Azzuro's "one-bin" wafer prototype was demonstrated at the 10th International Conference on Nitride Semiconductors (ICN-10) in Washington, DC. After questions about achieving competitive brightness and efficiency levels have been answered by various GaN-on-Si contenders, the yield question has remained open in LED manufacturing. The large mismatch of crystal lattice structure and thermal expansion coefficient cause highly bowed LED wafers after and during growth. This in turn has a very big negative impact on uniformity levels for wavelength, forward voltage and output power. Azzurro uses its proprietary strain-engineering and growth technologies to overcome these obstacles.
The company has showed wafers with uniformity from production for wavelength (< 3 nm or 0.6%), forward voltage (1.3%) and output power (3.9%) for highly reduced binning. At the same time, the Azzuro engineers achieved remarkable values for 200 mm LED wafers. Manufacturability parameters such as low bow (< 20 μm) and very good thickness uniformities (1.7%) are not compromised on, the company's experts claim. Based on these achievements the technical team continues to push for the ultimate “one bin” wafer aim and demonstrated the benchmark result for wavelength with only 1.0 nm uniformity and a min/max value of 5 nm (one wavelength bin).
Azzurro believes that these results from production and development prove that in addition to the cost advantages from lower cost substrates and by using standard silicon fabs for LED chip processing GaN- on-Si LED wafers with the right strain-engineering technology can help reduce binning dramatically.