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 MoS
₂
field-effect transistors (FETs). We used Al
₂
O
₃
and SiO
₂
as the capping layers on the MoS
₂
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 Al
₂
O
₃
on SiO
₂
and vice versa, was used for the first time. Consequently, the deposition of SiO
₂
on Al
₂
O
₃
and Al
₂
O
₃
on SiO
₂
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 MoS
₂
interface and adjust V
_th
of the MoS2 FET. This result suggests a promising V
_th
adjustment technique for transition-metal dichalcogenides-based FETs.