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 degrees C, MOCVD 1050 degrees C and HVPE at 1050 degrees 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 degrees C by HVPE was recognized to be single crystalline, but buffer layers with mosaic-structure are formed at 1050 degrees C either by MOCVD or HVPE. High growth temperature of 1350 degrees 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 (similar to 1350 degrees C) have the lowest treading dislocation density similar to 3x10(8) cm(-2) determined using a combination of X-ray rocking curve measurement and plan-view transmission electron microscopy.