A U-Gate InGaAs/GaAsSb Heterojunction TFET of Tunneling Normal to the Gate With Separate Control Over ON- and OFF-State Current

Abstract

A U-gate vertical tunneling field-effect transistor (TFET) of band-to-band tunneling (BTBT) normal to the gate at low operation voltages is proposed and investigated by TCAD simulation. In this structure, drive current and OFF-state leakage current can be separately controlled by the insertion of a spacer layer between the channel and drain layers. The dominant mechanisms for drive current and OFF-state leakage are BTBT and source-to-drain tunneling (SDT), respectively. A modified structure of side gates and a hetero-spacer enables high-performance InGaAs/GaAsSb heterojunction TFETs with low OFF-state leakage. Drive current as high as 520 $\mu \text{A}/\mu \text{m}$ with an $I_{ \mathrm{\scriptscriptstyle ON}}/I_{ \mathrm{\scriptscriptstyle OFF}}$ ratio of 107 at an overdrive voltage of 0.3 V was achieved in an InGaAs/GaAsSb heterojunction TFET of a small effective bandgap (0.02 eV). Furthermore, this U-gate TFET structure is fully compatible to VLSI technology without any complicated fabrication steps.