Chemical Vapor Deposition of Graphene on Self-Limited SiC Interfacial Layers Formed on Silicon Substrates for Heterojunction Devices

Abstract

Direct chemical vapor deposition (CVD) of graphene on any desired substrate is always required to manufacture high-quality heterojunctions with excellent interfacial properties. Herein, the growth of graphene on cubic-silicon carbide (3C-SiC) surfaces using conventional high-temperature direct thermal CVD and plasma-enhanced CVD (PECVD) is explored, which is hardly reported to date. Since 3C-SiC substrates are not available, the controlled self-limited 3C-SiC layers on the Si(100) substrates were grown at different temperatures (900–1200 °C) via thermal-CVD technique to obtain virtual 3C-SiC substrates. The direct production of graphene via thermal CVD could not be achieved on such 3C-SiC surfaces. The density functional theory and molecular dynamics simulations confirm that the carbon atom diffusion over the 3C-SiC surface is extremely low, like over the Si surface, which leads to no graphene growth. A similar growth mechanism may be attributed to their similar crystal structure viz diamond cubic for Si and zinc blend for 3C-SiC. However, graphene nanowalls (GNWs) were successfully grown on both Si and 3C-SiC/Si surfaces at 700 °C via the PECVD technique, where similar surface morphologies were observed because the growth mechanism of GNWs is independent of substrate type. Moreover, I–V characterization was performed for different SiC/Si heterostructures and their corresponding GNWs/SiC/Si heterostructures, respectively. The current conduction improved considerably more for GNW/SiC/Si heterostructures as compared to SiC/Si heterostructures, but the creation of a SiC interfacial layer as well as its quality affected the conductivity of GNWs/SiC/Si heterostructures. The inevitable formation of an interfacial SiC layer during the direct graphene growth via thermal CVD on Si substrates can seriously affect the performance of graphene/Si heterojunction devices. Hence, PECVD growth of graphene is an ideal option to fabricate graphene/Si heterojunction devices with excellent interfacial properties or graphene/3C-SiC/Si heterojunction devices for various electronic/optoelectronic applications such as gas sensors and photovoltaic devices.