Papers by basudev nag chowdhury
The current work investigates the performance of dual-gate GaAs-nanowire FET as a chargequbit dev... more The current work investigates the performance of dual-gate GaAs-nanowire FET as a chargequbit device operating at room temperature. In compatibility with the state-of-the-art classical bit technology, it is shown that the single gate of a nanowire FET can be replaced by two localized gates to achieve such charge-qubit operation. On application of relevant biases to the localized gates, two voltage tunable quantum dots are created within the nanowire channel with electrostatically controlled single-state-occupancy and inter-dot coupling leading to charge-qubit operation at room temperature. The associated electron transport is theoretically modeled on the basis of non-equilibrium Green’s function (NEGF) formalism. The ‘initialization’ and ‘manipulation’ for qubit operation are performed by applying suitable gate voltages, whereas the ‘measurement’ is executed by applying a small drain bias to obtain a pulse current of ~pA order. A ~25 MHz frequency of coherent oscillation is observed...
The present work theoretically investigates the probability of generation of entangled electron-p... more The present work theoretically investigates the probability of generation of entangled electron-photon pair in high-energy Compton scattering of unpolarized electrons and photons due to scattering-channel-exchange mechanism. The study suggests that the scattering of unpolarized electrons and photons with nearly equal energy of the order of MeV at cross-channel can create entangled pair of up-spin electron and RCP photon or down-spin electron and LCP photon. The entanglement is quite strong exhibiting jump-concurrence for particular directions of scattering however not limited by the Kapitza-Dirac restriction. Such strong electron-photon entanglement is observed to be highly selective along the directions of scattering on the surface of two opposite cones at 45 degree around the electron-detector axis and on the plane perpendicular to it, the latter one exhibiting maximal entanglement. The work predicts that spin-polarization entangled electron-photon pairs are highly possible to be ...
Quantum Information Processing, 2021
The present work theoretically investigates the probability of generation of entangled electron-p... more The present work theoretically investigates the probability of generation of entangled electron-photon pair in high-energy Compton scattering of unpolarized electrons and photons due to scattering-channel-exchange mechanism. The study suggests that the scattering of unpolarized electrons and photons with nearly equal energy of the order of MeV at cross-channel can create entangled pair of up-spin electron and RCP photon or down-spin electron and LCP photon. The entanglement is quite strong exhibiting jump-concurrence for particular directions of scattering, however not limited by the Kapitza-Dirac restriction. Such strong electron-photon entanglement is observed to be highly selective along the directions of scattering on the surface of two opposite cones at 45° around the electron-detector axis and on the plane perpendicular to it, the latter one exhibiting maximal entanglement. The work predicts that spin-polarization entangled electron-photon pairs are highly possible to be found in practical experiments of high-energy Compton scattering with specific directional selectivity.
Design and Modeling of High-Efficiency GaAs -Nanowire Metal-Oxide-Semiconductor Solar Cells beyond the Shockley-Queisser Limit: An NEGF Approach
Physical review applied, 2021
The present work proposes a $\mathrm{Ga}\mathrm{As}$-nanowire-based vertical metal-oxide-semicond... more The present work proposes a $\mathrm{Ga}\mathrm{As}$-nanowire-based vertical metal-oxide-semiconductor (MOS) solar cell of quantum scale to achieve very high efficiency beyond the Shockley-Queisser (SQ) limit. Photogeneration and carrier transport in such devices are analytically modeled by adopting nonequilibrium Green's function formalism based on second quantization field operators for the incident photons and generated photocarriers. The study suggests that the utilization of photogenerated light and heavy holes to harvest solar energy is capable of providing significantly higher power conversion efficiency above the SQ limit. Such superior efficiency is achieved due to the resonance of incident photon modes with the energy gap between three-dimensional-quantized electron states and two-dimensional-quantized hole subbands. The power conversion efficiency, along with other relevant solar-cell-performance parameters, such as open-circuit voltage, short-circuit current, fill fa...
Designing InP-Nanowire Based Vertical Metal-Oxide-Semiconductor Capacitors for Wavelength Selective Visible Light Sensing
Springer Proceedings in Physics, 2019
The current work investigates photogeneration phenomena in InP-nanowire vertical metal-oxide-semi... more The current work investigates photogeneration phenomena in InP-nanowire vertical metal-oxide-semiconductor (MOS) photo-capacitor by developing a theoretical model with second quantization description of photon absorption by a self-consistent simultaneous quantum-electrostatic solver. The equations are solved by using non-equilibrium Green’s function (NEGF) formalism. The vertical MOS device can directly detect the color of incident light in the range of 380–700 nm (visible region) with high spectral resolution by varying the nanowire diameter and applied voltage. The entire visible spectrum is detected with relatively higher device dimensions in comparison to the Si-nanowire based device. Such devices can be a potential candidate for wavelength selective direct photodetection with lesser fabrication complexities.
Analytical Modeling of Vertically Oriented Standalone Si-Nanowire Metal-Oxide-Semiconductor Capacitors for Wavelength Selective Near-Infrared Sensing Applications
In the current work, photogeneration in a vertically oriented standalone Si-nanowire metal-oxide-... more In the current work, photogeneration in a vertically oriented standalone Si-nanowire metal-oxide-semiconductor (MOS) capacitor has been investigated by developing a theoretical model that incorporates phase-breaking phenomena such as electron-photon interaction. For this purpose, a set of quantum field equations associated with second quantization electron and photon field operators have been solved through non-equilibrium Green’s function (NEGF) formalism by achieving self-consistency with Poisson’s equation. The obtained photocapacitance profile shows sharp peaks at specific wavelengths, detected by their relevant diameter-voltage combinations in the near-infrared region. Such peaks are observed to be shifted towards shorter wavelengths with increasing the applied voltage. Thus, the proposed device scheme can contribute significantly to wavelength selective photosensing applications with high selectivity.
Chapter 4 * Electrical characterization of single standalone n-ZnO nanowire / pSi heterojunction diode 4
The sustained progress of ZnO based nano-electronics research demands an extensive investigation ... more The sustained progress of ZnO based nano-electronics research demands an extensive investigation of both the physical and electrical behavior of single nanowires for developing the comprehensive understanding to bring such devices into circuit level applications. Moreover, the development of ZnO nanowire based single active devices such as switches and rectifiers are essential prior to the fabrication of nanoelectronic circuits and components [262,263]. Therefore, the control over fabrication and characterization of such elements on a single nanowire is crucial since such nanostructure circuit components are the integration of several individual nanowire based devices. The fabrication of reliable and superior nanodevices with ZnO nanowires is only possible when the properties of such single nanowire are investigated adequately. In this context, the ZnO (0 0 2) nanowires are grown on p-Si (1 0 0) substrate by employing double-step Sol-gel/CBD technique. The grown ZnO nanowires are in...
Energy band-structure estimation of semiconductor nanotubes with consideration of momentum space quantization
In the current work, the effect of quantum confinement in the band structure of semiconductor nan... more In the current work, the effect of quantum confinement in the band structure of semiconductor nanotubes is investigated. The confinement of electrons in the momentum space is incorporated in sp3s∗ model to determine band structure of the nanotubes. The spherically symmetric r-point of nanotube energy bands is observed to split into cylindrically symmetric r′ and spherically symmetric r″ points due to confinement in transverse directions. Such splitting of r-point leads to increase the band gap ofnanotubes which further increases to a large extent with the decrease of nanotube core diameter and wall thickness. Such semiconductor nanotubes exhibit novel properties which can be exploited for developing novel quantum electronic devices.
Physical Review Applied, 2021
A diagrammatic approach of impedimetric phase angle-modulus sensing for identification and quantification of various polar and non-polar/ionic adulterants in milk
LWT, 2021
Abstract The current article demonstrates a novel diagrammatic approach for the detection and qua... more Abstract The current article demonstrates a novel diagrammatic approach for the detection and quantification of polar and non-polar/ionic adulterants in milk by employing electrical impedance spectroscopy (EIS). For such study, some commonly used milk adulterants including melamine, starch, urea, allantoin, cyanuric acid, benzoic acid, ammonium sulphate and sodium bicarbonate are incorporated in a controlled manner in the pure milk sample. The presence of such adulterants in milk is confirmed by Fourier transform mid-infrared (FT-MIR) spectroscopy prior to impedimetric measurements. A Pt/Teflon/SiO2/Si biosensor device is fabricated for EIS measurement where the combination of SiO2 and Teflon layer thicknesses are optimized to obtain an appropriate hydrophobicity/dielectricity for the liquid milk samples. The EIS study shows an opposite trend in the variation of electrical impedance, capacitance and conductance for the polar samples in comparison to non-polar/ionic adulterants, upon their controlled addition from 0.5 to 9 (mg/g). Such results are utilized for detection and quantification of the milk-adulterants by developing a diagrammatic approach based on impedimetric phase angle-modulus mapping. Such diagrammatic impedance spectroscopy provides a generic scheme for a rapid, cost-effective and point-of-care detection and quantification of adulterants in milk which can be further extended to other bio-consumables.
Band splitting induced by momentum-quantization in semiconductor nanostructures: Observation of emission lines in Indium Phosphide (InP) nanotubes
Physics Letters A, 2021
Abstract Two spectral emission lines originated from band splitting in Indium Phosphide nanotubes... more Abstract Two spectral emission lines originated from band splitting in Indium Phosphide nanotubes are observed experimentally. The nanotubes are grown by Metal-Organic Chemical Vapour Deposition on patterned template developed by electron beam lithography. The splitting effect arising from spatial confinement-induced momentum quantization on the band structure of nanotubes is investigated by developing a theoretical model. The incorporation of momentum quantization in sp3s*-model with spin-orbit coupling indicates the splitting of Γ-point into two different symmetric points, which emit two spectral lines as confirmed by cathodoluminescence spectra. The observation provides novel insight into the band structure based transport behaviour of semiconductor quantum devices.
Catalyst-modified Vapor-Liquid-Solid (VLS) Growth of Single Crystalline β-Gallium Oxide (Ga2O3) Thin Film on Si-Substrate
Superlattices and Microstructures, 2019
Abstract In the current work, a single crystalline β-Gallium Oxide (Ga2O3) thin film (~15 nm) is ... more Abstract In the current work, a single crystalline β-Gallium Oxide (Ga2O3) thin film (~15 nm) is grown on Si-substrate by employing catalyst-modified vapor-liquid-solid (VLS) method. The FESEM and AFM images indicate the formation of a continuous film with small surface roughness. XRD measurement confirms the formation of a highly crystalline 1 ¯ 11 >-plane of β-phase of Ga2O3. The chemical states and optical properties of such films are analyzed by X-ray photoelectron spectroscopy (XPS) and Spectroscopic ellipsometry (SE). The energy bandgap, refractive index and extinction coefficient of the grown β-Ga2O3 film are obtained to be 4.78 eV, 1.84 and 0.10, respectively. The vacancies/defect states are studied from Photoluminescence (PL) spectra where the major PL-peaks corroborate with the transitional energy values obtained from SE measurement. Therefore, the study suggests that the VLS method, amongst the state-of-the-art growth techniques, is capable of growing high-quality single crystalline β-Ga2O3 thin film in a relatively simple and cost-effective approach.
Understanding the electrostatics of top-electrode vertical quantized Si nanowire metal–insulator–semiconductor (MIS) structures for future nanoelectronic applications
Journal of Computational Electronics, 2019
In this paper, a comprehensive analysis of the electrostatics of top-electrode vertically aligned... more In this paper, a comprehensive analysis of the electrostatics of top-electrode vertically aligned quantized Si nanowire metal–insulator–semiconductor (MIS) structure is performed by formulating a self-consistent analytical model with simultaneous solution of Schrodinger and Poisson equations. The impact of high-k dielectrics on the electrostatic control of such quantized nanowire MIS devices is studied in detail. The electrostatic control is observed to degrade significantly for such high-k insulators with identical equivalent oxide thickness (EOT) due to the nonlinear dependence between dielectric constant and EOT in quantized nanowire MIS devices. The distribution of 3D confined charges along the nanowire is primarily governed by the generated quantum states which are a nonlinear function of the applied voltage. The electrostatic integrity of such device is investigated in terms of simultaneously maintaining the electrostatic control and reduction in carrier tunneling probability. In this context, the impact of several controlling parameters such as applied voltage, barrier height of the insulator/semiconductor junction, carrier effective mass of the insulator and nanowire diameter on tunneling probability is examined. The results suggest insulator effective mass (high-m*) to be the more significant parameter for maintaining electrostatic integrity than its dielectric constant (high-k) in quantized nanowire top-electrode MIS devices.
Ultrathin Vapor–Liquid–Solid Grown Titanium Dioxide-II Film on Bulk GaAs Substrates for Advanced Metal–Oxide–Semiconductor Device Applications
IEEE Transactions on Electron Devices, 2018
In this paper, a high-quality crystalline thin film (~10 nm) of titanium dioxide (TiO<sub>2... more In this paper, a high-quality crystalline thin film (~10 nm) of titanium dioxide (TiO<sub>2</sub>-II) phase is grown on p-GaAs <inline-formula> <tex-math notation="LaTeX">$\langle 100\rangle $ </tex-math></inline-formula> substrate by employing the vapor–liquid–solid method. The formation of crystalline TiO<sub>2</sub>-II films is confirmed by X-ray diffraction study. A very small rms surface roughness of ~1 nm has been measured from atomic force microscopy. The capacitance–voltage characteristics of Al/TiO<sub>2</sub>-II/GaAs metal–oxide–semiconductor (MOS) capacitor indicate the growth of excellent thin film of TiO<sub>2</sub>-II phase with high effective dielectric constant of 28, 35, 65, and 14 for the as-grown and 600 °C, 625 °C, and 650 °C annealed samples, respectively. An effective oxide thickness of ~0.7 nm, a negligible hysteresis of 10 mV, very small frequency dispersion of 3.5%, and a reduced gate leakage current of ~10<sup>−13</sup> A/<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}^{\textsf {2}}$ </tex-math></inline-formula> at +2 V are achieved due to annealing in the temperature range of 600 °C–625 °C. Thus, this paper provides a cost-effective novel alternative technique to grow high-quality TiO<sub>2</sub>-II films on GaAs substrate which may be used as the reliable high-<inline-formula> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> gate dielectrics on III–V semiconductor-based MOS devices and circuits.
Formation of High-Pressure Phase of Titanium Dioxide (TiO2 -II) Thin Films by Vapor-Liquid-Solid Growth Process on GaAs Substrate
physica status solidi (a), 2018
Analytical modeling to design the vertically aligned Si-nanowire metal-oxide-semiconductor photosensors for direct color sensing with high spectral resolution
Physica E: Low-dimensional Systems and Nanostructures, 2017
Abstract In the current work, an analytical model for the design of vertically aligned silicon (S... more Abstract In the current work, an analytical model for the design of vertically aligned silicon (Si) nanowire metal-oxide-semiconductor (MOS) capacitor based multi-color photodetectors has been developed for the detection of entire visible spectrum with high spectral resolution. The photogeneration phenomena within the nanostructures are analyzed in detail by developing a quantum field model associated with second quantization electron-photon field operators. The non-equilibrium Green's function (NEGF) formalism is employed to solve the relevant equations. The study shows that the proposed device with specified design of diameter-voltage combinations is capable of detecting 64 spectral bands of the entire visible spectrum (380 nm to700 nm) directly with a very high resolution of 5 nm wavelength. Such direct sensing of each wavelength is observed to be independent of the fluctuations of illumination intensity. The device is designed to obtain a full-width-at-half-maximum (FWHM) smaller than the spectral resolution (5 nm) for each wavelength of the visible range, which indicates a very high quality digital imaging/sensing method. Such devices may be a potential alternative for the future nanoelectronics based photodevices for superior sensing/imaging applications.
Unusual impact of electron-phonon scattering in Si nanowire field-effect-transistors: A possible route for energy harvesting
Superlattices and Microstructures, 2016
Abstract In the current work, the impact of electron-phonon scattering phenomena on the transport... more Abstract In the current work, the impact of electron-phonon scattering phenomena on the transport behaviour of silicon nanowire field-effect-transistors with sub-mean free path channel length has been investigated by developing a theoretical model that incorporates the responses of carrier effective mass mismatch between the channel and source/drain. For this purpose, a set of relevant quantum field equations has been solved by non-equilibrium Green's function formalism. The obtained device current for a particular set of biases is found to decrease due to phonon scattering below a certain doping level of source/drain, above which it is observed to enhance anomalously. Analyses of the quantified scattering lifetime and power dissipation at various confinement modes of the device indicates that such unusual enhancement of current is originated from the power served by phonons instead of associated decay processes. The power generation has been observed to improve by using high-k materials as gate insulator. Such results may contribute significantly to the future nano-electronic applications for energy harvesting.
Selective strain incorporation and retention into Si-substrate through VLS growth of TiO2 nano-islands
Materials Research Express, 2017
In this work, process induced strain has been incorporated selectively into Si-substrate by growi... more In this work, process induced strain has been incorporated selectively into Si-substrate by growing TiO2 nano-islands on it using vapour–liquid–solid method and the induced strain has been retained by chemically removing the TiO2 nano-islands. The retained strain is quantified by employing pole study method of the electron backscatter diffraction (EBSD) and compared with the similar results obtained from micro-Raman measurements. A very good agreement between the results indicates accuracy of the developed pole study analyses. Both the methods suggest that such a low-cost approach is capable of incorporating and retaining a compressive strain >4.7% along and tensile strain >1.3% along and directions by growing the crystalline TiO2 nano-islands on Si substrates followed by their chemical removal.
Modeling of transport behavior of the ballistic Silicon nanowire gate-all-around field-effect-transistors (Si NWFETs) with Si/SiO<inf>2</inf> interface roughness
2012 5th International Conference on Computers and Devices for Communication (CODEC), 2012
ABSTRACT In the current work, the contribution of gate oxide/channel interface roughness has been... more ABSTRACT In the current work, the contribution of gate oxide/channel interface roughness has been estimated and incorporated into the transport models of a Si nanowire field-effect-transistor (Si NWFET). This has been incorporated by modifying the relevant energy sub-bands taking into account the roughness in both transverse and longitudinal directions. Accordingly, the channel Hamiltonian matrix elements related to energy sub-bands are modified. It has been observed from the study that such interface roughness has significant effect on the device performance in terms of transfer and output characteristics. The transfer characteristics show that the current decreases up to 40% for an increase in interface roughness up to 25%.
Investigation of the Role of Aspect Ratio for the Design of Si-Nanowire Field-Effect-Transistors in Ballistic Regime
Nanoscience and Nanotechnology Letters, 2013
ABSTRACT In the current work, the impact of aspect ratio (Channel diameter/Channel length = D/L) ... more ABSTRACT In the current work, the impact of aspect ratio (Channel diameter/Channel length = D/L) on the performance parameters of ballistic Si nanowire field-effect-transistors (Si-NWFETs) is studied. Key device parameters of the NWFET such as on-current to off-current ratio (I on/I off), threshold voltage (Vth ), sub-threshold swing (SS), and drain induced barrier lowering (DIBL) are found to vary significantly with its aspect ratio. The nanowire MOSFETs exhibit an operation analogous to enhancement type for D/L &lt; 0.31 and to achieve a sub-100 mV threshold voltage, an aspect ratio &gt;0.2 is required. I on/I off ratio of the order of 104 and, SS and DIBL, as small as 60 mV/dec and 20 mV/V, respectively, are obtained for the aspect ratio ≤0.2.
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Papers by basudev nag chowdhury