Unintentionally doped GaN with conventional single low-temperature (LT) AlN buffer layer and with double MgxNy/AlN buffer layers both were prepared. It was found that we could reduce defect density and thus improve crystal quality of the GaN by using double MgxNy/AlN buffer layers. GaN with double MgxNy/AlN buffer layers reveals an asymmetrical reflection (10 2) and (0 0 2) with a smaller full-width at half-maximum (FWHM), and a higher mobility, lower background concentration and lower etching pit density (EPD) than the GaN with the LT-AlN buffer layer. (C) 2008 Elsevier B.V. All rights reserved.