content: Tubes were not complete circuits. They were merely components that were included in a circuit of two or more components. Vacuum tubes still have a role today as some high power applications are best made from tube components (such as magnetron tubes for microwave ovens) though there are up and coming solid state components aiming to replace them. Many semiconductor devices today do not use any silicon. There are many more semiconductor materials that are better suited for modern integrated circuit and other semiconductor device manufacturing such as Gallium Arsenide, Cadmium Selenide and fused quartz substrates. LEDs use these more exotic substrates like GaAs GaInP and GaAlInP because they allow for crystal formations that produce visible and invisible light output with relatively low power requirements. As for tubes, a new variety of vacuum tube technology has come around in the last decade. The Japanese synthesizer manufacturer Korg teamed up with vacuum fluorescent display maker Noritake to produce the NuTube. The NuTube is a low power, small size vacuum tube equivalent that is made using the same processes as vacuum fluorescent displays. They can bring the warmth and smoothness that older vacuum tubes did to audio applications, hence Korg's interest in making the devices. They are also impervious to radiation which make them ideal for use in space applications which would destroy non-hardened semiconductor devices. Tubes are far from dead.