RE: RE: RE: LED: Gallium on Gallium (no sapphire) The GaN to GaN technology is nascent at this point. It will not replace nor compete with sapphire for maintsream applications--except for specialty boutique uses, where extreme power/density/ brightness are required.
The latest contender for sapphire is silicon, where very large diameter wafers and technological breakthroughs have started to show promise [see article in Bloomberg below]
https://www.businessweek.com/articles/2012-11-29/bill-watkinss-at-no-and-bright-idea
The sapphire players, on the other hand, are hitting back with larger wafers [ from 2" to 6" and even 8"] helping to drastically cut down on cost. [see articles below]
https://ledsmagazine.com/news/8/10/32
https://www.businesswire.com/news/home/20130128005104/en/Rubicon-Technology-Ships-400000th-Large-Diameter-Sapphire
I see silicon LED's going after the upper niches of the mainstream markets, but will need to first muscle its way into the giant, well established players with plenty of incentive to compete on price, volume and technological refinements.