Gallium arsenide

Gallium arsenide, GaAs, is a semiconductor made of gallium and arsenic atoms in equal numbers. Like silicon, it can be made to conduct or block current, but it has two big advantages: it turns electricity into light efficiently, and electrons race through it several times faster than through silicon.

It is made by combining gallium and arsenic at high temperature in a sealed, pressurized furnace, since the arsenic would otherwise boil away. The melt, at about 1,240 °C, is grown into a single large crystal, either by slowly pulling a seed upward through a layer of molten boron trioxide that keeps the arsenic in, or by freezing it slowly from one end inside a crucible. The crystal is sliced into wafers and polished, and thin layers with carefully chosen impurities are grown on top to make devices.

In the TV's remote, a tiny chip of it is the glowing heart of the infrared LED. Elsewhere it powers the radio amplifiers in phones and the high-efficiency solar cells on satellites. It costs more than silicon and is more brittle, and arsenic is toxic, so factories handle it with great care.