Hydride vapour phase homoepitaxial growth of GaN on MOCVD-grown 'templates'

We report on an improved quality of thick HVPE-GaN grown on MOCVD-GaN 'temp late' layers compared to the material grown directly on sapphire. The film- substrate interface revealed by cathodoluminescence measurements shows an a bsence of highly doped columnar structures which are typically present in t hick HVPE-GaN films grown directly on sapphire. This improved structure res ults in a reduction of two orders of magnitude of the free carrier concentr ation from Hall measurements. It was found that the structure, morphology, electrical and optical properties of homoepitaxial thick GaN layers grown b y HVPE were strongly influenced by the properties of the MOCVD-GaN 'templat e'. Additionally the effect of Si doping of the GaN buffer layers on the HV PE-GaN properties was analysed.