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The modelling of conventional and novel memory devices has gained significant traction in recent years. This is primarily because the need to store increasingly larger amount of data demands a better understanding of the working of the novel memory devices, to enable faster development of the future technology generations. Furthermore, in-memory computing is also of great interest from the computational perspectives, to overcome the data transfer bottleneck that is prevalent in the von-Neumann architecture. These important factors necessitates the development of comprehensive TCAD simulation tools that can be used for modeling carrier dynamics in the gate oxides of the Flash type memory cells. In this work, we introduce the kinetic Monte Carlo module that we have developed and integrated within the Nano Electronic Simulation Software (NESS) - to model electronic charge transport in Flash memory type structures. Using the developed module, we perform retention time analysis for a polyoxometalate (POM) molecule-based charge trap flash memory. Our simulation study highlights that retention characteristics for the POM molecules has a unique features that depends on the properties of the tunneling oxide.

openaire: EC/H2020/638173/EU//iTPX Recent advances in the photoluminescent cooling of doped glasses provoke the question of whether similar progress is possible in electroluminescent cooling (ELC), and if so, what are the conditions for observing it at high powers. Here, we establish a simulation framework for III-V intracavity double-diode structures (DDSs) intended for studying ELC and introduce and analyze the most relevant figures of merit for the recently measured devices exhibiting the highest reported quantum efficiency of 70%. In essence, the DDSs optically couple a GaInP/GaAs double heterojunction light-emitting diode (LED) and a GaAs p-n homojunction photodetector (PD), integrated as a single device. The modeling framework couples the drift-diffusion charge transport model with a photon transport model and uses our recent experimental measurements for validation and the extraction of important material parameters. Results show that the model can accurately describe the experimental behavior over many orders of magnitude and suggest that the internal efficiency of the LED already exceeds the cooling threshold. Directly observing cooling in the presently studied devices, however, is still hindered by bottlenecks arising from the surface recombination at the LED walls and recombination losses in the PD.

In this paper, we investigate, by combining electrical measurements with an atomistic-To-circuit modeling approach, the conductance of doped standalone multiwall carbon nanotubes (CNTs) as a viable candidate for the next generation of back-end-of-line interconnects. Ab initio simulations predict a doping-related shift of the Fermi level, which reduces shell chirality variability and improves electrical resistivity up to 90% by converting semiconducting shells to metallic. Electrical measurements of Pt-salt-doped CNTs provide up to 50% of resistance reduction, which is a milestone result for future CNT interconnect technology. Moreover, we find that defects and contacts introduce additional resistance, which limits the efficiency of doping, and are the primary cause for the mismatch between theoretical predictions and experimental measurements on doped CNTs.

In this work, we study 2.1nm-diameter uniaxial strained Si gate-all-around nanowire field-effect transistors, focusing on the electron mobility and the variability due to random discrete dopants (RDDs). Firstly, we extract the electron effective masses under various strains from Density Functional Theory (DFT) simulations. Secondly, we present the impact of the strain on the electron mobility in the Si nanowire using the Kubo-Greenwood formalism with a set of multi-subband phonon, surface roughness, and ionized impurity scattering mechanisms. Finally, we perform quantum transport simulations to investigate the effect of RDD on the threshold voltage and ON-state current variation.

openaire: EC/H2020/638173/EU//iTPX Electroluminescent (EL) cooling of semiconductors has received increasing attention in recent years. To optimize the performance of devices intended for EL cooling, special care is needed in minimizing electrical losses resulting from e.g. potential barriers, and optical losses resulting from e.g. parasitic absorption. In this work, we introduce and explore a full-device modeling tool for arbitrary planar photonic devices by coupling together the interference-exact radiative transfer equation (IFRTE) of photon transport and drift-diffusion (DD) equations of carrier transport. The IFRTE coupled with DD represents a fully self-consistent model of lossy wave optics and carrier transport, connecting emission and photon recycling with electron and hole dynamics. We deploy the model to study and optimize photon emission and absorption as well as photocarrier collection in double-diode structures for EL cooling.

In this paper, we report a hierarchical simulation\ud study of the electromigration problem in Cu-CNT composite\ud interconnects. Our work is based on the investigation of the\ud activation energy and self-heating temperature using a multiscale\ud electro-thermal simulation framework. We first investigate the\ud electrical and thermal properties of Cu-CNT composites, including\ud contact resistances, using the Density Functional Theory and\ud Reactive Force Field approaches, respectively. The corresponding\ud results are employed in macroscopic electro-thermal simulations\ud taking into account the self-heating phenomenon. Our simulations\ud show that although Cu atoms have similar activation\ud energies in both bulk Cu and Cu-CNT composites, Cu-CNT\ud composite interconnects are more resistant to electromigration\ud thanks to the large Lorenz number of the CNTs. Moreover,\ud we found that a large and homogenous conductivity along the\ud transport direction in interconnects is one of the most important\ud design rules to minimize the electromigration.

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We employ an advanced three-dimensional (3D) electro-thermal simulator to explore the physics and potential of oxide-based resistive random-access memory (RRAM) cells. The physical simulation model has been developed recently, and couples a kinetic Monte Carlo study of electron and ionic transport to the self-heating phenomenon while accounting carefully for the physics of vacancy generation and recombination, and trapping mechanisms. The simulation framework successfully captures resistance switching, including the electroforming, set and reset processes, by modeling the dynamics of conductive filaments in the 3D space. This work focuses on the promising yet less studied RRAM structures based on silicon-rich silica (SiOx) RRAMs. We explain the intrinsic nature of resistance switching of the SiOx layer, analyze the effect of self-heating on device performance, highlight the role of the initial vacancy distributions acting as precursors for switching, and also stress the importance of using 3D physics-based models to capture accurately the switching processes. The simulation work is backed by experimental studies. The simulator is useful for improving our understanding of the little-known physics of SiOx resistive memory devices, as well as other oxide-based RRAM systems (e.g. transition metal oxide RRAMs), offering design and optimization capabilities with regard to the reliability and variability of memory cells.

openaire: EC/H2020/638173/EU//iTPX We develop a coupled electronic charge and photon transport simulation model to allow for deeper analysis of our recent experimental studies of intracavity double diode structures (DDSs). The studied structures consist of optically coupled AlGaAs/GaAs double heterojunction light emitting diode (LED) and GaAs p–n-homojunction photodiode (PD) structure, integrated as a single semiconductor device. The drift–diffusion formalism for charge transport and an optical model, coupling the LED and the PD, are self-consistently applied to complement our experimental work on the evaluation of the efficiency of these DDSs. This is to understand better their suitability for electroluminescent cooling (ELC) demonstration, and shed further light on electroluminescence and optical energy transfer in the structures. The presented results emphasize the adverse effect of non-radiative recombination on device efficiency, which is the main obstacle for achieving ELC in III-V semiconductors.

In this paper, we report a hierarchical simulation study of the electromigration (EM) problem in Cu-carbon nanotube (CNT) composite interconnects. This paper is based on the investigation of the activation energy and self-heating temperature using a multiscale electrothermal simulation framework. We first investigate the electrical and thermal properties of Cu-CNT composites, including contact resistances, using the density functional theory and reactive force field approaches, respectively. The corresponding results are employed in macroscopic electrothermal simulations taking into account the self-heating phenomenon. Our simulations show that although Cu atoms have similar activation energies in both bulk Cu and Cu-CNT composites, Cu-CNT composite interconnects are more resistant to EM thanks to the large Lorenz number of the CNTs. Moreover, we found that a large and homogenous conductivity along the transport direction in interconnects is one of the most important design rules to minimize the EM.