Most of the microwave amplifiers modules (MMICs), mixers, etc. the company I work for are built on GaAs, and we're starting to use GaN (Gallium Nitride) on one of our Ka band units (28-31GHz). The GaN parts are quite a bit more power efficient.

Not exactly sure why the tech is not more widely used though. Funnily enough, most of the GaN and GaAs devices in general use are LEDs!

In late 1980s, it was expected that by 2000, you'd have a GaAs computer on every desktop (powered by Occam or Prolog, of course ;-)). In the end, it turned out that silicon had more life in it than was expected, while being much cheaper and easier to manufacture.

There was also the fact that silicon was already heavily entrenched in the industry by the time people started to tinker with the possibilities of GaAs seriously. At least that's what I understood to be the main factor after listening to Seymour Cray's talk which was posted here some time ago: https://www.youtube.com/watch?v=xW7j2ipE2Ck He talks about how difficult it was to convince large suppliers to work with GaAs at about 30 minutes into the talk.

Gallium-Arsenisde has a high switching speed because of the higher carrier mobility, but the higher frequency applications it is used in dissipate high power.

This article's transistors will not likely have a high switching speed, just high enough for switching power converters (100kHZ-few MHZ). The important feature of GaN according to the article is that you generate 1/10 the waste heat from current just flowing through the switch.

Power transistors don't perfectly 'turn on' like an ideal switch. They have a resistance to the switched path on the order of milliohms called Rds (resistance source to drain). And, heat dissipated from that is ~ I^2 x Rds.

Right but you can make your on resistance arbitrarily small by speccing a bigger transistor. It might cost more, but there's plenty of ability to reduce the on resistance.

My guess is that this is a breakthrough because it has lower resistance per unit of gate capacitance. It takes a certain amount of energy to switch the transistor on, and when you want to turn it off you generally connect it to ground so that the switch turns off very quickly. That energy is lost.

I've emailed a very experienced electronics engineer friend of mine who has built more switching power supplies than anyone I know. He hasn't gotten back to me yet.

It really has to be something more than the "on" resistance though. It's possible to get arbitrarily large MOSFETs and get micro-ohm resistance, where as the GaN transistor has milli-ohm resistance.

http://www.digikey.com/product-detail/en/TPHR9003NL,L1Q/TPHR...

http://www.gantechnology.com/products.html

Well Gallium-Arsenide, Indium-Phosphide and all kinds of other semi-conductors. But thing is, Silicon is well entrenched and there are work-arounds for all the different shortcomings of silicone and really a lot of experience working with Si. So the theoretical advantage of different substances where never able to overcome the momentum Si has.

They will eventually, working from the extreme cases on in as price drops, but for the foreseeable future, Si is king.