Impact Of Quantum Mechanical Effects Research Articles

Impact of quantum confinement on transport and the electrostatic driven performance of silicon nanowire transistors at the scaling limit

In this work we investigate the impact of quantum mechanical effects on the device performance of n-type silicon nanowire transistors (NWT) for possible future CMOS applications at the scaling limit. For the purpose of this paper, we created Si NWTs with two channel crystallographic orientations 〈110〉 and 〈100〉 and six different cross-section profiles. In the first part, we study the impact of quantum corrections on the gate capacitance and mobile charge in the channel. The mobile charge to gate capacitance ratio, which is an indicator of the intrinsic performance of the NWTs, is also investigated. The influence of the rotating of the NWTs cross-sectional geometry by 90° on charge distribution in the channel is also studied. We compare the correlation between the charge profile in the channel and cross-sectional dimension for circular transistor with four different cross-sections diameters: 5nm, 6nm, 7nm and 8nm. In the second part of this paper, we expand the computational study by including different gate lengths for some of the Si NWTs. As a result, we establish a correlation between the mobile charge distribution in the channel and the gate capacitance, drain-induced barrier lowering (DIBL) and the subthreshold slope (SS). All calculations are based on a quantum mechanical description of the mobile charge distribution in the channel. This description is based on the solution of the Schrödinger equation in NWT cross sections along the current path, which is mandatory for nanowires with such ultra-scale dimensions.

QUANTUM SIMULATIONS OF DUAL GATE MOSFET DEVICES: BUILDING AND DEPLOYING COMMUNITY NANOTECHNOLOGY SOFTWARE TOOLS ON NANOHUB.ORG

Undesirable short-channel effects associated with the relentless downscaling of conventional CMOS devices have led to the emergence of new classes of MOSFETs. This has led to new and unprecedented challenges in computational nanoelectronics. The device sizes have already reached the level of tens of nanometers where quantum nature of charge-carriers dominates the device operation and performance. The goal of this paper is to describe an on-going initiative on nanoHUB.org to provide new models, algorithms, approaches, and a comprehensive suite of freely-available web-based simulation tools for nanoscale devices with capabilities not yet available commercially. Three software packages nanoFET, nanoMOS and QuaMC are benchmarked in the simulation of a widely-studied high-performance novel MOSFET device. The impact of quantum mechanical effects on the device properties is elucidated and key design issues are suggested.

Effects of inversion layer quantization on channel profile engineering for nMOSFETs with 0.1 μm channel lengths

This paper presents a systematic theoretical investigation of the effects of inversion layer quantization on the performance of nMOSFET devices fabricated with different shapes of channel doping profiles. The bulk nMOSFET simulation structures of effective channel length near 0.1 μm were generated with gate oxide thickness of 3 nm. Abrupt- and graded-retrograde profiles with low surface and high substrate concentrations, and conventional step profiles with high surface and low substrate concentrations were used for channel doping. A hydrodynamic model for semiconductors was used to simulate various device characteristics with and without the quantum mechanical effects in the inversion layer of the devices. The simulation results indicate that the increase in the threshold voltage due to quantum mechanical effects in the inversion layer of the devices and the resulting degradation in the current drivability, drain-induced barrier lowering, and subthreshold slope depend on the shape of the channel doping profiles. The devices with retrograde channel doping profiles provide a superior control of the device performance and the shift in the device performance due to quantum mechanical effects than the devices with step channel doping profiles. It is shown that for nano-MOSFET devices, the impact of quantum mechanical effects and the variation in the device performance due to dopant fluctuations can be optimized by channel profile engineering. The paper, also, demonstrates the importance of QM effects for predictive device simulation.