A novel broken-gap chemical-bonded SiC/Ti2CO2 heterojunction with band to band tunneling: first-principles investigation

Abstract

A broken-gap heterojunction is a bright approach for designing tunneling field-effect transistors (TFETs) due to its distinct quantum tunneling mechanisms. In this study, we investigate the electronic structure and transport characteristics of a SiC/Ti₂CO₂ heterojunction, as well as the impacts of electric field and strain on the electronic properties via density functional theory. We determine that the interfacial atoms of the heterojunction are covalently bonded, forming a type-III heterojunction with a broken-gap. There exists band-to-band tunneling (BTBT) from the valence band (VB) of SiC to the conduction band (CB) of Ti₂CO₂. The creation of the heterojunction also enhances the carrier mobility arising from the large elastic modulus and the decrease of deformation potential. The current–voltage (I–V) characteristics of the device demonstrate a pronounced negative differential resistance (NDR) effect, along with a current that is about ten times greater than that of the vdW type-III heterojunction. Moreover, the tunneling window of SiC/Ti₂CO₂ is only slightly altered when subjected to an external electric field and vertical strain, demonstrating the remarkable stability of its type-III band alignments. Our results indicate that the SiC/Ti₂CO₂ heterojunction is useful to construct high-performance TFETs, and also introduces new ideas to design TFETs by using type-III covalent-bond heterojunctions.