| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2006: ¥1,100,000 (Direct Cost: ¥1,100,000)
Fiscal Year 2005: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
In this study, we suggested CrN as a new buffer layer for GaN and A1GaN. Cubic structured CrN (111) film has smaller lattice mismatch with sapphire substrate (6.6 %) than that of GaN film. Moreover, CrN film has intermediate thermal expansion coefficient (6x10^<-6> /K) between sapphire substrate (6.66x10^<-6> /K), and GaN film (5.59x10^<-6> /K).Also, CrN, nitride material, which has nearly same physical properties with GaN an A1GaN is very stable in high temperature. In the first attempt, the two-step growth with the combination of MBE (Molecula Beam epitaxy) and HVPE (Hydride Vapor Phase epitaxy) was used and the GaN was grown on CrN buffer layer. We could obtain the high quality GaN template substrate without cracks and bending. To evaluate crystallinity and surface morphology, we used four kinds of samples, MBE-grown CrN, MBE-grown GaN/CrN, low temperature GaN and metal organic chemical vapor deposition (MOCVD)-grown GaN template. GaN were grown on these samples by HVPE method. Thic
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k GaN films are grown on various templates on c-sapphire substrates, which include molecular beam epitaxy (MBE)-grown low temperature (LT) GaN, MBE-grown LT CrN, high temperature (HT) GaN/CrN buffer layer and metal organic chemical vapour deposition (MOCVD)-grown GaN, using hydride vapour phase epitaxy (HVPE). The HVPE-grown thick GaN on GaN/CrN buffer have no cracks at 401.tm film thickness and FWHM of (0002) wscan is 497 arcsec. These results indicate the feasibility of a CrN buffer applied to free standing (FS) GaN substrates. The Cr metal buffer layers were deposited on c-plane sapphire substrate as another method of CrN formation by sputtering. Nitridation of Cr metal layer, growth of GaN buffer layer and fmally high temperature GaN main growth was successively accomplished in HVPE reactor. High quality GaN epitaxial films were successfully grown on c-sapphire substrate with Cr metal buffer layer by HVPE. The GaN film grown on Cr metal buffer under optimized growth conditions showed mirror like surfaces, good crystalline qualities, and fine optical properties as compare with HVPE GaN grown on MOCVD GaN template. Less
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