Efficient Threshold Voltage Adjustment Technique by Dielectric Capping Effect on MoS₂ Field-Effect Transistor

In this letter, we demonstrate an efficient threshold voltage (V_th) adjustment technique by depositing single or double dielectric layers on MoS₂ field-effect transistors (FETs). We used Al₂O₃ and SiO₂ as the capping layers on the MoS₂ FET and observed different average V_th shifts of -2.39 and +7.13 V, respectively. In order to further the controllability of the dielectric capping effect, the deposition of double dielectric layers, specifically Al₂O₃ on SiO₂ and vice versa, was used for the first time. Consequently, the deposition of SiO₂ on Al₂O₃ and Al₂O₃ on SiO₂ shows an average V_th shifts of +4.92 and +4.02 V, respectively. The defect charges in the dielectric layer can induce band bending in the MoS₂ interface and adjust V_th of the MoS₂ FET. This result suggests a promising V_th adjustment technique for transition-metal dichalcogenides-based FETs.