When driving at night, the headlights of cars can appear blindingly bright. Part of the issue lies in the fact that many cars today stand higher off the road, so that even dipped headlights can dazzle drivers in smaller cars like mine. But this is not the whole story. A bigger problem lies in the quantum devices used to generate the light in many modern vehicles – LEDs, or light-emitting diodes – and in the quantum and other processes responsible for detecting the light in my eyes.
But what is a diode, and why does it emit light? Briefly, semiconducting materials like silicon can be ‘doped’ by adding small amounts of impurities. Doping with a group 5 element results in additional free electrons, creating an n-type (negative) semiconductor. Doping with a group 3 element means an electron is ‘missing’, and the resulting ‘hole’ can travel through the crystal lattice as if it were a positive charge, creating a p-type (positive) semiconductor.
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