V. S. Lysenko

Carrier transport in amorphous SiC/crystalline silicon heterojunctions

Charge carrier transport in chemical vapor-deposited amorphous SiC/p-type crystalline Si heterostructures has been studied over the temperature range 80–400 K, using current–voltage (I–V), current–temperature (I–T), capacitance–voltage (C–V), and capacitance relaxation (C–t) characteristics. These heterojunctions exhibit high breakdown voltages (230 V) and a diode rectification ratio of 103 at ±0.5 V. At low temperatures (80–120 K) the a-SiC behaves like a dielectric, and the interface built-in voltage can be determined from the capacitance–voltage plot. The corresponding low forward bias current flow is limited by variable-range electron hopping conductivity at Fermi level in the a-SiC layer. At increasing temperature and forward bias voltage, an additional hole current component is found with the transport governed by a multistep tunneling hole emission process through the a-SiC/c-Si heterobarrier. At still higher forward bias voltages (>0.8 V), space-charge-limited hole conduction in the presence of tr...

Kinetics of structural and phase transformations in thin SiOx films in the course of a rapid thermal annealing

Infrared spectroscopy and analysis of photoluminescence spectra have been used to study variations in the composition of the oxide phase in a SiOx film and the precipitation of the Si phase in the course of a rapid thermal annealing for 1–40 s at temperatures of 500–1000°C. Kinetics of phase segregation has been observed for the first time at temperatures of 600–700°C: an increase in the amount of precipitated silicon as the annealing duration increases followed by an eventual leveling off. The phase separation is brought to completion in a time as short as 1 s at temperatures higher than 900°C. The diffusion coefficient is estimated in the context of a model of the diffusion-controlled formation of Si nanoparticles. The obtained values of the diffusion coefficient exceed, by five to ten orders of magnitude, those of the silicon diffusion coefficients in SiO2 and Si and are comparable to the diffusion coefficients of the oxygen contained in these structures. It is assumed that oxygen mobility forms the basis for the mechanism of structural and phase transformations in the SiOx layers and for the formation of Si nanoparticles in the course of annealing.

Study of the processes of carbonization and oxidation of porous silicon by Raman and IR spectroscopy

Porous silicon layers were produced by electrochemical etching of single-crystal silicon wafers with the resistivity 10 Ω cm in the aqueous-alcohol solution of hydrofluoric acid. Raman spectroscopy and infrared absorption spectroscopy are used to study the processes of interaction of porous silicon with undiluted acetylene at low temperatures and the processes of oxidation of carbonized porous silicon by water vapors. It is established that, even at the temperature 550°C, the silicon-carbon bonds are formed at the pore surface and the graphite-like carbon condensate emerges. It is shown that the carbon condensate inhibits oxidation of porous silicon by water vapors and contributes to quenching of white photoluminescence in the oxidized carbonized porous silicon nanocomposite layer.

Hydrogen effect on enhancement of defect reactions in semiconductors: example for silicon and vacancy defects

Abstract A model of interaction of the hydrogenated vacancy with silicon interstitial and different dopants (B, P and As) in crystalline silicon is considered. Quantum chemical calculations show that hydrogenation of the vacancy leads to a decrease of mechanical stresses of the silicon crystalline lattice near vacancy and consequently to a considerable decrease of the energy barrier height for the interstitial atom incorporation into the vacancy site of the crystalline lattice. The potential barriers for incorporation of the interstitial into the site and for leaving the atoms from the site have been calculated as a function of hydrogen localization in the vicinity of the vacancy (inside and outside of the vacancy), the charge state of hydrogen localized outside the vacancy (H 0 and H + ), and the transport direction (〈111〉, 〈110〉 and 〈100〉) of the atoms both in and out of the vacancy. The theory is compared with the experimental results.

Enhanced activation of implanted phosphorus in silicon under rf plasma treatment

Abstract Photoluminescence of bound excitons is used to study the process of phosphorus activation in surface layers of implanted AlSiO2Si structures under rf nitrogen plasma treatment. It is shown that nonthermal process of phosphorus activation takes place at rf plasma treatment of silicon.

Electrical Characterization and Parameter Extraction of Junctionless Nanowire Transistors

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.

Relaxation of amorphous structure of implanted Si under RF plasma treatment: Raman and EPR study

The Raman spectroscopy method is used to study the influence of thermal and RF plasma treatment on the structure of near-surface Si layers in Si-SiO2 structures implanted with P+ ions. Thermal annealing at T=500 degrees C is found to bring about an insignificant increase in microcrystalline dimensions and a small change in the root mean square bond angle deviation Delta theta . At T>500 degrees C, a jump-type transition from the amorphous state to the crystalline one occurs. The treatment in the RF plasma discharge in nitrogen atmosphere when increasing power density up to 2.0 W cm-2 leads to the increase in the microcrystalline average dimensions from 35 AA up to 90 AA and the decrease in the value of Delta theta . At P>1.2 W cm-2, the value of Delta theta =6.8 degrees , which is very close to the minimum possible value of Delta theta min=6.6 degrees . This indicates a practically full relaxation of Si amorphous structure. A complete correlation of Raman data with changes in paramagnetic defect concentration in the amorphous structure (D0 centres, g=2.0055), established by the EPR method, was obtained.

The Effect of Incorporation of Hydrocarbon Groups on Visible Photoluminescence of Thermally Treated Fumed Silica

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.

The influence of vacuum annealing temperature on the fundamental absorption edge and structural relaxation of a-SiC:H films

The effect of vacuum annealing temperature on the characteristics of the fundamental absorption edge and short-range order reconstruction in amorphous hydrogenated silicon carbide (a-SiC:H) films obtained by magnetron sputtering of silicon in an Ar/CH4 mixture is experimentally investigated. It is shown that redistribution of chemically bound hydrogen occurs at low annealing temperatures (450°C). This redistribution is determined by (i) breakage of silicon-hydrogen bonds and (ii) trapping of atomic hydrogen by carbon dangling bonds. These processes lead to an enhancement of visible photoluminescence. Breakage of carbon-hydrogen bonds and clusterization of amorphous carbon occur at higher annealing temperatures. The proposition that the main nonradiative recombination centers in a-SiC:H films are electronic states related to the carbon dangling bonds is justified.

Quantum chemical investigations of atomic hydrogen effect on Frenkel pairs annihilation in silicon

The SCF MO LCAO method in the valence approach with neglect of diatomic differential overlap (NDDO) is used to study the effect of atomic hydrogen on the silicon lattice relaxation in the nearest vicinity of a vacancy. It is shown that hydrogen atoms are localized mainly as second-nearest neighbours of the vacancies on the Si - Si bond, which results in a significant extension of the vacancy region. The potential barrier height and its dependence on the vacancy charge state were calculated for Frenkel pair annihilation with a hydrogenated vacancy in the cases of hydrogen localization inside and outside the vacancy. The results substantiate a model of enhanced annihilation of Frenkel pairs in hydrogenated crystalline Si.