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

Abstract

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 500–1500°C. 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 940–1245°C 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 H 2/He (1:1) plasma at 940°C 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.