The shape of sapphire wafer on the epitaxial growth of GaN layers

A sapphire wafer is the well-know substrate in the application of LED chips. As the size of wafer become lager, BOW and TTV of wafers can affect more to the growth of GaN epi-layer. The quality of the GaN epi-layers and optical properties on various shapes of 4″ and 6″ Al 2 O 3 (0001) wafers were investigated. 3 types of wafers were used in BOW ranges of ±10µm. In the experimental rages of BOW, structural quality of thin film and optical properties don't have significant difference.