a-plane GaN was grown directly on an r-plane sapphire (-0.45 degrees) substrate by low-pressure metalorganic vapor-phase epitaxy (LP-MOVPE), and the effects of the reactor pressure and growth temperature oil the crystalline quality and surface morphology of a-plane GaN were studied, The reactor pressure and growth temperature were adjusted from 40 Torr (53 hPa) to 500 Torr (666 hPa) and from 1020 to 1100 degrees C, respectively. a-plane GaN with a smooth surface morphology was obtained under low-pressure conditions, and high-crystalline-quality a-plane GaN was obtained at a pressure of 500 Torr (666 hPa). By controlling the reactor pressure and growth temperature, high-quality a-plane GaN with a smooth surface was obtained. (C) 2008 Published by Elsevier B.V.