Built-In Sheet Charge As an Alternative to Dopant Pockets in Tunnel Field-Effect Transistors`

Dopant pockets in combination with a III–V heterostructure have become a staple in simulations of tunnel field-effect transistors (TFET) to achieve acceptable on-currents ( ${I} _{\mathrm{ ON}}$ ) and to break the ${I} _{\mathrm{ ON}}$ -subthreshold swing trade-off in pTFETs. Questions on the scalability and variability of these dopant pockets remain, however. We therefore propose an alternative concept using two opposite sheet charges at the tunnel junction that are realized by exploiting different bonding types. With fully quantum mechanical 30-band k.p-based simulations, we investigate two configurations that exhibit such sheet charges both at the device level and in a ring-oscillator: a lattice-matched GaAs-Ge-GaAs heterostructure TFET and a homostructure InGaAs TFET. By comparing to pocketed broken gap GaSb-InAs TFETs, we show that built-in sheet charge is a valid alternative for both nTFET and pTFET, with the prospect of lower variability and better scalability.