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A promising approach to advance electronics beyond static operations is to enhance state-ofthe- art systems by the functional diversification of transistors. Here, we experimentally demonstrate that an ultra-thin Ge channel implemented on a Si on insulator platform enables run-time switchable symmetric pand n-type field-effect transistor operability as well as the prominent feature of distinct room-temperature negative differential resistance. Temperature dependent bias spectroscopy is utilized to map electronic transport in these so called negative differential resistance mode reconfigurable transistors. Thereof, a profound understanding of the involved transport physics and electrostatic gating mechanisms is obtained and evaluated. Further, we show that a multi-gate negative differential resistance reconfigurable transistor can effectively replace a cascode of negative differential resistance devices, contributing to a smaller area footprint, and reduced latency of critical paths. Notably, the experimentally obtained multi-heterojunction transistors constitute the first chip-scale platform that combines efficient polarity control as well as sizeand energy-efficient room-temperature negative differential resistance, providing an inherent component of emerging neuromorphic computing.

Here, we present a Ge based reconfigurable transistor, capable of dynamic run-time switching between n- and p-type operation with enhanced performance compared to state-of-the- art Si devices. Thereto, we have monolithically integrated an ultra-thin epitaxial and defect-free Ge layer on a Si on insulator platform. To evade the commonly observed process variability of Ni-germanides, Al-Si-Ge multi-heterojunction contacts have been employed, providing process stability and the required equal injection capabilities for electrons and holes. Integration into a three top-gate transistor enables effective polarity control and efficient leakage current suppression to limit static power dissipation. Exploiting the advantages of multi-gate transistors, combinational wired-AND gates are shown to be capable of extending a single transistor to a logic gate. Notably, the obtained Al-Si-Ge multi-heterojunction reconfigurable transistors constitute the first CMOS compatible platform to combine efficient polarity control enabling the envisioned performance enhancements of Ge based reconfigurable transistors.

Abstract In this work, bottom‐up Al–Si–Al nanowire (NW) heterostructures are presented, which act as a prototype vehicle toward top‐down fabricated nanosheet (NS) and multi‐wire (MW) reconfigurable field‐effect transistors (RFETs). Evaluating the key parameters of these transistors regarding the on‐ and off‐currents as well as threshold voltages for n‐ and p‐type operation exhibit a high degree of symmetry. Most notably also a low device‐to‐device variability is achieved. In this respect, the investigated Al–Si material system reveals its relevance for reconfigurable logic cells obtained from Si NSs. To show the versatility of the proposed devices, this work reports on a combinational wired‐AND gate obtained from a multi‐gate RFET. Additionally, up‐scaling the current is achieved by realizing a MW RFET without compromising reconfigurability. The Al–Si–Al platform has substantial potential to enable complex adaptive and self‐learning combinational and sequential circuits with energy efficient and small footprint computing paradigms as well as for native components for hardware security circuits.

Abstract Reconfigurable field‐effect transistors, capable of being dynamically programmed during run‐time, overcome the static nature of conventional complementary metal‐oxide semiconductors by reducing the transistor count and the circuit path delay. Thereby, SiGe and Ge are predicted to boost drive currents, switching speed and to reduce power consumption. Nevertheless, Ge‐based reconfigurable field‐effect transistor prototypes have so far fallen short in reaching both the promised performance due to interface instability to their contacts and gate oxides, as well as in reaching the current–voltage symmetry necessary for circuit applicability. Here, a top‐down fabricated SiGe‐based reconfigurable transistor technology is reported that is comprised of a vertical Si‐Si0.67Ge0.33 heterostructure enabling the envisioned high and symmetric on‐currents of both n‐ and p‐type operation. Monolithic integration with single‐elementary crystalline Al contacts alleviates process variability compared to conventional Ni‐silicide/Ni‐germanide contacts and introduces an ultra‐thin Si interlayer providing stability and equal injection efficiency of holes and electrons. The implementation of a three top‐gate transistor in combination with a hysteresis‐free Si/SiO2/HfO2 gate stack enhances polarity control and leakage current suppression to limit static power dissipation. Importantly, the obtained Al‐Si‐SiGe multi‐heterojunction and advanced reconfigurable transistor design is the first Ge‐based technology showing the envisioned stability and performance enhancements.

Abstract Metal‐semiconductor heterostructures providing geometrically reproducible and abrupt Schottky nanojunctions are highly anticipated for the realization of emerging electronic technologies. This specifically holds for reconfigurable field‐effect transistors, capable of dynamically altering the operation mode between n‐ or p‐type even during run‐time. Targeting the enhancement of fabrication reproducibility and electrical balancing between operation modes, here a nanoscale Al‐Si‐Al nanowire heterostructure with single elementary, monocrystalline Al leads and sharp Schottky junctions is implemented. Utilizing a three top‐gate architecture, reconfiguration on transistor level is enabled. Having devised symmetric on‐currents as well as threshold voltages for n‐ and p‐type operation as a necessary requirement to exploit complementary reconfigurable circuits, selected implementations of logic gates such as inverters and combinational wired‐AND gates are reported. In this respect, exploiting the advantages of the proposed multi‐gate transistor architecture and offering additional logical inputs, the device functionality can be expanded by transforming a single transistor into a logic gate. Importantly, the demonstrated Al‐Si material system and thereof shown logic gates show high compatibility with state‐of‐the‐art complementary metal‐oxide semiconductor technology. Additionally, exploiting reconfiguration at the device level, this platform may pave the way for future adaptive computing systems with low‐power consumption and reduced footprint, enabling novel circuit paradigms.