50 years ago: How Holonyak won the race to invent visible LEDs
- PDF / 735,319 Bytes
- 4 Pages / 585 x 783 pts Page_size
- 63 Downloads / 155 Views
MATERIALS HISTORY
50 years ago: How Holonyak won the race to invent visible LEDs Tim Palucka
T
he infinitely variable, precisely controlled riot of color that is New York’s Times Square is created by a vast array of light-emitting diodes, or LEDs. Certainly this glaring display of multicolored advertising was not what Nick Holonyak Jr., then the lead scientist of General Electric’s Advanced Semiconductor Laboratory in Syracuse, had in mind on October 9, 1962, when he demonstrated the first “visible” LED—a red glow from a small semiconductor crystal in an electronic circuit. But he knew his tiny device, which produced coherent red light and was thus a laser as well as an LED, would become important. In an article about lasers entitled “Light of Hope—or Terror?” in the February 1963 Reader’s Digest, Harland Manchester wrote of Holonyak’s invention: The latest dramatic laser discovery, made by General Electric, may someday make the electric light bulb obsolete. While the radiation from previous lasers was invisible, this one emits visible light in the red region of the spectrum. Research is continuing, and GE engineers hope to build lasers which will convert ordinary electric current into white light with a high degree of efficiency. “We believe there is a strong possibility of developing the laser as a practical light source,” Holonyak said in the 1963 article. “Much more experimental work must be done, and it might be ten years or more before such a lamp could be ready for wide use.” Within months of the invention, General Electric was selling Holonyak’s red LEDs, which produced diffuse, incoherent light—that is, light whose waves were not aligned in phase—for $260
each. These small, glass-encapsulated cylinders, sprouting two wires that looked like legs, contained the galliumarsenide-phosphide (GaAsP) crystal that produced the light. The laser version of the same material, which emitted an intense, narrow beam of red light due to the perfect alignment, or coherence, of its waves, was arbitrarily valued at 10 times the price of the LED, or $2,600. Soon, red LEDs were appearing as indicators on computers and in the sevensegment displays used to form numbers in digital alarm clocks. In the 50 years since then, LEDs have been produced in a wide range of colors for use in traffic lights, architectural lighting, backlights for liquid-crystal display (LCD) television screens, and large displays, such as those in Times Square. Recent advances in high-intensity, high-efficiency white LEDs have made them useful as street lights and conventional indoor lamps. Though it took longer than the 10 years
that Holonyak had predicted in 1963, white LEDS are now poised to replace Edison’s incandescent bulb, as well as fluorescent lamps. ***** LEDs owe their existence to two other inventions: the transistor and the ruby rod laser. The transistor, as is well known, was invented in 1947 by John Bardeen, Walter Brattain, and William Shockley at Bell Laboratories in New Jersey. The semiconductor sandwich that comprises the transistor
Data Loading...
