Suppression of surface optical phonon scattering by AlN interfacial layers for mobility enhancement in MoS2 FETs

Abstract

Molybdenum disulfide (MoS₂) has been attracting attention for its theoretically outstanding electrical characteristics such as an appropriate bandgap, high mobility, and atomically thin nature. However, when MoS₂ is used to fabricate field-effect transistors (FETs), it is difficult to achieve intrinsically good performance due to severe scattering caused by charged impurities (CIs), surface roughness, and surface optical phonons (SOPs). Since SOP scattering is widely acknowledged as the dominant mechanism degrading mobility at room temperature, in this study, we aim to suppress the SOP scattering originating from high-κ oxide dielectrics (such as Al₂O₃ with a low SOP energy of 48.2 meV), by inserting aluminum nitride (AlN) interfacial layers with a high SOP energy of 81.4 meV. MoS₂ FETs with an AlN sandwich structure exhibit higher on-current levels and field-effect mobility by approximately 2.5 and 2.3 times, respectively, compared with Al₂O₃ sandwiched MoS₂ FETs. Furthermore, the suppression of SOP scattering by the AlN interfacial layers can be confirmed by the power-law relationship between temperature and mobility, μ∝T^−γ. As the number of interfaces between MoS₂ and AlN increases from 0 to 2, the γ value decreases from 1.3 to 0.12.