Trapping and detrapping of oxide border traps in Al2O3 gate dielectric in MoS2 n-MOSFETs under PBTI stress

In this paper, we report the positive bias temperature instability (PBTI) effects of the back-gated MoS
₂
n-MOSFET with Al
₂
O
₃
gate dielectric. Multilayer MoS
₂
was used and all measurements are carried in vacuum to avoid the electric signal contamination by the top MoS
₂
surface water or oxygen molecules absorption. In the stress phase, the Id-Vg curve shifts to the positive gate bias direction. In the recovery phase, the Id-Vg shifts back completely to the fresh device curve. This indicates that voltage shift is purely due to trapping or detrapping of the oxide border traps at the MoS
₂
/Al
₂
O
₃
interface and no new traps are generated during the stress time. When applying different stress voltage and measuring the Id-Vg shift, we can calculate the oxide border trap energy density Ξ(E), which has a peak value of 6×10
¹³
cm
^-2
eV
^-1
at 0.035eV above EC of MoS
²
conduction band.