Two-colour LED Could Lead to Better Screens

From New Scientist - Latest Headlines:

A silicon LED that can quickly switch between emitting red and blue light could ultimately be the basis for higher resolution displays. LEDs can normally only emit light of one colour. A new study shows that adding a certain rare earth metals can allow them to switch between two colours. The new LED is made from a layer of semiconducting silicon and a layer of insulating silicon dioxide. This creates a 100-nanometre-thick barrier that obstructs the flow of electrons. Europium, a rare earth metal, is then implanted within the silicon dioxide. Applying a voltage across the silicon dioxide barrier allows the electrons to cross the barrier - a quantum mechanical process known as "tunnelling." While tunnelling through the silicon, the electrons sometimes smack into the europium atoms, which sends them to a higher energy state. When these atoms fall back to their original state, they emit light.

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