Self-assembled GaAs nanostructures on 4H-SiC(0001) with ultra-thin oxide layer

We investigated a molecular beam epitaxy growth of GaAs nanocrystals on 4H-SiC(0001) substrates covered by ultra-thin oxide layer. Two growth approaches were explored: direct heteroepitaxy and droplet epitaxy. Under the standard GaAs homoepitaxy conditions, direct heteroepitaxy on SiC resulted in low-density, poorly oriented GaAs nanocrystals, likely due to limited interaction between the GaAs and the underlying crystalline SiC surface. In contrast, droplet epitaxy enabled better control over the nanocrystal density and their vertical alignment. By optimizing the arsenization conditions and the oxide layer thickness, self-catalyzed GaAs nanocrystals oriented along the [111] direction were achieved. Their lateral size is about 100 nm and the height of 150–200 nm, depending on the initial Ga droplet size and crystallization parameters (temperature and As flux). These results highlight the potential of droplet epitaxy for the integration of vertically aligned III–V nanocrystals on SiC substrates, paving the way for future nanoscale photonic applications.