Vertical Current Transport in Monolayer MoS₂ Heterojunctions with 4H-SiC Fabricated by Sulfurization of Ultra-Thin MoOx Films

In this paper, we report on the growth of highly uniform MoS 2 films, mostly consisting of monolayers, on SiC surfaces with different doping levels (n- SiC epitaxy, ~10 16 cm -3 , and n + SiC substrate, ~10 19 cm -3 ) by sulfurization of a pre-deposited ultra-thin MoO x films. MoS 2 layers are lowly strained (~0.12% tensile strain) and highly p-type doped (<N h >≈4×10 19 cm −3 ), due to MoO 3 residues still present after the sulfurization process. Nanoscale resolution I-V analyses by conductive atomic force microscopy (C-AFM) show a strongly rectifying behavior for MoS 2 junction with n - SiC, whereas the p + MoS 2 /n + SiC junction exhibits an enhanced reverse current and a negative differential behavior under forward bias. This latter observation, indicating the occurrence of band-to-band-tunneling from the occupied states of n + SiC conduction band to the empty states of p + MoS 2 valence band, is a confirmation of the very sharp hetero-interface between the two materials. These results pave the way to the fabrication of ultra-fast switching Esaki diodes on 4H-SiC.