In a presentation at the 10th International Conference on Nitride Semiconductors (ICNS-10) in Washington DC, USA (26-28 August), AZZURRO LED Technologies of Dresden, Germany announced that it has demonstrated '1-bin' wavelength LED wafers. While showing production values of less than 3nm wavelength uniformity, the 1.0nm result came straight from development. The firm says that the record 1.0nm result demonstrates the capability to achieve '1 bin' gallium nitride on silicon (GaN-on-Si) LED wafers with AZZURRO's technology.
Formed in July to enable the LED industry's migration to GaN-on-Si, AZZURRO LED Technologies is a business unit of AZZURRO Semiconductors AG of Dresden, Germany, which makes GaN epitaxial wafers based on large-area silicon substrates for both LED and power semiconductor applications.
AZZURRO says that, after questions about achieving competitive brightness and efficiency levels have been answered by various GaN-on-Si contenders, the yield question has remained open. The large mismatches in both crystal lattice structure and thermal expansion coefficient between GaN and silicon cause a high degree of bowing in LED wafers during and after growth. This in turn has large negative impact on uniformity levels for wavelength, forward voltage and output power. AZZURRO uses its proprietary and patented strain-engineering and growth technologies to overcome these obstacles.
What is claimed to be breakthrough uniformity from production for wavelength (<3nm or 0.6%), forward voltage (1.3%) and output power (3.9%) for highly reduced binning were presented at ICNS-10, together with what is reckoned to be excellent crystal quality values for 150mm-diameter blue-emission GaN-on-Si LED wafers (where all values are standard deviation). At the same time, what AZZURRO describes as equally impressive values for 200mm LED wafers show the technology's scalability. Manufacturability parameters such as low bow (<20μm) and good thickness uniformities (1.7%) are not compromised, notes AZZURRO.
Picture: Wafer uniformity map, showing 1.0nm (0.2%) standard deviation.
The firm says that, based on these achievements, its technical team continues to push for the ultimate '1 bin' wafer as a target, and hence demonstrated the benchmark result for wavelength with 1.0nm (0.2%) uniformity and a minimum/maximum value of 5nm (one wavelength bin).
AZZURRO says that the latest results from production and R&D show that - in addition to the cost advantages from lower-cost substrates and using standard silicon fabs for LED chip processing - GaN-on-Si LED wafers with the right strain-engineering technology can also help to reduce binning dramatically.
"With these results we show that our GaN-on-Si technology can bring the LED industry closer to the aim of making '1 bin' LED wafers," comments AZZURRO's co-founder & CMO Alexander Loesing, who also heads the LED Technologies business unit.
