Full Energy Spectra Of Interface State Densities For N- And P-Type Mos2 Field-Effect Transistors

2D materials are promising to overcome the scaling limit of Si field-effect transistors (FETs). However, the insulator/2D channel interface severely degrades the performance of 2D FETs, and the origin of the degradation remains largely unexplored. Here, the full energy spectra of the interface state densities (D-it) are presented for both n- and p- MoS2 FETs, based on the comprehensive and systematic studies, i.e., full rage of channel thickness and various gate stack structures with h-BN as well as high-k oxides. For n-MoS2, D-it around the mid-gap is drastically reduced to 5 x 10(11) cm(-2) eV(-1) for the heterostructure FET with h-BN from 5 x 10(12) cm(-2) eV(-1) for the high-k top-gate. On the other hand, D-it remains high, approximate to 10(13) cm(-2) eV(-1), even for the heterostructure FET for p-MoS2. The systematic study elucidates that the strain induced externally through the substrate surface roughness and high-k deposition process is the origin for the interface degradation on conduction band side, while sulfur-vacancy-induced defect states dominate the interface degradation on valance band side. The present understanding of the interface properties provides the key to further improving the performance of 2D FETs.