Microstructure and influence of buffer layer on threading dislocations in (0 0 0 1) AlN/sapphire grown by hydride vapor phase epitaxy

Abstract

The microstructures of AlN films grown by high-temperature hydride vapor phase epitaxy (HT-HVPE) on (0 0 0 1) sapphires with three different kind of buffer layers (BLs) were investigated by plan-view and cross-sectional transmission electron microscopy (TEM). The buffer layers were grown by HVPE at 1350 °C, MOCVD 1050 °C and HVPE at 1050 °C. The microstructures and in-plane misorientation of buffer layers are related to the crystal quality of the AlN films and dislocation evolution. The misorientation angles and average grain sizes of buffer layers were analyzed quantitatively using Moire fringe method. The buffer layer grown at 1350 °C by HVPE was recognized to be single crystalline, but buffer layers with mosaic-structure are formed at 1050 °C either by MOCVD or HVPE. High growth temperature of 1350 °C significantly reduced the in-plane misorientation of the buffer layer and the dislocation density was greatly reduced. AlN films on high-temperature growth buffer layers (∼1350 °C) have the lowest treading dislocation density ∼3 × 108 cm−2 determined using a combination of X-ray rocking curve measurement and plan-view transmission electron microscopy.