re blue led s in article c yqde cq ecf toronto edu gladman ecf toronto edu gladman aviv writes in order to emit blue light a semiconductor must have a band gap energy within the region of to electron volts according to my physical electronics prof you can t get an led with that band gap that s why you don t find blue leds or for that matter some other colour of leds that is not to say that blue leds can t be found i ve seen blue leds sold but they were just your typical visible light led in a blue plastic covering they didn t emit very much light um your professor if just plain wrong although blue leds are one heck of a lot less efficient than red ones typical visible light leds don t really exist leds have a fairly narrow region of transmittence since the fermi energy around either side of the band gap falls off exponentially blah blah source solid state electronic devices ben g streetman d ed prentice hall you might want to check the copyright date on that blue leds most certainly do exist i ve got a bunch at work cree research makes them probably along with other companies cree is big in materials science though they advertise in the stuff like physics today etc you can buy them from jameco i think digikey definitely and plenty of other distributors actually these days you can get a typical visible light led it s called a rainbow led and i ve forgotten who makes it they advertise in edn and many of the other trade rags though it combines a reg green and blue led all on one chip and has four leads nifty device although it s probably fairly expensive joel kolstad
