Selective Epitaxial Growth Of Graphene On 4H-SiC

Graphene has shown great potential for high speed electronic device applications due to its extremely high carrier mobility and other outstanding properties.Among many approaches for fabrication of graphene, thermal decomposition of SiC for epitaxial graphene is thought to be one of the most promising options for fabrication of large-scale nano devices because of its good compatibility with existing semiconductor processing and no need for substrate transferring.However, the first step in graphene-base device technology is to form graphene nanoribbons by means of performing dry etching in O2 plasma. This step will introduce defects and dangling bonds at the edges of graphene nanoribbons, decreasing their carriers mobility. Also, the polymethyl methacrylate and the chemical wet solutions used for patterning induce an unintentional doping in the graphene sheets, altering the device performances.We propose a new method of epitaxial graphene growth in desired regions on 4H-Si C substrates including depositing 100 nm thickness Al N on the top of Si C as a capping layer, which will prevent the sublimation of Si atoms, as a result, graphene can only be growth in the regions without capping by Al N layer.This paper firstly illustrates the structure of graphene and related electronical properties and several approaches for fabrication of graphene have been introduced as well as their merits. In the end of first part, some methods to characterize graphene are referred.Secondly, mechanisms and different conditions of epitaxial graphene on two face of Si C are analyzed. Based on the method of thermal decomposition of Si C for epitaxial graphene, we describe the steps that deposit Al N on 4H-Si C substrates and mask open windows for graphene growth in detail, including cleaning substrate, depositing Al N, photolithography and etching.Finally, growth has been performed under Ar atmosphere 1mbar at temperatures rangingfrom 1400 to 1600°C based on the Si C high reactor system in institute of Semiconductor, Chinese Academy of Sciences. The formation of the graphene layer has been monitored using AFM, SEM and Raman Spectra. AFM and SEM of the surface show that Al N film can effectively prevent Si atoms sublimation under 1400°C and 1500°C. However, when the temperature reaches 1600°C, there have be defects on the surfaces of Al N film, so we conclude that the limitation temperature via this method is 1600°C. And the result of Raman Spectra show that under 1400°C/10 mins condition, there is no graphene existing. But with the increasing of time and temperature, epitaxial graphene layer shows a good quality. We also measured the electronic transport of selective graphene, the Hall mobility is 150±20cm2/Vs, which may be caused by disorder scattering of edges. These results proves a new road to fabricate graphene devices.