Our first exhibit: An example of technology used in the very first Light Emitting Diode ever mass-produced for industry and consumer.|
First appearing around 1969, this technology was actually available as early as 1962 but at that time only as a rather expensive and rare laboratory curiosity. Early models came in tiny metal cans with a clear window, bubble, or lens on the end. This model is obviously newer.
This breakthrough model emitted infrared light, which is essentially invisible to the human eye. Fortunately for us, a variety of technology exists today which can capture this invisible light for old time's sake. Shown under the LED is one way of doing that: a chemically doped card that converts infrared into an orangish glow us humans can see. Video & digital cameras are also usually sensitive to this kind of invisible light.
Chemically, this LED consists of the compound Gallium Arsenide; which is the metal gallium and the element arsenic, familiar to some of you as an older type of mouse & rat poison. Put two and two together, and you have the world's first completely solid-state, cold light source. Thus, the LED was born.
This is how the LED would look to you if you could see infrared light. Here, the camera, sensitive to the 950nm wavelength, shows you the rather unusual double-whisker design of this early LED.
An LED like this was probably first used in factory machinery for object detection; an upgraded version of this LED eases our daily lives, living in our TV and VCR remote control units and as sensors in all kinds of products we use every day.
Arguably, this is likely one of the first visible red LEDs to surface.|
Appearing around mid 1969, this Monsanto MV2 red LED was purchased in London at a military surplus store on Tottenham Court Road. It originally cost £1, at a time the typical wage earner made £7 a week. So it was not cheap.
As you can see by the picture, this came in a metal can with a glass or acrylic bubble on the business end.
This LED has a very unusual chip construction, consisting of a gallium arsenide substrate (the base material) with a gallium arsenide phosphide emitting layer, and has a metal contact ring serving as the 1960s counterpart to today's gold bond ball.
The actual light emitting surface is a circular region inside this ring, as shown in the picture. A small amount of red light also emenates from the vertical surfaces of the chip substrate; this is splotchy and irregular and is probably some GaAsP "overspray" of sorts from what was then a crude (by today's standards) manual manufacturing process.
Chemically, this LED consists of the compound GaAsP on a GaAs substrate. When unlit, the color of the chip is a jet black. The anode ring is probably platinum, rhodium, or other nonreactive rare earth metal; and the rest of the metal components inside the LED are gold plated.
Thanks to David Chambers in Scotland for hanging on to this LED for thirty plus years.