SEI edges closer to commercial GaN
The company has started shipping samples and is presently working to mass-produce the substrates for the so-called Blu-ray Disc optical video recording technology.
The new substrate has regions of low dislocation densities that are about 500 µm in diameter. The dislocation densities in these regions range from 10,000 to 100,000, which is 100,000 times less than the dislocation density of conventional GaN epitaxial layers on sapphire substrates.
SEI developed the world s first 2-inch GaN wafer two years ago using a unique GaN substrate fabrication process, called the "dislocation elimination by epitaxial growth with inverse-pyramidal pits" (DEEP) technique.
This technique reduced dislocations by forming inverse-pyramidal pits on the surface of the crystal. But even with DEEP, the low dislocation areas in SEI s substrates were too small to be useful in the next stage of wafer fabrication.
However SEI has developed a technique that not only controls the regions where dislocations are concentrated, but also extends the low-dislocation density areas. As a result the latest substrates contain low dislocation regions that are 500 µm in diameter and ordered, which SEI says makes device fabrication easier.
The new substrate also features higher conductivity and offers better cleavage, which makes it more efficient for use in laser devices.
SEI plans to mass-produce the substrates once laser device manufacturers have evaluated the new GaN substrate. The company expects to fabricate 300 substrates per month by April 2003.
