Artigos
URI permanente para esta coleçãohttps://repositorio.fei.edu.br/handle/FEI/798
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Resultados da Pesquisa
- Junctionless nanowire transistors parameters extraction based on drain current measurements(2019) Trevisoli R.; Doria R.T.; de Souza M.; Barraud S.; Pavanello M.A.© 2019 Elsevier LtdThe aim of this work is to propose and qualify a systematic method for parameters extraction of Junctionless Nanowire Transistors (JNTs) based on drain current measurements and compact modeling. As junctionless devices present a different conduction mechanism than inversion-mode transistors, the methods developed for the latter devices either are not compatible or cannot be directly applied to JNTs before a deep analysis on their applicability. The current work analyzes the extraction of the series resistance, including a discussion about the influence of the first and second order mobility degradation factors, flatband voltage and low field mobility in junctionless transistors based only on static drain current curves. An analysis of the method accuracy considering the influence of the channel length, nanowire width and height, gate oxide thickness and doping concentration is also presented for devices with different characteristics through three-dimensional numerical simulations. The inclusion of the second order effects in a drain current model is also shown, considering the extracted values. The method applicability is also successfully demonstrated in experimental devices.
- Analysis of the substrate bias effect on the interface trapped charges in junctionless nanowire transistors through low-frequency noise characterization(2017) Doria R.T.; Trevisoli R.; de Souza M.; Barraud S.; Vinet M.; Faynot O.; Pavanello M.A.© 2017 Elsevier B.V.This work presents, for the first time, an experimental analysis of the low-frequency noise and the effective trap density dependence of junctionless nanowire transistors (JNTs) on the substrate bias. The study has been performed for devices with different channel lengths and doping concentrations biased close to the threshold and deep in linear regime. It has been shown that the surface potential of JNTs is strongly influenced by the substrate bias even above threshold. Thus, the drain current noise spectral density and the effective trap density can be improved or degraded depending on the bias applied to the substrate of the devices. Additionally, it is shown that, the variation on the substrate bias enables the evaluation of traps with different activation energy ranges, which is more evident in heavier doped devices due to the higher threshold voltage sensitivity to the substrate bias.
- Analytical model for the dynamic behavior of triple-gate junctionless nanowire transistors(2016) Trevisoli R.; Doria R.T.; De Souza M.; Barraud S.; Vinet M.; Pavanello M.A.© 2015 IEEE.This paper presents an analytical model for the intrinsic capacitances and transconductances of triple-gate junctionless nanowire transistors. The model is based on a surface-potential drain current model, which includes shortchannel effects, and accounts for the dependences on the device dimensions, doping concentration, and quantum effects. It is validated with 3-D Technology Computer-Aided Design (TCAD) simulations for several device characteristics and biases as well as with the experimental results.
- On the improvement of DC analog characteristics of FD SOI transistors by using asymmetric self-cascode configuration(2016) De Souza M.; Flandre D.; Doria R.T.; Trevisoli R.; Pavanello M.A.© 2015 Elsevier Ltd. All rights reserved.This paper demonstrates the improvement of DC analog performance of FD SOI transistors provided by the adoption of asymmetric self-cascode (A-SC) configuration. It consists of two transistors connected in series with gates shortened, acting as a single device. The doping concentration of the two transistors in the structure is different, leading to higher threshold voltage of the transistor at the source side of the composite structure than that of the transistor at the drain side. By reducing the doping concentration level at the channel of the transistor at drain side of the composite structure, forcing it to work in saturation, part of the applied drain bias is absorbed and does not reach the transistor close to the source, which is the main responsible for the overall device characteristics. As a result, larger drain current level and transconductance are obtained in comparison to symmetric self-cascode (where both transistors present same doping level) apart from promoting output conductance reduction. The transconductance, output conductance, Early voltage, and intrinsic voltage gain are used as figures of merit to demonstrate and validate the advantages of the proposed structure. The influence of channel length and doping concentration are also evaluated. The A-SC configuration is fully compatible with any standard FD SOI MOSFET technology with multiple threshold voltages. A simulation analysis demonstrates the feasibility of the proposed asymmetric structure in a UTBB FD SOI technology.
- Low-frequency noise and effective trap density of short channel p- and n-types junctionless nanowire transistors(2014) Doria R.T.; Trevisoli R.; De Souza M.; Pavanello M.A.This work presents an evaluation of the Low-Frequency Noise (LFN) exhibited by short-channel Junctionless Nanowire Transistors (JNTs). Unlike in previous works in which only the noise of n-type transistors was evaluated, this paper exhibits an analysis of both the LFN and the effective trap density of n- and p-type JNTs. The low-frequency noise is analyzed in terms of the channel length as well as doping concentration and has shown to be nearly independent on the former parameter when the device is biased above threshold and to decrease with the raise of the latter. Also, carrier number fluctuations dominate the LFN in nMOS JNTs whereas an important mobility fluctuation component is present in the pMOS ones. The effective trap density of JNTs has shown to be in the order of 1019 cm-3 eV-1, presenting its maximum around 1.4 nm away from the silicon/gate dielectric interface independently on the device type or doping concentration. © 2014 Elsevier Ltd. All rights reserved.
- Cryogenic operation of junctionless nanowire transistors(2011) De Souza M.; Pavanello M.A.; Trevisoli R.D.; Doria R.T.; Colinge J.-P.This letter presents the properties of nMOS junctionless nanowire transistors (JNTs) under cryogenic operation. Experimental results of drain current, subthreshold slope, maximum transconductance at low electric field, and threshold voltage, as well as its variation with temperature, are presented. Unlike in classical devices, the drain current of JNTs decreases when temperature is lowered, although the maximum transconductance increases when the temperature is lowered down to 125 K. An analytical model for the threshold voltage is proposed to explain the influence of nanowire width and doping concentration on its variation with temperature. It is shown that the wider the nanowire or the lower the doping concentration, the higher the threshold voltage variation with temperature. © 2011 IEEE.
- Threshold voltage in junctionless nanowire transistors(2011) Trevisoli R.D.; Doria R.T.; De Souza M.; Pavanello M.A.This work presents a physically based analytical model for the threshold voltage in junctionless nanowire transistors (JNTs). The model is based on the solution of the two-dimensional Poisson equation and includes the dependence on JNT width, height and doping concentration. The quantum confinement has also been taken into consideration in the model formulation. The model is validated using experimental results of nMOS and pMOS JNTs, and three-dimensional TCAD simulations where the nanowire width and height, doping concentration, gate oxide thickness and temperature have been varied. The gate oxide capacitance is also addressed aiming to adequately calculate the capacitance in non-planar devices. The temperature influence on the threshold voltage of JNTs is also analyzed. The presented model shows excellent agreement with both experimental and simulated data, adequately describing the JNT threshold voltage. © 2011 IOP Publishing Ltd.