Integrated Vertical LED Technology
20100222 - 20111222
Dr Francis Chee-Shuen Lee
• Deliverable 1 - Wafers (with sapphire removed): total 10 pieces The main purpose is to demonstrate the reproducibility and consistence of the processes. The 10 wafers should all show that the collateral removal of GaN during sapphire removal process is controllable by the addition of an etching process step with the help of etching stop layers. The GaN epitaxial layer thickness variation after sapphire removal should be within ± 3% of the total epitaxial layer thickness in 80% of the wafer area. (3% is about 0.15 micrometer if the epitaxial layer thickness is 5 micrometer.) • Deliverable 2 - LED prototypes: No. of packaged LEDs: 100, selected from 10 wafers, 10 LEDs from each wafer Chip Size: 1mm x 1mm (40 mils) Average light output power compared to standard LEDs (same wafer source, similar process conditions): (i) 20% higher at 350 mA (ii) 50% higher at 1500 mA DC Operation currents: 1A, 1.5A, 2A Forward voltage at 350 mA: < 3.5 V Reliability: light output power drop < 15% after 1000-hour operation at 2 x 350 mA (2 times the standard operation current).
Epistar [Sponsor] Epistar Co. The Hong Kong University of Science and Technology Walsin [Sponsor] Walsin Lihua Co. Ltd
The proposed R&D project aims to develop an integrated technology for the fabrication of power GaN LED chips, incorporating epitaxial layer structure design into the sapphire removal technology that has been developed by ASTRI. This integrated technology will improve process uniformity (thus production yield eventually) and LED chip performance. GaN LEDs generate light in different colors: green (G), blue (B), purple/violet, ultraviolet, and white. Current GaN LEDs use sapphire as the substrate. Sapphire is an insulator and not a good thermal conductor, fundamentally limiting the power capability of such LEDs. This bottleneck is eliminated by replacing sapphire with a new substrate by a novel technology developed by ASTRI. In this proposed project, this novel sapphire removal technology will be further advanced through design in the epitaxial structures of the wafer. We will work closely with Hong Kong universities and industry, as well as other companies in greater China area. There is no company in China (including Hong Kong) that is in mass production of power white LED chips, but many are racing to produce power LED chips. The technology to be developed in this project will be transferred to the industry to upgrade their technologies and reduce the cost and increase the throughput for power LEDs. While ASTRI’s LED Program is strong in LED applications, and has established devices team through the development of the sapphire removal technology development, this project will help ASTRI to strengthen the LED devices team, moving into upstream technology of epitaxial epitaxial layer structure, enhancing ASTRI’s overall LED technology strength.