A collaboration between AIXTRON and Semileds has resulted in the successful fabrication of GaN-based blue LED chips on 6-inch sapphire wafers. Not only were optical results encouraging but also the process is sufficiently close to production compatibility that the company should soon be able to reap the rewards from larger wafers.
The 6-inch sapphire wafer process is based on MOCVD and a series of follow-on device fabrication steps through to final test. Specifically, the LED structure was deposited on a 1000 µm thick 6-inch sapphire substrate using an AIX 2800G4 HT MOCVD reactor in the 6x6-inch configuration.
Dr. Chuong Tran, President and COO of Semileds, comments on the results: “Brightness and efficiency are encouraging even though we are only a small step away from our existing and mature 4-inch sapphire process. Judging from the uniformity of the 18,000 1x1 mm Vertical LED on Metal Alloy chips from one single wafer, we can clearly see the yield advantage of this larger wafer MOCVD process. One of the contributing factors to yield enhancement is the significantly reduced edge area compared to the area equivalent of nine 2-inch wafers.”
Dr. Christian Geng, General Manager Greater China of AIXTRON adds: “The process obviously works from A to Z. I expect that once the price of a 6-inch substrate becomes competitive many of our customers will convert their AIX 2800G4 HT systems from 42x2-inch to 6x6-inch configuration since it merely requires the exchange of the so-called Satellite Disks.”