IMEC, Aixtron make GaN progress
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IMEC and Aixtron have demonstrated the growth of uniform AlGaN/GaN heterostructures on 200mm (111) silicon wafers. This demonstration, say the partners, is a milestone on the road to fabricating low cost GaN power devices for high efficiency, high power systems that are currently beyond the capabilities of silicon.
Marianne Germain, manager of IMEC's Efficient Power program, said: “There is a strong demand for GaN based solid state switching devices in the field of power conversion. However, bringing GaN devices to a level acceptable for most applications requires a drastic reduction in the cost of this technology. And that is only possible by processing on large diameter Si wafers. We aim to further develop the growth process and to qualify the wafers to be compatible with silicon cmos process.”
GaN, which extends the application field of solid state devices, has previously been grown on sapphire and silicon carbide substrates. However, silicon substrates are an attractive option; not only are they cheaper, they also have better thermal conductivity and are readily available.
200mm Si wafers with a (111) surface orientation have been custom made by MEMC Electronic Materials using the Czochralski growth method. This makes wafers suitable for switching applications with large breakdown voltages.
An AlN layer was deposited onto the Si substrate, followed by an AlGaN buffer which provides compressive stress in the 1µm thick GaN top layer. The stack was finished with a 20nm AlGaN (26% Al) layer and capped with 2nm of GaN.
