High-resolution x-ray diffraction studies of highly curved GaN layers prepared by hydride vapor phase epitaxy

Abstract

In addition to dislocations, the wafer curvature can also affect the broadening of x-ray rocking curve (XRC) peaks and it may deteriorate the accuracy of the tilt and twist angle measurements. In this paper, the radial-distribution of curvature and the effects of wafer curvature on XRC of highly curved (the radius curvature of r less than 2.5 m) GaN layers were studied. Curvature-related effects both on symmetric geometry and on the (102) skew symmetric geometry were studied by the use of adjustable beam slits and 'antis.slit' placed before the sample and before the detector, respectively. The acceptable approaches to minimize the curvature-related effects in determination of a reliable tilt or twist angle were proposed. It is found that the curvature-related effects can be eliminated by the use of the methods we proposed. The dislocation densities obtained by high resolution x-ray diffraction (HRXRD) are fairly consistent with that obtained by cathodoluminescence (CL) and atomic force microscope (AFM).