Variability in Si nanowire MOSFETs due to the combined effect of interface roughness and random dopants: a fully three-dimensional NEGF simulation study

Martinez, A., Seoane, N., Brown, A.R., Barker, J.R. and Asenov, A. (2010) Variability in Si nanowire MOSFETs due to the combined effect of interface roughness and random dopants: a fully three-dimensional NEGF simulation study. IEEE Transactions on Electron Devices, 57(7), pp. 1626-1635. (doi: 10.1109/TED.2010.2048405)

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In this paper, we study the impact of surface roughness and its combination with random discrete dopants on the current variability in nanometer-scale nanowire metal-oxide-semiconductor field-effect transistors. It is shown that these two variability sources cannot be regarded as independent in their effect on transport. Interface roughness results in body thickness fluctuations and scattering, which degrades transistor performance. This paper extends our previous study, in which we concentrated only on the impact of random discrete dopants in the source/drain regions in the same type of devices that lead to current variability. We have simulated ensembles of 30 devices, which differ due to the physical manifestation of the variability sources, including the detailed microscopic pattern of the interface in the channel and the number and configuration of discrete dopants in the source/drain regions. An ensemble of devices, with rough interfaces and continuous doping, has first been simulated to differentiate the effect of the interface roughness from the random discrete dopants before considering the combined case. It was found that, in some peculiar cases, the surface roughness induced resonant structures inside the device, producing quasi-bound states. These resonant states are similar to those related to individual discrete dopants in our previous study. We found that there is strong correlation between the microscopic patterns of the interface and the device performance due to the non-self-averaging of the microscopic features, which plagues devices with small channel lengths. The surface roughness induces a threshold voltage shift and decreases the ON-current of the device due to scattering. In the fully 3-D nonequilibrium Green's function formalism, both effects are combined in the propagation of the electron wave through the device. We have extracted the surface roughness related scattering contribution and estimated the associated mobility

Item Type:Articles
Keywords:channel device devices Discrete random dopants ELECTRON-PHONON INTERACTIONS field-effect transistors fluctuations impact IMPURITY INTERFERENCE INVERSION LAYER MOBILITY mobility MOSFET MOSFETS non equilibrium green functions performance QUANTUM-TRANSPORT random dopants resonances SCATTERING si silicon nanowire FET simulation SURFACE surface roughness surface-roughness threshold transistor transistors UNIVERSALITY variability
Glasgow Author(s) Enlighten ID:Barker, Professor John and Asenov, Professor Asen and Brown, Mr Andrew and Martinez, Dr Antonio
Authors: Martinez, A., Seoane, N., Brown, A.R., Barker, J.R., and Asenov, A.
College/School:College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
Journal Name:IEEE Transactions on Electron Devices
Publisher:Institute of Electrical and Electronics Engineers
ISSN (Online):1557-9646
Published Online:21 June 2010

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
443791Atomic scale simulation of nanoelectronic devicesAsen AsenovEngineering & Physical Sciences Research Council (EPSRC)EP/E038344/1Electronic and Nanoscale Engineering