Admit it -- you weren't thinking about it over breakfast. But it will could well have a major impact on your career.
Epitaxial growth is the process of growing monocrystalline films on top of a monocrystalline substrate. In homoepitaxy, the layers consist of the crystals of the same elements; in the sometimes more challenging heteroepitaxy, different crystalline substances ultimately get fused together in a microscopic version of sedimentary rock.
The key -- and a major reason that it will continue to rise in importance -- is that epitaxial processes require finesse and a company that can harness them cleverly can develop differentiated products.
"It’s somewhat of an art. You can’t make decent stuff without epitaxial active layers,” Aldo Kamper, president and CEO of Osram Opto Semiconductor told us earlier this month in an interview. “Every machine has its own identity. You need R&D."
Kamper further added that the challenges surrounding epitaxial growth and the relatively limited number of engineers well versed in the subject were two of the reasons China makers may have a tougher time catching up to established players in lighting than they did in solar. “There is still a technology gap and a large quality gap,” Kamper added. “It is not so easy to catch up.”
Some of other recent epi news:
--Bridgelux this week said it has come up with a way to grow gallium nitride crystals on top of inexpensive crystalline silicon wafers to make LEDs, a long sought goal. Now, LED manufacturers require expensive silicon carbide or sapphire wafers. The process could lower the price of a single LED chip from 30 cents to 45 cents now to 5 cents or less in the future. Mass production could start in two to three years.
The breakthrough revolves in part around inserting thin films between the silicon and gallium nitride layers. Epitaxial growth of crystals requires high temperatures and the different cooling/heating rates of silicon and gallium nitride generally causes cracking. (That's an epi reactor in the photo.)
--Alta Devices, a stealthy startup based on research out of Caltech and UC Berkeley, just raised a $72 million round. Alta hopes to produce solar modules that are 30 percent efficient and cost less than 50 cents a watt. Now, the most efficient crystalline silicon solar cells on the market only hit about 23 percent efficiency and the cheaper (and less efficient) solar modules cost around $1.00 to 75 cents a watt to produce.
The company's technology involves "epitaxial lift-off," which sounds like a way to use crystalline structures to make wafers. Wafer processing is incredibly inefficient: in solar manufacturing, nearly half of the silicon from an ingot becomes dust and waste that needs to be recycled. Alta's material of choice is gallium arsenide.
--1366 Technologies is trying to perfect a process for producing wafers for crystalline silicon solar cells. The goal is to lower to cost of making wafers to around 25 cents a watt. Now, wafers cost around 72 cents a watt to make. A 25-cent wafer will lead to solar power -- including installation, electronics, and the module -- for $1 per watt, says CEO Frank van Mierlo.
While van Mierlo declined to tell us much about the process, he said to think of how one might peel layers of ice off of a frozen lake. Sounds like what Alta is describing.
--A whole slew of wafer companies -- Crystal Solar, Ampulse, AstroWatt, Bangap Engineering, Twin Creeks Technologies -- for solar have emerged that in some way or another differentiate themselves through crystalline growth.
--Transphorm recently came out with a fairly remarkable way to make AC to DC converters with gallium nitride. See above.
So there you have it. In fact, the stress on epi this month underscores another big megatrend in green -- material science can be classified as one of the six fundamental disciplines of the industry.
In nearly every sub-segment of green you can find some of primary advances coming through materials. Concentrators may finally come to the solar market because of cheaper materials from companies like 3M, while startups and conglomerates alike are tinkering with lightweight materials for wind turbines. In cars, weight is the third fuel: Bright Automotive wants to exploit new body materials to increase mileage by shedding pounds.
This is either a pattern, or I went off the deep end.
The other five disciplines are: electronics (microinverters, DC maximizers, building control systems, transformers), behavioral science (Opower, CityBin, EcoFactor, solar leasing), biology (Solazyme, Genomatica, Sapphire Energy, Codexis, Amyris) mechanical/systems engineering (BrightSource Energy, Lehigh Technologies), and chemistry (Ostara Nutrient Recovery Systems, Zeachem). More on the six disciplines in a future article.