Defect reduction of super widegap semiconductor AlN by high temperature metalorganic vapor phase epitaxy and device applications

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Blue, green and white light emitting diodes and violet laser diodes on sapphire substrates have been already commercialized which are based on the low temperature buffer layer technology developed by us. Applications of nitride semiconductors are not limited to visible range, but can be applied to ultraviolet range. Expected applications of solid state UV/DUV light emitters/detectors include sterilizer, DNA analyzer, laser knife, flame sensor, dermatology, molecular tweezers, weather observation, gas decomposition, photolithography, etc. Formerly, AlN was grown at or lower than 1,200□ on other materials such as sapphire or SiC. Our previous mass transport study showed that in order to achieve sufficient migration of Al precursor, AlN should be grown higher than 1,200□.The objective of this study is as follows ;(1)Growth of AlN substrate by sublimation(2)Growth of AlN on sapphire by metalorganic vapor phase epitaxy (MOVPE) at high temperature, and(3)Fabrication of high quality AlGaN-based quantum structure and UV emitting deviceIn 2003, custom designed MOVPE reactor which is capable of raising temperature as high as 1,800□ was installed and operated with the cooperation of Ibiden Co.,Ltd. Sublimation growth of AlN on SiC and spontaneous nucleation was performed. In 2004, world's shortest wavelength laser diode on sapphire was successfully fabricated on epitaxially lateral overgrown (ELO) low dislocation density AlGaN. High quality and thick AlN was grown on sapphire by high temperature MOVPE. In 2005, we successfully grow low dislocation density AlN on sapphire using ELO technique with a dislocation density as low as 10^7cm^<-2> or less.