Migration enhanced MOCVD (MEMOCVD^TM) buffers for increased carrier lifetime in GaN and AlGaN epilayers on sapphire and SiC substrate

We report on using Migration Enhanced Metal Organic Chemical Vapor Deposition (MEMOCVD^TM) buffers for increasing lifetime of non-equilibrium carriers in GaN and AlGaN players grown on sapphire and SiC substrates. Photoluminescence (PL) and the light-induced grating technique (LITG) were used for the comparative study of the GaN and AlGaN epilayers with the MEMOCVD^TM multilayered buffers and with conventional buffers. Measurements on GaN layers grown on sapphire and SiC show carrier lifetime more than 300 ps respectively with MEMOCVD buffer layers which is more than 4 times higher compared to the layers on conventional MOCVD buffers. In the AlGaN layers, PL intensity increases for MEMOCVD buffer layer compared to conventional MOCVD layers possibly due to reduction in defect density. The LITG results also show higher carrier lifetime for Al_0.23Ga_0.77N (more than 190ps) with MEMOCVD AlN buffers compared to layers with conventional buffer layers. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)