Page 54 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

Semicondcrcfovs: Diodes and Tramistors II 35

much experimentation and refinement, the first red LEDs started to hit the
streets in the late 1960s.
LEDs are interesting for a number of reasons, not the least of which is that
they are extremely reliable, they have a very long life (typically 100,000 hours
as compared to 1,000 hours for an incandescent light bulb), they generate very
pure, saturated colors, and they are extremely energy efficient (LEDs use up to
90% less energy than an equivalent incandescent bulb).

Over time, more materials were discovered that could generate different
colors. For example, gallium phosphide gives green light, and aluminum indium
gallium phosphite can be used to generate yellow and orange light. For a long
time, the only color missing was blue. This was important because blue light
has the shortest wavelength of visible light, and engineers realized that if they
could build a blue laser diode, they could quadruple the amount of data that
could be stored on, and read from, a CD-ROM or DVD.

owever, although semiconductor companies spent hundreds of millions of
dollars desperately trying to create a blue LED, the little rapscallion remained
elusive for more than three decades. In fact, it wasn’t until 1996 that the
Japanese Electrical Engineer Shuj i Nakamura demonstrated a blue LED based
on gallium nitride. Quite apart from its data storage applications, this discovery
also makes it possible to combine the output from a blue LED with its red and
green cousins to generate white light. Many observers believe that this may
ultimately relegate the incandescent light bulb to the museum shelf.