Three years later and here is your answer! Semi-conductors are not used as wires. They are not as conductive as convential conductors, such as metals, and also far more expensive to scale to the length of wire you would need. But, they have different extremely useful properties that are used to perform many other electronic tasks. In this video, he explains how a PN junction can function as an electrical component called a diode, which is an electronic device that only lets current flow in one direction. This alone is an extensively in electronic circuits. As mentioned in the video, you can now turn AC power into DC power. Whereas a conductor, such as wire, will always just let current flow in both directions. A diode can also be used in electrical protection circuits. For example, if you connected a battery the wrong way round to a device, a diode could be used to make sure only that only when the battery is wired the correct way round that current can flow. Therefore protecting your circuit. PN junctions can also be used to create light emitting diodes (LEDs) which is a light emitting device, which produces light far more efficiently than simply heating up a conductor until it glows does. Most importantly, using PNP or NPN junctions, you can also form transistors, which are electronically controlled switches and can also act as amplifiers. Transistors are the basis of every electronic device in modern day. Your phone, computer, calculator uses millions if not billions of transistors to perform logical operations. And each transistor, is built up of a structure of differently doped semi-conductors. Hope this explains the difference and importance of semi-conductors compared to regular conductors! In essence, one is for moving electricity around, and the other, is used to carry out useful operations. A semi-conductor can function as very bad and very expensive conductor, but a conductor can not do what a semi-conductor does.