Cross-sectional spatially resolved cathodoluminescence study of cubic GaN films grown by metalorganic vapor phase epitaxy on free-standing (0 0 1) 3C-SiC and GaAs substrates

Metalorganic vapor phase epitaxy (MOVPE) of cubic GaN (c-GaN) films on free-standing (0 0 1) 3C-SiC substrate was studied in terms of structural and optical properties. Similar to the case for the c-GaN growth on (0 0 1) GaAs substrates, approximately 20-nm-thick GaN nucleation layer deposited at low temperature (∼ 600 ^{{ring operator}} C) was essential in accommodating the lattice-mismatch between c-GaN and SiC. Also, low group-V-group-III supply ratio (∼ 30) was preferable to maintain the cubic phase. Because the SiC substrate had plenty of surface prongs and scratches due presumably to the wafer polishing, macroscopic surface morphology, crystal coherency, and optical quality of the c-GaN films on SiC were inferior to those of the films on GaAs. However, cross-sectional spatially resolved cathodoluminescence (CL) measurements revealed the presence of high quality areas in between the prongs. The results indicate a potential of 3C-SiC substrates for future realization of c-GaN-based optoelectronic devices.