A high temperature AIN template was grown on sapphire substrate by metalorganic chemical vapor deposition. AFM results showed that the root mean square of the surface roughness was just 0.11 nm. Optical transmission spectrum and high resolution X-ray diffraction (XRD) characterization both proved the high quality of the AIN template. The XRD (002) rocking curve full width at half maximum (FWHM) was about 53.7 arcsec and (102) FWHM was about 625 arcsec. The densities of screw threading dislocations (TDs) and edge TDs were estimated to be ~ 6 × 106 cm−2 and ~ 4.7 × 109 cm−2. AlGaN of Al composition 80.2% was further grown on the AIN template. The RMS of the surface roughness was about 0.51 nm. XRD reciprocal space mapping was carried out to accurately determine the Al composition and relaxation status in the AlGaN epilayer. The XRD (002) rocking curve FWHM of the AlGaN epilayer was about 140 arcsec and (102) FWHM was about 537 arcsec. The density of screw TDs was estimated to be ~ 4 × 107 cm−2 and that of edge TDs was ~ 3.3 × 109 cm−2. These values all prove the high quality of the AIN template and AlGaN epilayer.
source: iopscience
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