Properties of GaN grown on Si(111) substrates dependent on the thickness of 3C-SiC intermediate layers

Crack-free GaN epilayers were grown with the mask less epitaxial lateral overgrowth (ELO) on Si substrates with various thicknesses of 3C-SiC intermediate layers. The defects in 3C-SiC and GaN layers were studied to reveal the impact of 3C-SiC intermediate layer on GaN epitaxy. In the 3C-SiC layer, a gradient density of stacking faults (SFs) was observed along the growth direction. Most of the SFs locate in the first 500-nm-thick 3C-SiC layer. Thanks to the maskless ELO method, the defects in under layer could not extend into GaN layer, even grown on a 100-nm-thick 3C-SiC layer with high density. The threading dislocation density in GaN varies in the range of ∼(1 ± 0.3) × 10⁹ cm⁻². Investigation of GaN nucleation indicated a correlation between GaN quality and surface roughness of 3C-SiC layers. Meanwhile, the surface morphology of 3C-SiC is affected by double positioning domains, which revealed as a result of strain relaxation process during growth on Si substrate.