Tellurium as a successor of silicon for extremely scaled nanowires: a first-principles study

Abstract

Trigonal-Tellurium (t-Te) has recently garnered interest in the nanoelectronics community because of its measured high hole mobility and low-temperature growth. However, a drawback of tellurium is its small bulk bandgap (0.33 eV), giving rise to large leakage currents in transistor prototypes. We analyze the increase of the electronic bandgap due to quantum confinement and compare the relative stability of various t-Te nanostructures (t-Te nanowires and layers of t-Te) using first-principles simulations. We found that small t-Te nanowires (≤4 nm2) and few-layer t-Te (≤3 layers) have bandgaps exceeding 1 eV, making Tellurium a very suitable channel material for extremely scaled transistors, a regime where comparably sized silicon has a bandgap that exceeds 4 eV. Through investigations of structural stability, we found that t-Te nanowires preferentially form instead of layers of t-Te since nanowires have a greater number of van der Waals (vdW) interactions between the t-Te-helices. We develop a simplified picture of structural stability relying only on the number of vdW interactions, enabling the prediction of the formation energy of any t-Te nanostructure. Our analysis shows that t-Te has distinct advantages over silicon in extremely scaled nanowire transistors in terms of bandgap and the t-Te vdW bonds form a natural nanowire termination, avoiding issues with passivation.