An Fe-doped thick GaN layer was grown by hydride vapor-phase epitaxy on a (111)A GaAs starting substrate. By removing the GaAs substrate, a 400-mu m-thick (0001) GaN substrate having a smooth surface and an Fe concentration of 1.5 x 10(19) cm(-3) was obtained. X-ray diffraction rocking curves of the (0002) and (10 (1) over bar0) planes of the GaN substrate had narrow full-widths at half-maximum of 410 and 360 arcsec, respectively. The etch-pit density of the GaN substrate was 8 x 10(6) cm(-2). Extended X-ray absorption fine structure analysis revealed that the Fe atoms are substituting for the Ga in the GaN. The GaN substrate had a high resistivity of 8.8 x 10(12) Omega cm at room temperature. (c) 2006 Elsevier B.V. All rights reserved.