Tuning graphene/silicon Schottky barrier height by chemical doping

We demonstrate that the Schottky barrier height of graphene/silicon heterojunction can be efficiently tuned by chemical methods. The accurate value of Schottky barrier height can be extracted by measuring the temperature-dependent IV curve of graphene/silicon heterojunction. The height value is calculated from the slope of Richardson plot (logI/T2 vs. 1/T) of the reverse current region dominated by thermionic emission. Chemical dopants like AuCl3 and NH4F are employed to tune the Fermi level of graphene, and the doping effect is verified by gate-dependent transfer characteristics. Further experiments investigate the influence of doping time and dopant concentration on graphene's doping level. The results show that the doping level gradually increases as the doping time or concentration increase, indicating the possibility to precisely control doping level. In our experiments, the Schottky barrier height of graphene/silicon junction can be tuned between 0.38 to 0.6 eV after doping treatment.