GaN On 6H-SiC – Structural And Optical Properties

Recent progress in the growth of high quality 6H-SiC single crystals has led to an ideal substrate material for GaN epitaxial films. Nearly matching lattice constants of wurzite GaN to 6H-SiC in the hexagonal plane can reduce strain effects at the interface. We employed the sublimation sandwich method to grow single crystal layers at reasonable growth rates with free carrier concentrations of 2×1017 cm-3. Very sharp x-ray diffraction peaks of the GaN (0002) plane are obtained indicating the high quality of this system (Δ(2θ) < 0.1 degrees). These findings are directly reflected in the optical properties. The photoluminescence is dominated by a single sharp exciton line, impurity related donor acceptor transitions are seen with very weak intensities. However, at lower energies the internal luminescence transitions of the 3d transition metal ions Fe and V are observable. The incorporation of Fe is confirmed by electron paramagnetic resonance.