Heavy Si doping: The key in heteroepitaxial growth of a-plane GaN without basal plane stacking faults?

In this paper, we compare the effectiveness of two different methods regarding the reduction of defect densities in heteroepitaxially grown a-plane GaN by heavy Si doping. The insertion of well-established in situ Si x N y nanomasks leads to locally heavy Si δ-doped GaN. By increasing the Si x N y deposition time in the range from 0 to 300 s the full width at half maxima (FWHM) of the X-ray diffraction ω-scans at in-plane GaN(1100) and GaN(0002) Bragg reflections decreases from 0.55° to 0.24° and from 0.45° to 0.16°, respectively. When growing without any Si x Ny interlayer but instead with continuously heavy Si-doping, these values are further decreased to 0.13° and 0.15°, respectively. By measuring several higher order reflections and detailed evaluation of the ω-scan broadening in Williamson―Hall-plots (WHPs) a considerable reduction in defect densities and no hint of basal plane stacking faults (BSFs) were found for the heavy Si doped a-plane GaN sample. To verify this result the micro-structural properties of this sample were additionally investigated by transmission electron microscopy and cathodoluminescence (CL).