2D Ambipolar Vertical Transistors as Control-free Reconfigurable Logic Devices

TL;DR

This paper demonstrates vertical ambipolar transistors with MoTe2 channels that can be reconfigured as n-type or p-type devices without additional gates, enabling more compact and cost-effective reconfigurable logic circuits.

Contribution

The authors fabricated control-free vertical ambipolar transistors using MoTe2 and asymmetric electrostatic gating, eliminating the need for polarity control gates in reconfigurable logic devices.

Findings

Achieved unipolar conduction by asymmetric electrostatic gating

Demonstrated temperature-dependent Schottky barrier-controlled conduction

Showed potential for higher logic density and lower cost in integrated circuits

Abstract

As transistor footprint scales down to sub-10 nm regime, the process development for advancing to further technology nodes has encountered slowdowns. Achieving greater functionality within a single chip requires concurrent development at the device, circuit, and system levels. Reconfigurable transistors possess the capability to transform into both n-type and p-type transistors dynamically during operation. This transistor-level reconfigurability enables field-programmable logic circuits with fewer components compared to conventional circuits. However, the reconfigurability requires additional polarity control gates in the transistor and potentially impairs the gain from a smaller footprint. In this paper, vertical transistors with ambipolar MoTe2 channels are fabricated using the transfer-metal method. The efficient asymmetric electrostatic gating in source and drain contacts gives rise to different Schottky barriers at the two contacts. Consequently, the ambipolar conduction is reduced to unipolar conduction due to different Schottky barrier widths for electrons and holes. The current flow direction determines the preferred carrier type. Temperature-dependent measurements reveal the Schottky barrier-controlled conduction in the vertical transistors and confirm different Schottky barrier widths with and without electrostatic gating. Without the complexity overhead from polarity control gates, control-free vertical reconfigurable transistors promise higher logic density and lower cost in future integrated circuits.