Crack formation in GaN on Si(111) substrates grown by MOCVD using HT Al-preseeding and HT AlN buffer layers

We have investigated the crack formation in GaN layers grown on Si(111) substrates by MOCVD using an AlN buffer layers and Al-preseeding process. With an appropriate AlN buffer thickness using optimal TMAl flow rate, we were able to counteract the crack formation usually observed in GaN layers deposited on Si(111) substrate. With a 120 nm thick AlN buffer layer, TMAl source flow rate 18 mu mol/min and Al-preseeding time 5 s, we were able to obtain nearly crack free 2.5 mu m GaN surface and a (002) plane HR-XRD rocking curve FWHM of 385 arcsec is achieved. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim