Understanding Coulomb Scattering Mechanism in Ambipolar Tellurium Nanosheet Transistors

Abstract

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-kappa dielectric passivation of Al2O3 using the atomic layer deposition technique. The populated excess electrons (approximate to 5.4 x 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 (approximate to 3.2 x 1013 cm-2<middle dot>eV-1) and holes (approximate to 3.6 x 1013 cm-2<middle dot>eV-1) is approximately six to seven times lower than that of Te vacancies (approximate to 2.1 x 1014 cm-2<middle dot>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.