Understanding Coulomb Scattering Mechanism in Ambipolar Tellurium Nanosheet Transistors

Recently, tellurium (Te), a group-VI element semiconductor, has garnered considerable attention owing to its exceptional electrical properties and high stability, offering broad application potential. However, the electron conduction mechanism in Te-based semiconductor devices remains obscure owing to the unintentional p-doping caused by the native atomic vacancies present in Te materials. Herein, we report the carrier-type-dependent Coulomb scattering mechanism in ambipolar Te field-effect transistors via high-κ dielectric passivation of Al₂O₃ using the atomic layer deposition technique. The populated excess electrons (≈5.4 × 10¹² cm^-2) after Al₂O₃ deposition lead to the presence of ambipolarity, allowing simultaneous exploration of the charge scattering mechanisms of electrons and holes in an identical Te channel. The dominant charged carrier fluctuation can be attributed to variations in the number of carriers accumulated at the SiO₂/Te and Te/Al₂O₃ interfaces through dynamic carrier trapping and detrapping from the surrounding oxide trap sites via tunneling. The determined effective trap surface density of dielectrics for electrons (≈3.2 × 10¹³ cm^-2·eV^-1) and holes (≈3.6 × 10¹³ cm^-2·eV^-1) is approximately six to seven times lower than that of Te vacancies (≈2.1 × 10¹⁴ cm^-2·eV^-1), highlighting the critical role of Te vacancies in achieving ambipolar transport. In addition, we demonstrated the NOT logic gate application based on ambipolar 2D Te FETs. Our study suggests a strategy for achieving n-type doping for complementary metal-oxide-semiconductor applications and provides insights into the charge scattering mechanisms in ambipolar Te-based electronic devices.