Combined effects of Ga, N, and Al codoping in solution grown 3C-€“SiC

• We report on Ga-doped 3C–SiC epitaxial layers grown on on-axis (0001) 6H–SiC substrates using the vapor-liquid-solid technique and different melts. The resulting samples have been investigated using secondary ion mass spectroscopy(SIMS), micro-Raman spectroscopy and, finally, low temperature photoluminescence (LTPL) spectroscopy. From SIMS measurements we find Ga concentrations in the range of , systematically accompanied by high nitrogen content. In good agreement with these findings, the spectra show that the Ga-doped samples are -type, with electron concentrations close to . As expected, the LTPL spectra are dominated by strong N–Ga donor-acceptor pair (DAP) transitions. In one sample, a weak additional N–Al DAP recombination spectrum is also observed, showing the possibility to have accidental codoping with Ga and Al simultaneously. This was confirmed on a non-intentionally doped 3C–SiC (witness) sample on which, apart of the usual N and Al bound exciton lines, a small feature resolved at 2.35 eV comings from neutral Ga bound excitons. Quantitative analyses of the DAP transition energies in the Ga-doped and witness sample gave 346 meV for the optical binding energy of Ga acceptors in 3C–SiC against 251 meV for the Al one. The conditions for the relative observa-tion of Ga and Al related LTPL features are discussed and the demonstration of room temperature luminescence using Ga doping is done.

Subject headings

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

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