Unipolar behavior in graphene-channel field-effect-transistors with n-type doped SiC source/drain regions

To realize graphene-channel field-effect-transistors (GFETs) with unipolar behavior and high on/off current ratios, we fabricated and characterized top-gate GFETs with n-type doped SiC (n-SiC) source/drain (S/D) regions on 4H-SiC(0001) substrates. 0-2 mono-layers (MLs) of graphene were grown on a monoatomic interfacial layer called zero-layer (ZL) by vacuum annealing. The 0-2 graphene MLs on the ZL were converted into 1-3 MLs of graphene without a ZL by annealing in H₂. The GFETs with n-SiC S/D regions and 1-3 MLs of graphene without a ZL showed unipolar behavior with a high on/off current ratio of 2.7 × 10³.