Eta research of Lingang free trade zone, Shanghai, China, which was founded in 2015 to develop free-standing gallium nitride (GaN) wafers, is now selling n-type 100mm GaN wafers with an epitaxial-ready polish.
Eta has completed the R&D necessary to commercialize GaN wafers, resulting in its unique hydride vapor phase epitaxy (HVPE) equipment, wafer separation process, and polishing process. In 2018, the firm demonstrated as-grown GaN wafers of 100mm diameter that can be cut to 2” and 3” wafers as the finished size. This year it developed almost 5” as-grown GaN wafers that can be cut and processed into 100mm wafers.
Eta says that it places a strong emphasis on the importance of the crystal quality and lattice curvature. The typical rocking curve full-width half-maximum (FWHM) of the as-grown wafers is 50-60 arcsec for both the (002) and (102) reflections. The threading dislocation density has been measured as 1E6/cm2 based on the cathodo-luminescence (CL) of polished wafers. The lattice curvature is important as a measure of the offcut variation across the wafer. The center point offcut is specified at 0.35° toward the GaN m-direction, and that can be modified according to the customer’s requirement. The lattice curvature radius is greater than 10m, with the target around 30m or larger.
The firm has developed its own polishing process for GaN, resulting in atomic force microscope (AFM) average roughness over 10μm images of <0.3nm. It has grown MOCVD GaN epilayers and device structures on the GaN wafers. The MOCVD-grown layers are said to show good surface morphology and have x-ray diffraction (XRD) rocking curve FWHMs similar to that of the substrate.
Currently, small quantities of 100mm GaN wafers are for sale, as well as 2” and 3” wafers. At the end of 2019, more HVPE capacity will be brought online in the new production factory located in Tongling, Anhui Province, China. The firm expects to be able to supply high-volume customers in the near future. Further, working with their epitaxial growth partners, Eta can offer GaN wafers with MOCVD epilayers for interested customers.