Seren Photonics Ltd of Pencoed Technology Park, UK (which was spun off from the University of Sheffield in February 2010) has launched its next generation of semi-polar gallium nitide (GaN) on sapphire templates. This latest generation of 11-22 GaN templates continues to be based on Seren's patented approach developed by professor Tao Wang's team at the University of Sheffield.
The improved performance comes about through a manufacturing upgrade that not only improves crystal quality, but also enhances manufacturing yield. This approach has already completed qualification for a 2"-diameter product and, as part of its development activity, Seren has now adapted the enhanced approach to the development of 4" and 6" templates.
"With demand for 4" and 6" accounting for over 75% of the sapphire market for LEDs, the need to provide customers with industry-standard 4" diameter wafers along with the option to upgrade to 6" makes total commercial sense," says chief development officer Bedwyr Humphreys. The 4" templates for customer sampling are expected during third-quarter 2015, with 6" planned to come online during first-half 2016.
Semi-polar GaN displays anisotropic behaviour under x-ray diffraction. So, unlike c-plane GaN, the crystal quality is dependent on the direction along the wafer that the measurement is taken. This latest development has overcome this issue, says Seren, yielding a semi-polar GaN layer with isotropic crystal quality. This not only enhances the optical isotropy of the material but also ensures that electrical properties such as mobility are also isotropic.
The latest generation of Seren's of semi-polar GaN-on-sapphire templates is now available for sampling in 2" diameter or custom sizes. At less than 5um thick, the GaN layer for these semi-polar templates is the thinnest available on the market, the firm claims, ensuring minimal wafer bow with maximum defect blocking.
