known as a cat’s whisker detector, this device comprised a crystal of lead sulphide or galena and a small spring called the cat’s whisker mounted on a pivoted handle. To use this type of radio, the user touched the cat’s whisker to various parts of the galena crystal until they found a spot that rectified the radio signal and allowed it to be heard over headphones.
As can be imagined, this device was finicky to use and took a great deal of practice to master. The crystal detector worked by forming a temporary metal-semiconductor junction, also known as a Schottky diode after its discover, German physicist Walter H. Schottky.
Galena, along with iron pyrite, carborundum, silicon, germanium, and several other substances, belongs to a class of materials known as semiconductors. Neither excellent conductors like most metals nor full-blown electrical insulators, semiconductors can have their electrical properties modified by treating or doping them with various impurities such as arsenic or phosphorus. Such doping produces either an N-type semiconductor, which has an excess of electrons in the outer shells of its atoms; or a P-type semiconductor, which has an excess of missing electrons – known as electron holes. Sandwiching a P and N semiconductor together produces a PN-junction. At the interface between the two semiconductors, the difference in electric charges causes a so-called diffusion current to flow, with electrons flowing from the N side to the P side and electron holes flowing from the P side to the N side. This in turn results in the formation of two adjacent layers of positive and negative change – known as the depletion region.
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