Optimizing Al-doped ZrO₂ as the gate dielectric for MoS₂ field-effect transistors

In this work, we investigate the effects on the electrical properties of few-layered MoS₂ field-effect transistors (FETs) following Al incorporation into ZrO₂ as the gate dielectrics of the devices. A large improvement in device performance is achieved with the Al-doped ZrO₂ gate dielectric when Zr:Al = 1:1. The relevant MoS₂ transistor exhibits the best electrical characteristics: high carrier mobility of 40.6 cm² V^-1 s^-1 (41% higher than that of the control sample, and an intrinsic mobility of 68.0 cm² V^-1 s^-1), a small subthreshold swing of 143 mV dec^-1, high on/off current ratio of 6 × 10⁶ and small threshold voltage of 0.71 V. These are attributed to the facts that (i) Al incorporation into ZrO₂ can decrease its oxygen vacancies; densify the dielectric film; and smooth the gate dielectric surface, thus reducing the traps at/near the Zr_0.5Al_0.5O _y /MoS₂ interface and the gate leakage current; (ii) adjusting the dielectric constant of the gate dielectric to an appropriate value, which achieves a reasonable trade-off between the gate screening effect on the Coulomb-impurity scattering and the surface optical phonon scattering. These results demonstrate that optimized Zr_0.5Al_0.5O_y is a potential gate dielectric material for MoS₂ FET applications.