Visible Light-emitting Diodes: Past, Present, and Very Bright Future
Craford, M. George*
MRS bulletin 25, no. 10 (2000): 27-31
https://doi.org/10.1557/mrs2000.200
* Draper Prize Winner
“In 1907, a man named Round took a piece of carborundum, which is silicon carbide, ran a 10-V current across it, and saw all the colors I will be mentioning later. That discovery occurred nearly a century ago; yet, not much further research into this phenomenon was done until 1960.
In 1960, Holonyak, who was then at General Electric, started researching compound semiconductor alloys. He and others had been working with gallium arsenide (GaAs), which is a direct-bandgap semiconductor. It was known that by inserting a p-n junction into GaAs, infrared radiation was emitted. Researchers were also aware of gallium phosphide (GaP). GaP is an indirect-bandgap material that does not emit much light, but because its bandgap is larger, it has the potential to emit visible light. The question remained as to whether phosphorus could be added to GaAs to produce an efficient, direct-bandgap material that would emit light in the visible range. Scientists had speculated about this, and most thought that mixing such materials would only create an alloy with so many defects that it would emit little or no light at all. However, Holonyak was able to do it; he generated red LEDs and, in fact, made a red laser.”
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