EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Conventional transistor topologies are limited to static electrical functions and demand extraordinarily steep and reproducible doping concentration gradients at the junctions. Reaching the physical limits of scaling, doping-free reconfigurable field-effect transistors (RFETs), capable of integrating logic functions in a complementary design by dynamically altering the device either to p- or n-type operation even during runtime are emerging. In this respect, Ge-based RFETs have been identified as promising candidates to pave the way for low-power and high-speed future next-generation transistor technologies versus Si devices. Nevertheless, its demonstration has been restricted to bottom-up approaches impeding circuit implementability.
In this work, we demonstrate a wafer-scale fabrication scheme to embed monolithic metal-semiconductor-metal heterostructures in a RFET architecture. Polarity control of the device is achieved by two independent gates enabling to control the energy barriers at the abrupt Al-Ge heterojunctions to block the undesired carrier type. The charge carrier concentration in the Ge channel is steered by a dedicated control gate, turning the transistor ON or OFF. With respect to threshold voltages and normalized ON-currents, the proposed Ge-based RFET device is capable to outperform previous polarity-controllable architectures implemented with bottom-up grown Ge nanowires. Hence, the proposed platform may pave the way for future high-performance and low-power reconfigurable circuits, which provide promising solutions for future energy-efficient systems as well as hardware security integrated circuits.