GaN layers of thickness 0.5-1.3 mm were grown at 1280 degrees C at a growth rate of 95-275 [mu m/h by tri-halide vapor-phase epitaxy on nonpolar m-plane (10 (1) over bar0) and semipolar (10 (1) over bar(1) over bar) ammonothermal GaN substrates. For nonpolar m-plane (10 (1) over bar0) with a -5 degrees off -angle, the full widths at half maximum (FWHMs) of X-ray rocking curves (XRCs) and the basal plane stacking fault (BSF) density increased from 50 to 178" and from 4.8x10(1) to 1.0x10(3) cm(-1), respectively, upon increasing the growth rate from 115 to 245 mu m/h. On the other hand, the XRC-FWHM and the BSF density for semipolar (10 (1) over bar(1) over bar) grown at 275 mu m/h were as small as 28" and 8.3x10(1) cm(-1), respectively.