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Backgating effect in GaAs FETs with a channel–semi-insulating substrate boundary

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Journal of Semiconductors 2014年第3期35卷 33-38页

作者： Ahmed Chaouki Megherbi said benramache Abderrazak Guettaf Electrical Engineering Department Faculty of Technology University of Biskra Material Sciences Department Faculty of Sciences University of Biskra

This study focuses on modeling the effects of deep hole traps, mainly the effect of the substrate（backgating effect） in a GaAs transistor MESFT. This effect is explained by the existence, at the interface, of a space charge zone. Any modulation in this area leads to response levels trapping the holes therein to the operating temperature. We subsequently developed a model treating the channel substrate interface as an N–P junction, allowing us to deduce the time dependence of the component parameters of the total resistance R ds, the pinch-off voltage V P, channel resistance, fully open R co and the parasitic series resistance R S to bind the effect trap holes H1and H0. When compared with the experimental results, the values of the R DS（t S/ model for both traps show that there is an agreement between theory and experiment; it has inferred parameter traps, namely the density and the time constant of the trap. This means that a space charge region exists at the channel–substrate interface and that the properties can be approximated to an N–P junction.

关键词： traps pinch-off voltage resistance channel substrate interface

Surface morphology and electrochemical characterization of electrodeposited Ni-Mo nanocomposites as cathodes for hydrogen evolution

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Chinese Physics B 2015年第10期24卷 559-563页

作者： Elhachmi Guettaf Temam Hachemi Ben Temam said benramache Laboratoire de Physique des Couches Minces et Applications Université de Biskra

In this work, we study the influences of current density on surface morphology and electrochemical characterization of electrodeposited Ni-Mo. The Ni-Mo composite coatings are deposited on pretreated copper substrates by electrolytic deposition. The Ni-Mo solution is taken from nickel sulfate fluid and ammonium heptamolybdate with 10 g/l. The Ni-Mo composite coatings are deposited at a temperature of 303 K with an applied current density of j dep= 10 A/dm2-30 A/*** find that the corrosion resistance is improved by incorporating Mo particles into Ni matrix in 0.6-M Na Cl solution. From the potentiodynamic polarization curve of electrodeposited Ni-Mo it is confirmed that the corrosion resistance decreases with increasing applied current density. The x-ray diffraction（XRD） analyses of Ni-Mo coatings indicate three phases of Mo Ni4, Mo1.24Ni0.76, and Ni3 Mo phases crystallites of nickel and molybdenum. The scanning electronic microscopy（SEM） tests indicate that Ni-Mo coatings present cracks and pores.

关键词： Ni-Mo electrolytic deposition corrosion resistance potentiodynamic polarization plating current density

Effect of substrate temperature on the stability of transparent conducting cobalt doped ZnO thin films

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Journal of Semiconductors 2012年第9期33卷 18-21页

作者： said benramache Boubaker Benhaoua Foued Chabane Material Sciences Laboratory Faculty of ScienceUniversity of Biskra 07000Algeria Physics Laboratory Institute of TechnologyUniversity of El-oued 39000Algeria Mechanics Department Faculty of TechnologyUniversity of Biskra 07000Algeria

Transparent conducting Co doped ZnO thin films have been fabricated by Ultrasonic spray. The thin films were deposited at three different substrate temperatures of 300, 350 and 400 ℃. The obtained films had a hexagonal wurtzite structure with a strong （002） preferred orientation. The maximum crystallite size value of the film deposited at 350 ℃ is 55.46 nm. Spectrophotometer （UV-vis） of a Co doped ZnO film deposited at 350 ℃ shows an average transmittance of about 90%. The band gap energy increased from 3.351 to 3.362 eV when the substrate temperature increased from 300 to 350 ℃. The electrical conductivity of the films deposited at 300, 350 and 400 ℃ were 7.424, 7.547 and 6.743 （Ω·cm）^-1 respectively. The maximum activation energy value of the films at 350 ℃ was 1.28 eV, indicating that the films exhibit a n-type semiconducting nature.

关键词： ZnO:Co films transparent conducting films ultrasonic spray deposition substrate temperature band gap energy

The effect of the film thickness and doping content of SnO2:F thin films prepared by the ultrasonic spray method

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Journal of Semiconductors 2013年第9期34卷 21-25页

This paper reports on the effects of film thickness and doping content on the optical and electrical properties of fluorine-doped tin oxide. Tin （Ⅱ） chloride dehydrate, ammonium fluoride dehydrate, ethanol and HC1 were used as the starting materials, dopant source, solvent and stabilizer, respectively. The doped films were deposited on a glass substrate at different concentrations varying between 0 and 5 wt% using an ultrasonic spray technique. The SnO2：F thin films were deposited at a 350 ℃ pending time （5, 15, 60 and 90 s）. The average transmission was about 80%, and the films were thus transparent in the visible region. The optical energy gap of the doped films with 2.5 wt% F was found to increase from 3.47 to 3.89 eV with increasing film thickness, and increased after doping at 5 wt%. The decrease in the Urbach energy of the SnO2：F thin films indicated a decrease in the defects. The increase in the electrical conductivity of the films reached maximum values of 278.9 and 281.9 （Ω.cm）-1 for 2.5 and 5 wt% F, respectively, indicating that the films exhibited an n-type semiconducting nature. A systematic study on the influence of film thickness and doping content on the properties of SnO2：F thin films deposited by ultrasonic spray was reported.

关键词： SnO2 fluoride thin film film thickness TCO ultrasonic spray technique

Effect of band gap energy on the electrical conductivity in doped ZnO thin film

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Journal of Semiconductors 2014年第7期35卷 19-22页

作者： said benramache Okba Belahssen Hachemi Ben Temam Physic Laboratory of Thin Films and Applications LPCMA University of BiskraBiskra 07000Algeria

The transparent conductive pure and doped zinc oxide thin films with aluminum, cobalt and indium were deposited by ultrasonic spray technique on glass substrate at 350 ℃. This paper is to present a new approach to the description of correlation between electrical conductivity and optical gap energy with dopants＇ concentration of A1, Co and In. The correlation between the electrical and optical properties with doping level suggests that the electrical conductivity of the films is predominantly estimated by the band gap energy and the concentrations of A1, Co and In. The measurement in the electrical conductivity of doped films with correlation is equal to the experimental value, the error of this correlation is smaller than 13%. The minimum error value was estimated in the cobalt-doped ZnO thin films. This result indicates that such Co-doped ZnO thin films are chemically purer and have far fewer defects and less disorder owing to an almost complete chemical decomposition.

关键词： ZnO thin films semiconductor doping electrical conductivity optical gap energy correlation

The calculation of band gap energy in zinc oxide films

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Journal of Semiconductors 2015年第1期36卷 17-22页

作者： Ali Arif Okba Belahssen Salim Gareh said benramache Electrical Engineering Department Faculty of Technology University of Biskra Algeria Laboratoire de Physique des Couches Minces et Applications (LPCMA) Université de Biskra Algeria Mechanical Engineering Department Faculty of Technology University of Biskra Algeria

We investigated the optical properties of undoped zinc oxide thin films as the n-type semiconductor;the thin films were deposited at different precursor molarities by ultrasonic spray and spray pyrolysis *** thin films were deposited at different substrate temperatures ranging between 200 and 500℃. In this paper, we present a new approach to control the optical gap energy of ZnO thin films by concentration of the ZnO solution and substrate temperatures from experimental data, which were published in international journals. The model proposed to calculate the band gap energy with the Urbach energy was investigated. The relation between the experimental data and theoretical calculation suggests that the band gap energies are predominantly estimated by the Urbach energies, film transparency, and concentration of the ZnO solution and substrate temperatures. The measurements by these proposal models are in qualitative agreements with the experimental data; the correlation coefficient values were varied in the range 0.96–0.99999, indicating high quality representation of data based on Equation（2）, so that the relative errors of all calculation are smaller than 4%. Thus, one can suppose that the undoped ZnO thin films are chemically purer and have many fewer defects and less disorder owing to an almost complete chemical decomposition and contained higher optical band gap energy.

关键词： ZnO thin films semiconductor band gap energy correlation

Preparation of transparent conducting ZnO:Al films on glass substrates by ultrasonic spray technique

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Journal of Semiconductors 2013年第7期34卷 26-30页

作者： Abdelouahab Gahtar said benramache Boubaker Benhaoua Foued Chabane VTRS Laboratory Institute of TechnologyUniversity of El-oued 39000Algeria Material Sciences Department Faculty of ScienceUniversity of Biskra 07000Algeria Mechanics Department Faculty of TechnologyUniversity of BiskraBiskra 07000Algeria

Transparent conductive Al doped ZnO thin films were deposited by ultrasonic spray *** of preparation have been optimized to get good quality.A set of aluminum（Al） doped ZnO（between 0 and 5 wt%） thin films were grown on glass substrate at 350℃.Nanocrystalline films with a hexagonal wurtzite structure show a strong（002） preferred *** maximum value of grain size G = 32.05 nm is attained of Al doped ZnO film with 3 wt%.All the films have low absorbance in the visible region,thus the films are transparent in the visible region;the band gap energy increased from 3.10 to 3.26 eV when Al concentration increased from 0 to 3 wt%.The electrical conductivity of the films increased from 7.5 to 15.2（Ω·cm）^（-1）.So the best results are achieved in Al doped ZnO film with 3 wt%.

关键词： ZnO:A1 thin films TCO ultrasonic spray technique

Correlation between electrical conductivity–optical band gap energy and precursor molarities ultrasonic spray deposition of ZnO thin films

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Journal of Semiconductors 2013年第11期34卷 15-19页

作者： said benramache Okba Belahssen Abderrazak Guettaf Ali Arif Material Sciences Laboratory Faculty of Science University of Biskra Physic Laboratory of Thin Films and Applications LPCMA University of Biskra Department of Electrical Faculty of Technology University of Biskra

ZnO thin films were deposited using the simple, flexible and cost-effective spray ultrasonic technique at different precursor molarities values. The films were deposited on a glass substrate at 350℃. This paper is to present a new approach to the description of correlation between electrical conductivity and optical gap energy with precursor molarity of ZnO thin films. The ZnO films exhibit higher electrical n-type semiconductors, whose band gap energy increased from 3.08 to 3.37 eV with an increasing of precursor molarity of 0.05 to 0.1 M. The maximum value of electrical conductivity of the films is 7.96 （***）-1 obtained in the ZnO thin film for precursor molarity 0.125 M. The correlation between the electrical and the optical properties with the precursor molarity suggests that the electrical conductivity of the films is predominantly influenced by the band gap energy and the precursor molarity. The measurement of the electrical conductivity of the films with correlation is equal to the experimental with the error is about 1% in the higher conductivity.

关键词： ZnO thin films correlation electrical conductivity, ultrasonic spray technique

Structural, optical and electrical properties of zinc oxide thin films deposited by a spray pyrolysis technique

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Journal of Semiconductors 2015年第1期36卷 23-27页

作者： Yacine Aoun Boubaker Benhaoua Brahim Gasmi said benramache Mechanical Department Faculty of Technology University of Biskra Biskra 07000 Algeria VTRS Laboratory Institute of Technology University of El-Oued El-Oued 39000 Algeria Laboratoire de Physique des Couches Minces et Application University of Biskra Biskra 07000 Algeria Material Sciences Department Faculty of Science University of Biskra Biskra 07000 Algeria

Zinc oxide（ZnO） thin films were deposited on glass substrates by spray pyrolysis technique decomposition of zinc acetate dihydrate in an ethanol solution with 30 m L of deposition rate, the ZnO thin films were deposited at two different temperatures： 300 and 350℃. The substrates were heated using the solar cells *** substrate was R217102 glass, whose size was 30×17.5×1 mm^3. The films exhibit a hexagonal wurtzite structure with a strong（002） preferred orientation. The higher value of crystallite size is attained for sprayed films at 350℃, which is probably due to an improvement of the crystallinity of the films at this point. The average transmittance of obtain films is about 90%–95%, as measured by a UV–vis analyzer. The band gap energy varies from 3.265 to 3.294 e V for the deposited Zn O thin film at 300 and 350℃, respectively. The electrical resistivity measured of our films are in the order 0.36 Ω·cm.

关键词： ZnO thin films substrate temperature spray pyrolysis technique