Theory of Carbon-Vacancy Diffusion at the SiO2/4H-SiC Interface

2019 ◽  
Vol 963 ◽  
pp. 204-207
Author(s):  
Hind Alsnani ◽  
J.P. Goss ◽  
Patrick R. Briddon ◽  
Mark J. Rayson ◽  
Alton B. Horsfall
Keyword(s):  
Field Effect ◽  
Density Functional ◽  
Carrier Lifetime ◽  
Field Effect Transistors ◽  
Active Regions ◽  
Vacancy Diffusion ◽  
Functional Theory ◽  
Native Defects ◽  
Carbon Vacancy ◽  
Defects And Impurities

Experimental data indicate that carbon vacancies incorporated in active regions of SiC devices are important electrical defects, responsible for device limiting effects such as carrier lifetime reduction. For field-effect transistors that include a 4H-SiC/SiO2 interface, such as at the gate, the oxidation pro- cess is understood to introduce native defects to the SiC, including injection of carbon self-interstitials and vacancies, that diffuse into the active layer and interact with other defects and impurities. It is therefore important to understand the migration behaviour of primary native defects such as VC in the vicinity of 4H-SiC/SiO2 interfaces. We report here the results of a density-functional theory investi- gation into the diffusion of the carbon vacancy in such a region. We conclude that the migration of VC is significantly hindered in the immediate vicinity of the interface, with the energy of diffusion barrier being approximately 15% greater than the corresponding diffusion in bulk 4H-SiC.

ATOMISTIC SIMULATION OF GATE EFFECT ON NANOSCALE INTRINSIC Si FIELD-EFFECT TRANSISTORS

2009 ◽  
Vol 08 (01n02) ◽  
pp. 113-117 ◽  
Author(s):  
X. F. WANG ◽  
L. N. ZHAO ◽  
Z. H. YAO ◽  
Z. F. HOU ◽  
M. YEE ◽  
...  
Keyword(s):  
Field Effect ◽  
Density Functional ◽  
Field Effect Transistors ◽  
Functional Theory ◽  
Poisson Solver ◽  
System A ◽  
Voltage Curve ◽  
Gate Effect ◽  
Multigrid Poisson Solver ◽  
Model Device

We study the electrostatic and quantum transport properties of nanoscale double-gated Si -based field effect transistors within the framework of density functional theory combined with nonequilibrium Green's function approach. In our model device system, a Si slab is sandwiched between two insulator slabs and connected to two semi-infinite Si electrodes at its left and right ends. The effect of the double gates is taken into account by applying proper electrostatic boundary conditions and solving the Poisson equation self-consistently in the system. In the representation of localized SIESTA linear combination of atomic orbitals, the study is carried out with the help of Atomistix ToolKit (ATK) package together with an efficient multigrid Poisson solver. We find that the surface potential versus gate voltage curve shows similar characteristics as in conventional MOSFETs even for devices of 1 nm size, though the shape of the curve varies with the shrink of the system. In different working regimes of the devices, the electrostatic potential and the transmission spectrum are analyzed for an atomistic understanding of the device behavior.

Organic Field-Effect Transistors Based on 3’-Flouro-2,2',6,6'-Tetraphenyl-4,4'-Dipyranylidene

2019 ◽  
Vol 288 ◽  
pp. 37-43
Author(s):  
Altan Bolag ◽  
Yoshiro Yamashita
Keyword(s):  
Field Effect ◽  
Density Functional ◽  
Field Effect Transistors ◽  
Organic Field Effect Transistors ◽  
X Ray Diffraction ◽  
Si Substrate ◽  
Visible Spectroscopy ◽  
Functional Theory ◽  
X Ray ◽  
Contact Configuration

In this work, 3’-flouro-2,2',6,6'-tetraphenyl-4,4'-dipyranylidene (3FDP) was originally synthesized and investigated with density functional theory (DFT) calculations, ultraviolet–visible spectroscopy (UV–Vis) and cyclic voltammetry (CV) in comparison with 2,2',6,6'-tetraphenyl-4,4'-dipyranylidene (DP) and 4’-flouro-2,2',6,6'-tetraphenyl-4,4'-dipyranylidene (4FDP). 3FDP-based organic field-effect transistors (OFETs) were fabricated with bottom contact configuration on bare SiO2/Si substrate, 1,1,1,3,3,3-hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (OTS) treated substrate, respectively. The HMDS-treated device showed highest mobility of 4 × 10−4 cm2 V−1 s−1, on/off ratio of 4 × 103 and threshold voltage of −10 V. Finally, vacuum deposited 3FDP films morphology was investigated by X-ray diffraction (XRD) analyses and the results showed higher crystallinity of HMDS-treated 3FDP film compared to the OTS-treated film, leading to a better FET performance.

Ab initio performance predictions of single-layer In–V tunnel field-effect transistors

2017 ◽  
Vol 19 (30) ◽  
pp. 20121-20126 ◽  
Author(s):  
Juan Lu ◽  
Zhi-Qiang Fan ◽  
Jian Gong ◽  
Xiang-Wei Jiang
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Field Effect ◽  
Density Functional ◽  
Field Effect Transistors ◽  
Single Layer ◽  
Functional Theory ◽  
Performance Predictions ◽  
P Type

The device performances of both n-type and p-type tunnel field-effect transistors (TFETs) made of single-layer InX (X = N, P, As, Sb) are theoretically evaluated through density functional theory (DFT) and ab initio simulations in this paper.

Enhancement of tunneling current in phosphorene tunnel field effect transistors by surface defects

2018 ◽  
Vol 20 (8) ◽  
pp. 5699-5707 ◽  
Author(s):  
Juan Lu ◽  
Zhi-Qiang Fan ◽  
Jian Gong ◽  
Jie-Zhi Chen ◽  
Huhe ManduLa ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Transport Properties ◽  
Field Effect ◽  
Density Functional ◽  
Surface Defects ◽  
Field Effect Transistors ◽  
Tunneling Current ◽  
Functional Theory ◽  
Non Equilibrium Green’S Function ◽  
Nitrogen Phosphorus

The effects of the staggered double vacancies, hydrogen (H), 3d transition metals, for example cobalt, and semiconductor covalent atoms, for example, germanium, nitrogen, phosphorus (P) and silicon adsorption on the transport properties of monolayer phosphorene were studied using density functional theory and non-equilibrium Green's function formalism.

scholarly journals Raman investigation of electric field induced molecular modifications in organic field effect transistors

ELEMENTOS ◽  
2013 ◽  
Vol 2 (2) ◽  
Author(s):  
Beynor Antonio Paez Sierra ◽  
Fredy Giovanni Mesa Rodríguez
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Field Effect ◽  
Density Functional ◽  
Field Effect Transistors ◽  
Dipole Interaction ◽  
Original Structure ◽  
Organic Layer ◽  
Organic Field Effect Transistors ◽  
Functional Theory

The influence of external electric fields on the vibrational properties of Pentacene-based field effect transistors were investigated by Ramanspectroscopy.ThemonitoredRamanbandswereintherangefrom 1100cm−1 to1200cm−1,whereabroadbandispresentandenhanceddue to the external electric field. The process is modeled by density functional theory (DFT) at the B3LYP/3–21G level. Additionally, the relaxation of the Raman bands after the removal of the external field was determined from an exponential Debye like decay fitting to be approximately 94 min, this finding indicates that a long relaxation time ca. 8 h is required in order to recover the original structure. Experimentally and theoretically was demonstrated that the applied electric fields induce artificial traps in the organic layer mediated by charge carrier–dipole interaction.

scholarly journals Native Defects and their Doping Response in the Lithium Solid Electrolyte Li7La3Zr2O12

2019 ◽  
Author(s):  
Alex Squires ◽  
David Scanlon ◽  
Benjamin Morgan
Keyword(s):  
Density Functional ◽  
Ionic Conductivities ◽  
Density Functional Theory Calculations ◽  
Defect Chemistry ◽  
Functional Theory ◽  
Native Defects ◽  
Synthesis Conditions ◽  
Reducing Conditions ◽  
Solid State Batteries ◽  
Hybrid Density Functional

<p>The Li-stuffed garnets Li<sub><i>x</i></sub>M<sub>2</sub>M<sub>3</sub>′O<sub>12</sub> are promising Li-ion solid electrolytes with potential use in solid-state batteries. One strategy for optimising ionic conductivities in these materials is to tune lithium stoichiometries through aliovalent doping, which is often assumed to produce proportionate numbers of charge compensating Li vacancies. The native defect chemistry of the Li-stuffed garnets, and their response to doping, however, are not well understood, and it is unknown to what degree a simple vacancy-compensation model is valid. Here, we report hybrid density-functional–theory calculations of a broad range of native defects in the prototypical Li-garnet Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub>. We calculate equilibrium defect concentrations as a function of synthesis conditions, and model the response of these defect populations to extrinsic doping. We predict a rich defect chemistry that includes Li and O vacancies and interstitials, and significant numbers of cation-antisite defects. Under reducing conditions, O vacancies act as colour-centres by trapping electrons. We find that supervalent (donor) doping does not produce charge compensating Li vacancies under all synthesis conditions; under Li-rich / Zr-poor conditions the dominant compensating defects are Li<sub>Zr</sub> antisites, and Li stoichiometries strongly deviate from those predicted by simple “vacancy compensation” models.<br></p>

Sign in / Sign up

Export Citation Format

Share Document