In this study, the properties of Al0.18Ga0.82N films grown on stripe-grooved GaN templates with different trench depths have been investigated by field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), double crystal X-ray diffractometer (DCXRD), and photoluminescence (PL) measurement. Based upon the results of FESEM observations, a crack-free Al0.18Ga0.82N surface has been achieved using a GaN template with 1-mu m-deep trenches. Moreover, from the observations of TEM, the density of threading dislocations in Al0.18Ga0.82N film was found to reduce during the lateral growth on the trench regions. DCXRD and PL both measurements were carried out to determine the quality of the Al0.18Ga0.82N films. The full-width at half-maxima of double crystal X-ray rocking curve and PL spectrum are the smallest, respectively, for the Al0.18Ga0.82N film grown on grooved GaN template having 1 mu m-deep trenches. It is believed that the use of the grooved GaN templates effectively improves the quality of the overgrown Al0.18Ga0.82N films. (c) 2006 Elsevier B.V. All rights reserved.