GaN remote epitaxy on a pristine graphene buffer layer via controlled graphitization of SiC

Freestanding semiconductor membranes hold significant potential for heterogeneous integration technology and flexible electronics. Remote epitaxy, which leverages electrostatic interactions between epilayers and substrates through two-dimensional (2D) materials such as graphene, offers a promising solution for fabricating freestanding single-crystal membranes. Although the thinness, uniformity, and cleanness of 2D materials need to be meticulously controlled to enable the remote epitaxy of high-quality thin films, attaining such ideal growth templates has been challenging thus far. In this study, we demonstrate a controlled graphitization method to form a pristine graphene buffer layer (GBL) directly on SiC substrates and utilize this GBL template for GaN remote epitaxy. The quasi-two-dimensional GBL layer obtained by the method is completely free of damage or contamination, facilitating strong epitaxial interaction between the GaN epilayer and the SiC substrate. Furthermore, we reveal that a two-step growth of GaN on this GBL template enables the formation of single-crystal GaN epilayers and their exfoliation. Thus, this study represents an important step toward developing high-quality, freestanding semiconductor membranes.