A Top-Down Platform Enabling Ge Based Reconfigurable Transistors

Abstract

Conventional field-effect transistor (FET) concepts are limited to static electrical functions and demand extraordinarily steep and reproducible doping concentration gradients. Reaching the physical limits of scaling, doping-free reconfigurable field-effect transistors (RFETs) capable of dynamically altering the device operation between p- or n-type, even during runtime, are emerging device concepts. In this respect, Ge has been identified as a promising channel material to enable reduction of power consumption and switching delay of RFETs. Nevertheless, its use has been limited to simulations and bottom-up demonstrators not compatible with complex circuit technology. In this work, a deterministic top-down fabrication scheme is demonstrated to realize a Ge-based RFET architecture and exploring realizations with three independent gates. Polarity control and leakage current suppression are enabled by the specific injection of charge carriers through gated Al-Ge heterojunctions and the introduction of a blocking electrostatic energy barrier. Further, the choice of monolithic Al/Ge contacts alleviates process variability compared to Ni-germanide contacts presenting a top-down technology platform for Ge-based RFETs. Our device concept is a first step toward future integrated high-performance and low-power reconfigurable circuits, providing a platform for future energy-efficient systems as well as hardware security integrated circuits.