Ever wondered what's inside a LED?

Gone are the days when LEDs were just used as replacements for dial lamps and indicators.

I remember (probably back in the early ’70s) when a then-much-younger Dick Smith used to advertise what was a pretty pedestrian multi-band radio receiver with, wait for it, a "LED Lamp Indicator" which moved up and down the dial as you tuned it. Wow! (Of course he sold thousands!).

That was only about a decade after LEDs were first commercially produced. Even then, they were still relatively expensive and were rather dim by today’s standards. LEDs have certainly come a long way, even in those thirty-ish years. But let’s go back even further and have a look at where LEDs came from.