Effect of Growth Conditions on SiC Remote Epitaxy

Remote epitaxy is a promising growth technique for preparing freestanding epitaxial films [1]. Ultra-thin Graphene films formed on SiC substrates by Si sublimation or chemical vapor deposition using hydrocarbon is an attractive method for SiC remote epitaxy because there is no graphene transfer step. However, a problem in SiC remote epitaxy is that SiC homoepitaxial growth typically uses hydrogen carrier gas above 1500°C by chemical vapor deposition, which can damage or remove graphene. In this study, we used argon as a carrier gas to suppress graphene etching by hydrogen and investigated effects of the C/Si ratio in the supplied growth gas and pressure on SiC remote epitaxy. Epitaxial graphene was grown on n-type 4-degree off-axis 4H-SiC(0001) substrates by the Si sublimation method. SiC remote epitaxial growth was performed at 1500°C in a hot-wall CVD reactor. By depositing a highly stressed Ni stressor layer on the SiC film, the SiC-graphene interface was strained, and the SiC film was peeled off from the graphene surface by applying a thermal release tape. When SiC was grown by using typical supplied source gases with a C/Si ratio of 0.8, the graphene was etched out and could not be exfoliated. On the other hand, when SiC was grown on graphene with a high C/Si ratio above 10, SiC was successfully exfoliated from the graphene. The exfoliated SiC film was determined to be 4H polytype of SiC in the epitaxial relationship with the SiC substrate by cross-sectional transmission electron microscopy. However, when the C/Si ratio exceeded 10, graphene was grown in majority areas and the SiC-grown areas were rarely observed. To expand the SiC growth area, the effect of growth pressure was investigated. The nucleation on the film and the SiC coved area were increased with increasing pressure. These results indicate that it is important to select the appropriate C/Si ratio and pressure for SiC remote epitaxy.<br/><br/>[1] Kim, Y., Cruz, S., Lee, K. et al. Nature 544, 340 343 (2017).