MOVPE of AlN-free hexagonal GaN/cubic SiC/Si heterostructures for vertical devices

The heterostructures of GaN/SiC/Si were prepared without using AlN or AlGaN buffer layers (AlN buffers) in the metalorganic vapor phase epitaxy of GaN on SiC. GaN (0 0 0 1) with specular surface was obtained. The AlN buffers are usually used in the conventional growth of GaN on SiC due to the poor nucleation of GaN on SiC. Instead, the nucleation of GaN was controlled by varying the partial pressure of H2 in the carrier gas, the mixture of H2 and N2, during the low-temperature (600 °C) growth of GaN (LT-GaN). After the LT-GaN, the high-temperature (1000 °C) growth of GaN was performed using pure H2 as the carrier gas. The epitaxial film of cubic SiC (1 1 1) on a Si (1 1 1) substrate was used as the SiC template. Increasing the partial pressure of H2 in the carrier gas decreased the coverage of SiC surface by LT-GaN. It is suggested that the hydrogen atoms adsorbed on the surface of SiC is preventing the nucleation of GaN.