Thermal removal of oxide and carbide from 6H–SiC surfaces before molecular beam epitaxial growth of GaN

We have demonstrated growth of good quality GaN onto C-terminated 6H–SiC substrates by using a substrate-heating holder in a nitrogen–plasma molecular beam epitaxy MBE.system. This substrate holder system can heat samples to the temperature region of 500–15008C. Near-band-edge emissions have been observed from some of these epilayers, depending primarily on the substrate surface conditions. Auger electron spectroscopy AES.and X-ray photoelectron spectroscopy XPS.measurements show that the temperatures of 940–12458C are necessary to thermally desorb the oxide and carbide from 6H–SiC substrates. Structural analysis by X-ray diffraction XRD.and photoluminescence PL.indicates very good in-plane alignment of the GaN epilayers as the substrates are cleaned using H2rHe 1:1.plasma at 9408C for 100 min. The full-width at half-maximum FWHM.values of the XRD and PL peaks are about 90 arc-second and 1.4 meV at 4.3 K for C-terminated 6H–SiC substrates, respectively. The results show that the deep-level recombination at 2.17 eV yellow band. depends on the surface situation of the SiC substrate. q2000 Elsevier Science B.V. All rights reserved.