🚀 go-pugleaf

In article <1991Jan16.034246.12843@zoo.toronto.edu> wern@zoo.toronto.edu (Wern Thiel) writes:
>Does anyone have comprehensive references as to who invented/developed the
>LED? While many components (transistor and IC's) are covered in books and
>texts; the LED seems to be missing. It would be interesting to read about
>the research that led to the LED. Similar situation regarding liquid
>crystal technology. We got our first LED in about 1974 for $10.

I found an article by Forrest M. Mims, III in an old Popular Electronics.
Because it may be difficult for some to find I have posted much of it here.

Mr. Mims has columns in Modern Electronics and Scientific American.
Perhaps he could write an updated article?


Light-emitting Diodes
by Forrest M. Mims, III
Popular Electronics
November, 1970 p 35

One of the least known but most fascinating of semiconductor devices is
the light-emitting diode (LED). Until quite recently, these devices were
too expensive for widespread use; however, technological advances in their
fabrication now make possible moderately low prices so that they are
attractive to the electronics experimenter.

The first recorded instance of light being generated by a "diode" was in
1907 when H. J. Round touched a pair of battery wires to a crystal of
silicon carbide. Much to his surprise, flashes of yellow light were
emitted at the contact region of one of the battery wires -- he had
accidentally discovered the LED. Unfortunately, his discovery was
forgotten and not until the early 1950's did scientists once again study
semiconductor light emission. At that time several patents were applied
for covering LED's made from silicon or germanium -- common semiconductor
materials. One of these patents not only described the principle of the
LED but listed several fascinating uses for the device. Among them were
light-beam communication systems, light "radar", and light-beam
alignment devices.

Unlike the 1907 silicon carbide cat whisker diode, the 1950's LED's
emitted infrared light (see Fig. 1) [ not included, dmt ]. The invisible
beam was desirable but researchers began a concentrated effort to
fabricate LED's in the visible range. The first company to market any
kind of LED was Texas Instruments, Inc. Their diodes included infrared
emitters made from gallium arsenide (GaAs) and visible emitters made
from gallium arsenide phosphide (GaAsP). These diodes were expensive;
but their appearance on the commercial market in 1962 whetted the
appetites of design engineers -- and of course was of great interest
to other semiconductor manufacturers. While scientists at IBM and Bell
Telephone performed basic research on the devices (especially visible
emitters), General Electric, Monsanto, Electro-Nuclear Laboratories
and others began competing with TI.

Since the LED has an almost unlimited lifetime and because of its low
operating current, many claims were made for its potential in flat
screen television, indicator lamps, night lights, and even as a
source of room lighting. The extremely fast modulation capability of
the LED made possible several demonstrations of voice communications
permitting two parties to converse over a beam of invisible infrared
light for clear weather distances of several miles.

...
An important result of all these new uses for LED's is a large drop in
price. LED's are available for under $2.50 each in small quantities.
This price is competitive with that of miniature, long-life indicator
lamps. And of course, the LED offers sturdier packaging, a million-hour
lifetime, and far less current consumption.

Only a year ago, the cheapest infrared LED retailed for $18.00. At least
five manufacturers now offer GaAs LED's for under $7.50.
...

GaAs diodes are so efficient as light emitters that scientists chose them
as candidates for early work concerning the feasibility of fabricating
semiconductor lasers. In the fall of 1962, researchers at G.E., IBM,
and MIT announced almost simultaneously lasers made from specially
prepared GaAs diodes.
-- 
Dave Turner	415/823-2001	{att,bellcore,sun,ames,decwrl}!pacbell!dmturne