The use of gallium nitride for solar power electronics and light emitting diodes (LED) holds a lot of promise, but the material is expensive and difficult to make. Here comes Soitec and Sumitomo Electric Industries, which announced Tuesday that they have completed their lab work on producing gallium nitride wafers and are moving into pilot production.
The two companies began the joint research and development work in December 2010 and initially were able to create 2-inch wafers. They have been able to scale up to 4-inch wafers and can even do a 6-inch version. The companies are now working on setting up pilot production lines in Japan (Sumitomo) and France (Soitec) to first produce 4-inch wafers. They plan to move to the 6-inch version later, depending on customer demand.
The use of gallium nitride is more common in LEDs. It also is being investigated by many developers of power conversion devices for solar and the electric grid, a large market in which silicon dominates as the material of choice for devices that adjust the current, voltage and other characteristics of electrical power. Google-backed Transphorm made its public debut last year to discuss its gallium nitride-based power conversion technology. The startup wants to see its devices in data centers, solar energy systems and electric cars.
Gallium nitride promises to deliver more efficient power conversion devices than silicon, which is reaching its limit in efficiencies. But gallium nitride isn’t found in nature, and making it so that it doesn’t degrade significantly and quickly is a big technical challenge. Making it cheaply is, of course, a good thing, especially if it is to replace silicon. Some LED makers, such as Osram Opto Semiconductors, have started moving from 4-inch to 6-inch wafers.
Many solar inverter makers are researching the use of gallium nitride, though some of them don’t anticipate launching products with this more exotic material soon. Enphase Energy is doing it, and it’s teaming up with Transphorm to work on gallium-nitride inverters.
Gallium-nitride has been more commonly grown on sapphire or more recently on silicon carbide substrate, and many companies are either working on producing larger wafers or new substrate materials, such as glass, to reduce manufacturing costs and improve performance.
The research work by Soitec and Sumitomo focuses on creating gallium-nitride substrates. Sumitomo has been working on gallium-nitride substrates for years now because making gallium-nitride devices on gallium-nitride substrates could produce better-performing devices such as the brighter, blue LEDs.
The pilot production plan calls for Sumitomo to produce gallium-nitride substrates and ship them to Soitec, where Soitec will use its process it calls “Smart Cut” to create the final wafers for sale. Soitec said its technology, which slices and transfers layers from one substrate to another to engineer better wafers, creates wafers with fewer defects.