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Novel devices and emerging technologies

In order to maintain also in the future the pace of growth of the electronic industry observed in the last few decades, new materials, new technologies and new device concepts are required to replace the standard silicon CMOS technology, which has been the workhorse in digital circuits for a long time and is now approaching its scalability limits. The projects described in this section, carried out in the framework of European research programs and in cooperation with the leading European industrial and research institutions, operate in this direction.

 

Carbon-based nanoelectronic devices

Carbon in its various forms (i.e., two-dimensional monoatomic layer known as graphene, or carbon nanotubes) is considered one of the most promising materials for replacing silicon in high-speed nanoelectronic devices, due to its excellent electronic and thermal properties. However, before reaching that goal, a number of problems have to be solved concerning not only the technological aspects, but also the device architecture and optimization. This research project focuses on the investigation of novel carbon-based device concepts and on the understanding of their physical properties, through the use of in-house developed simulation codes.

 

III-V semiconductor transistors

According to the International Technology Roadmap for Semiconductors (ITRS), a consortium of the main worldwide industrial and research actors in the semiconductor field having the goal of identifying the main needs of the semiconductor industry in the coming years, III-V semiconductors (e.g. InGaAs) are indicated to replace silicon as channel material of the n-MOSFETs in CMOS circuits around year 2018. The motivation is related to the high electronic velocity typical of such materials. However, several problems are still open: among these are the high leakage currents and the large number of traps. Modeling is an essential aspect to improve the device understanding and explore the various options. This research project aims at the development of suitable physically-based simulation tools for such devices, and their use in the optimization process.

 

Tunnel-effect transistors

In order to scale down the supply voltage in CMOS circuits and reduce the power dissipation without degrading the speed performance, transistors with low threshold voltage and high subthreshold current slope are necessary. Tunnel-based Field Effect Transistors (TFETs) are one of the open possibilities. However, practical realization of TFETs so far have shown poor on-state current and insufficient subthreshold slope. The solution of the problem requires in depth analyses based on physically sound simulation models, and the identification of novel device topologies in order to optimize the current characteristics.

 

Phase-Change Memories (PCM)

Phase-Change Memory devices have intensively been studied in the last years and are now (2014) in the early production stage. Phase-change materials like chalcogenides, known from the early 1960s, exhibit a reversible transition between a crystalline and an amorphous phase, characterized by a significant change in optical reflectivity and electrical resistivity. The strong difference in resistivity of the two phases makes chalcogenide materials suitable candidates for solid-state nonvolatile memories. Some chalcogenide glasses exhibit an “Ovonic” threshold-switching in the amorphous phase, corresponding to a negative differential resistance in the current-voltage characteristic before the occurrence of the phase change. Although many interpretations of the phenomenon have been proposed, a sound physical theory is still lacking. The subject is intensively studied in cooperation with leading Companies in the field.