Crystalline qualities of three AlN films grown by cold-wallhigh temperature hydride vapor phase epitaxy (CW-HT-HVPE) on c-plane sapphire substrates, with different AlN buffer layers (BLs) deposited either by CW-HT-HVPE or by hot-wall low temperature hydride vapor phase epitaxy (HW-LT-HVPE), have been studied. The best film quality was obtained on a 500-nm-thick AlN BL grown by HW-LT-HVPE at 1000 degrees C. In this case, the AlN epilayer has the lowest full-width at half-maximum (FWHM) values of the (0002) and (10-12) x-ray rocking curve peaks of 295 and 306 aresec, respectively, corresponding to the screw and edge threading dislocation (TD) densities of 1.9x10(8) cm(-2) and 5.2x10(5) cm(-2). This improvement in crystal quality of the AlN film can be attributed to the high compressive-stress of BL grown by HW-LT-HVPE, which facilitate the inclination and annihilation of TDs.