Who Invented LEDs?

Nick Holonyak, 1962

In our quest to make the darkness light, we have tried all sorts of technologies, from campfires to candles to oil lamps, from electric arcs to incandescent globes to neon lights to fluorescent tubes. The ideal light source would be cheap, efficient, robust, long lasting and versatile. Light emitting diodes (LEDs) may provide the ideal.

American Nick Holonyak produced his first LED, which made red light, in 1962 while working for General Electric. An LED is cousin of the transistor semiconductors are impregnated with impurities to create an excess of negatively charged electrons or positively charged ‘holes. As a current passes across the junction between N-type and P-type material, holes and electrons combine to liberate energy as light. The color of the light depends on the material used. The easiest radiations to produce, and the first to reach the market, were red and infrared (heat). Yellow, green, blue and even ultraviolet light came later (and are more expensive). White light comes from mixing various colors or by making suitable materials glow (fluoresces) by bathing them in ultraviolet light from an LED.

LEDs seem to have all the advantages. Individual units are small but intensely bright and can be clustered for increased light output. LEDs are long lived; typical LEDs will last 10 years, far longer that other light source. LEDs give off much less heat than incandescent globes (that is, they are twice as good as turning electricity into light) and are more compact and robust than florescent tubes (which are, however, more efficient). The impediment remains cost, and that is coming down rapidly as manufacturing techniques improve.

You are already encountering LEDs every day-in your TV remote control (which uses infrared) and your optical mouse, in the dashboard of your car, in the increasingly common, lightweight message display in new style traffic lights and flashlights. In time they are likely to replace all other forms of lighting for everyday purposes, car headlamps are likely to be the next application. And new generations of technology- light-emitting transistors and transistor lasers- are still to make their mark.