1,721,141 research outputs found
Memory devices—Non-volatile memories
No full textIn this entry, the most important non-volatile memories used for a wide variety of applications are presented, with detailed information on their structural and functional properties. The first part addresses charge-based memories, including read-only memories, electrically programmable read-only memories, electrically erasable and programmable read-only memories, and flash memories. In a broad sense, all them can be considered non-volatile read-only memories, meaning that reading the stored information can be performed in a relatively short time, but programming and erasing require much longer times, if at all possible. The second part of the presentation encompasses non-volatile memories which exhibit similar read/write (R/W) access times, and can thus be regarded as random-access memories to all effects. More specifically, we illustrate magnetic memories, ferroelectric memories, phase-change memories and resistive memories, and discuss their future market perspectives
Memory devices – Volatile memories
No full textIn this Encyclopedia entry, volatile random-access memories used for a wide variety of applications are presented. More specifically, the structural and functional properties of static and dynamic RAMs, including cell topologies, cell array organizations, reading and writing procedures, reliability issues and typical applications are illustrated with a detail compatible with the allowed entry size. Content addressable memories are also treated in the final part of this entry. Conclusions and future trends complete the presentation
Impact of Strain on Tunneling Current and Threshold Voltage in III-V Nanowire TFETs
Full text linkA simulation study on the effects of different strain configurations on n-type III-V-based nanowire tunnel-FETs is presented, with the aim to determine optimal strain conditions to enhance device performance. We find that both the biaxial tensile and the uniaxial compressive stress shift up the valence band. Biaxial stress, however, lowers the conduction band as well, thus providing the largest reduction of the energy bandgap. Instead, the gap variation is limited for the biaxial compressive and uniaxial tensile strains. Moreover, for these strain conditions, the lowest conduction subband is not connected to the highest valence subband via the imaginary wave vector but to a lower one. This leads to an effective bandgap higher than the expected, which reflects into a large threshold increase and a degradation of the ON-state current
Theoretical analysis and modeling for nanoelectronics
No full textIn this paper we review the evolution of Microelectronics and its transformation into Nanoelectronics, following the predictions of Moore's law, and some of the issues related with this evolution. Next, we discuss the requirements of device modeling and the solutions proposed throughout the years to address the physical effects related with an extreme device miniaturization, such as hot-electron effects, band splitting into multiple sub-bands, quasi-ballistic transport and electron tunneling. The most important physical models are shortly highlighted, and a few simulation results of heterojunction TFETs are reported and discussed
A Coherent Extension of the Transport Equations in Semiconductors Incorporating the Quantum Correction: Part II – Collective Transport
No full textThe aim of this investigation is to consistently incorporate quantum corrections in the transport model for applications to nanoscale semiconductor devices. This paper is made of two parts. In Part I, a set of two semiclassical equations were derived, in which the dynamics of the dispersion of the single-particle wave function is accounted for in addition to that of the expectation value of position. The model is founded on an approximate description of the wave function that eliminates the need for the Ehrenfest approximation. This leads to a set of two Newton-like single-particle equations for position and dispersion. Here, in Part II, it is shown that the Lagrangian form of the single-particle equations naturally lends itself to the incorporation of such extended dynamics into the statistical framework. The theory is suitable for different levels of applications: description of the single-particle ballistic dynamics, solution of the generalized Boltzmann equation by Monte Carlo or other methods, and solution of the continuity equations in the position-dispersion space
TFET Inverters With n-/p-Devices on the Same Technology Platform for Low-Voltage/Low-Power Applications
No full textThis paper investigates feasible inverter configurations based on co-optimized n- and p-type tunnel field-effect transistors (TFETs) integrated on the same InAs/Al0.05Ga0.95Sb platform. Based on 3-D full-quantum simulations, the considered devices feature steep subthreshold slopes and relatively high on- currents and are combined into two inverter designs. Benchmarking against aggressively scaled CMOS logic based on multigate architectures highlights potential of the proposed TFET implementations to perform up to 10 × and 100× faster in low operating power and low standby power environments, respectively. The comparison is conducted at low supply voltages (VDD =0.25 V) and for equal levels of static power consumption. The proposed TFET-based platform is thus expected to be a good candidate for low-voltage/low-power applications in near-future technology generations
Contact-induced negative differential resistance in short-channel graphene FETs
No full textIn this paper, we clarify the physical mechanism for the phenomenon of negative output differential resistance (NDR) in short-channel graphene FETs through nonequilibrium Green's function simulations and a simpler semianalytical ballistic model that captures the essential physics. This NDR phenomenon is due to a transport mode bottleneck effect induced by the graphene Dirac point in the different device regions, including the contacts. NDR is found to occur only when the gate biasing produces an n-p-n or p-n-p polarity configuration along the channel, for both positive and negative drain-source voltage sweep. In addition, we also explore the impact on the NDR effect of contact-induced energy broadening in the source and drain regions and a finite contact resistance. © 1963-2012 IEEE
A Coherent Extension of the Transport Equations in Semiconductors Incorporating the Quantum Correction: Part I – Single Particle Dynamics
No full textThe aim of the investigation is to consistently incorporate quantum corrections in the transport model for applications to nanoscale semiconductor devices. This paper is comprised of two parts. Part I derives a set of two semiclassical equations in which the dynamics of the dispersion of the single-particle wave function is accounted for in addition to that of the expectation value of position. The model is founded on an approximate description of the wave function that eliminates the need of the Ehrenfest approximation. This leads to a set of two Newton-like single-particle equations for position and dispersion. In Part II, it will be shown that the Lagrangian form of the single-particle equations naturally lends itself to the incorporation of such extended dynamics into the statistical framework. The theory is suitable for different levels of applications: description of the single-particle ballistic dynamics, solution of the generalized Boltzmann equation by the Monte Carlo method or other methods, and solution of the continuity equations in the position-dispersion space
Design guidelines for GaSb/InAs TFET exploiting strain and device size
No full textA simulation study exploring the possibility of performance improvements for GaSb/InAs nanowire TFETs under appropriate stress conditions is carried out. It is demonstrated that biaxial tensile strain induces a remarkable enhancement of the on-state current thanks to bandgap reduction; however, a degradation of the ambipolar behavior is observed as well. Some stress intensity values and device geometry configurations are investigated. The best simulated device can achieve an on/off current ratio of about 3×107 with ION≈0.33 mA/μm at VDD=0.3 V
Optimization of staggered heterojunction p-TFETs for LSTP and LOP applications
No full textEffect of transverse quantization on the broken vs. staggered band lineup of InAs/Al(x)Ga(1-x)Sb TFETs is investigated, showing that cross-sections up to 10nm lead to staggered configurations for any value of the Al mole fraction x. Device performance is optimized as a function of cross-sectional size, Al content and possible source/channel underlap, while ensuring low standby power (LSTP) or low operating power (LOP) compatible off-current levels. Guidelines are provided and an “optimal” design is proposed which provides a minimum sub-threshold slope (SS) of 7.2 mV/dec along with a maximum on-state current (Ion) of 175μA/μm
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