Abstract: In this work, an overview is given on the prospects and challenges of two novel device concepts,namely the Tunnel FET (TFET) and the Superlattice FET (SL-FET). The optimization effort ofhomo- and hetero-junction TFETs carried out so far shows that these devices can provide an advantageover CMOS FETs only for very-low power and low-performance niche applications, so long asthe supply voltage is scaled below 300 mV. The required materials for homojunction TFETs are lowbandgap semiconductors, such as InAs and InGaAs; for heterojunction TFETs the best semiconductorpair appears to be (Al)GaSb-InAs. Several technological problems are still unsolved: poor qualityof the oxide interface with III-V materials and device variability are probably the most important. The SL-FET represents in principle a better device concept, as it provides outstanding performance and meets nearly all targets of the high performance (HP), low operating power (LOP) and low standby power (LSTP) of the ITRS at VDD = 0.4V. A suitably-designedInGaAs-InAlAs SL-FET has turned out to provide the best simulation results. However, the fabricationprocess of SL-FETs is much more complex, as it requires molecular epitaxy to deposit multiplelayers with a very strict control of their nanometric thickness. Besides, vertical devices can poseunexpected problems as far as layout organization and parasitics are concerned.
Abstract: This article presents a review of various methods for extracting the key parameters of junctionless (JL) MOSFETs, namely, the threshold voltage, flat-band voltage, doping concentration, carrier mobility, and parasitic series resistance. The applicability and limitations of different methods are analyzed using numerical simulations and experimental data for planar and tri-gate nanowire JL transistors with various nanowire widths.
Abstract: The electron spin properties of semiconductors are of immense interest for their potential in spin-driven applications. Silicon is a perfect material for spintronics due to a long spin lifetime. Understanding the peculiarities of the subband structure and details of spin propagation in thin silicon films in the presence of the spin-orbit interaction is under scrutiny. We have performed simulations to obtain the surface roughness limited, acoustic-and optical-phonon mediated spin relaxation time, when the film is under shear strain. The degeneracy between the non-equivalent valleys is lifted by strain, which in turn subdues the dominating inter-valley relaxation components and increases the spin lifetime. We also elaborate on the injection orientation sensitive spin relaxation model and predict that the spin relaxation time is maximum, when the spin is injected in-plane, relative to the (001) oriented silicon film.
Abstract: Study the magnetic properties of Si<B,Ni> whiskers, the concentration of which corresponds to a dielectric and metal side of metal-insulator transition, is performed. Percolation laws of the magnetic clusters formation, that is important for development of spintronic devices, are considered.
Abstract: In this work, fabrication and characterisation of graphene photodiodes and transfer length method structures is presented. Graphene growth is carried out using a thermal chemical vapor deposition process on copper foils and subsequently transferred onto silicon-dioxide/silicon substrate. Comparison of electrical and optical characteristics of the photodiodes, which are fabricated on both n-type and p-type silicon, is shown. The photodiodes fabricated on n-type silicon show good rectifying behaviour when compared with photodiodes fabricated on p-type silicon. Spectral response of graphene photodiodes is measured to be less than 0.2 mAW-1 which is attributed to the light absorbance of 2.3% for single layer graphene. Transfer length method device structures are also fabricated and contact resistance is calculated and plotted as a function of spacing between the contacts. The calculated contact resistance (RcW) is 0.87 kΩ.µm. The latter structures are also characterised under various ambient conditions, before and after annealing. The value of contact resistance reduces from 0.87 kΩ.µm to 0.75 kΩ.µm after annealing. This reduction is attributed to the improvement in bonding between graphene and metal. Measurements under vacuum show an increase in contact resistance which is attributed to the removal of adsorbed water molecules on the surface on graphene. The sheet resistivity of graphene is calculated to be between 1.17 kΩ/□ and 3.67 kΩ/□.
Abstract: In this article photoelectric phenomena taking place in the MOS system will be discussed and the classical theory of these phenomena will be presented. This will be followed by pointing out some shortcomings of this theory and presentation of our contributions which eliminate these shortcomings and allow development of new MOS system characterization methods.
Abstract: Methyl, methoxy and alcoxy groups with different number of carbon atoms were chemically grafted onto the surface of fumed silica nanoparticles. After chemical modification the nanopowders were annealed in vacuum at 700 °C. The effect of the amount of carbon atoms in grafted hydrocarbon groups and type of bonding to silica surface (Si-C v.s. Si-O-C) were studied. It was demonstrated that carbon incorporation results in the development of broad band photoluminescence that covers the wholevisible spectral range. Increasing of carbon incorporation resulted in increasing of photoluminescence intensity and red shift of the photoluminescence band maximum.
Abstract: The paper deals with obtaining of textured silicon surfaces by chemical etching. As a result of experiments based on the modification and optimization of obtaining a textured silicon, several methods of chemical texturing of the crystalline silicon surface were developed. It was shown that modified isotropic and anisotropic etching methods are applicable to create a microrelief on the surface of silicon substrate. These methods in addition to their high conversion efficiency can be used for both mono- and multicrystalline silicon which would ensure their industrial use.
Abstract: Processes of e-beam and holographic recording of surface-relief structures using Ge5As37S58–Se multilayer nanostructures as registering media were studied in this paper. Optical properties of Ge5As37S58, Se layers and Ge5As37S58–Se multilayer nanostructures were investigated. Spectral dependencies of refractive index were analyzed within the frames of single-oscillator model. Values of optical band gaps for Ge5As37S58, Se layers and Ge5As37S58–Se multilayer nanostructures were obtained from Tauc dependencies. Holographic recording process depends on the polarization of the recording beams. Using e-beam and holographic recording diffraction gratings and other elements were recorded in Ge5As37S58–Se multilayer nanostructures.