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Article Citation - WoS: 11Citation - Scopus: 13Fabrication and Characterization of To/Gase Au) Schottky Diodes(Iop Publishing Ltd, 2006) Qasrawi, AF; Department of Electrical & Electronics EngineeringThe optical properties of amorphous GaSe thin films deposited onto tin oxide (TO) coated glass substrates are presented for the purpose of using this material for the fabrication of metal-semiconductor devices. Specifically, the room temperature direct allowed and forbidden transition energy band gaps of glass/TO and glass/TO/GaSe films are estimated and found to exhibit values of 3.95 and 1.95 eV, respectively. The temperature dependence of the energy band gap of the glass/TO/GaSe is also studied in the temperature range of 295 - 450 K by means of optical transmittance and reflectance spectra. This study allowed the identification of the rate of change of the band gap with temperature as -5.0 x 10(-4) eV K-1 and the 0 K energy band gap as 2.1 eV. The above reported optical parameters of the glass/TO/GaSe structure seem to be suitable for semiconductor device production such as solar cell converters, metal - insulator - semiconductor (MIS), metal-oxide-semiconductor (MOS), MOSFET, etc devices. As an application, we have used the glass/TO/GaSe substrate for fabricating Schottky diodes using Ag and Au point contacts. The diodes are characterized by measuring the current (I) - voltage (V) characteristics at room temperature. The I - V curves exhibit rectifying properties. The I-V data analysis in the Schottky region (below 1.0 V) revealed barrier heights of 0.60 and 0.73 eV for Ag and Au point contacts, respectively.Article Citation - WoS: 30Citation - Scopus: 30Optoelectronic and Electrical Properties of Tlgas2 Single Crystal(Wiley-v C H verlag Gmbh, 2005) Qasrawi, AF; Gasanly, NMThe optoelectronic and electrical properties of TIGaS2 single crystals have been investigated by means of room temperature transmittance and reflectance spectral analysis, Hall coefficient, dark electrical resistivity and photocurrent measurements in the temperature range of 200-350 K. The optical data have revealed an indirect and direct allowed transition band gaps of 2.45 and 2.51 eV, an oscillator and dispersion energy of 5.04 and 26.45 eV, respectively, a static dielectric constant of 6.25 and static refractive index of 2.50. The dark Hall coefficient measurements have shown that the crystals exhibit a conductivity type conversion from p-type to n-type at a critical temperature of 315 K. Deep donor and acceptor energy levels of 0.37/0.36 eV and 0.66 eV has been calculated from the temperature dependence of Hall coefficient and resistivity, and photocurrent measurements, respectively. The photocurrent decreases with decreasing temperature. The analysis of the photocurrent data have revealed that, the recombination mechanism is linear and supralinear above and below 290 K, respectively. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Article Citation - WoS: 26Citation - Scopus: 26Photoelectronic, optical and electrical properties of TlInS2 single crystals(Wiley-v C H verlag Gmbh, 2003) Qasrawi, AF; Gasanly, NMTo specify the donor energy levels in TlInS2 single crystals, the dark electrical resistivity, photoconductivity and Hall measurements were carried out in the temperature range of 100-400 K, 110-350 K and 170-400 K, respectively. The Hall measurements revealed that the crystals exhibit an anomalous behavior of Hall voltage by changing sign (from p-type to n-type conductivity) at 315 K. By means of the temperature dependence of dark electrical resistivity, Hall coefficient and photocurrent measurements the donor energy levels located at 360, 280, 152 and 112 meV were detected. The photocurrent-illumination intensity dependence follows the law I-Ph proportional to F-gamma with gamma being 1.0 (linear), 0.5 (sublinear), 1.0 (linear) and 1.3 (supralinear) at low, moderate, high and very high illumination intensities indicating the monomolecular in the bulk, bimolecular and strong recombination at the surface, respectively. The photocurrent is observed to increase with increasing temperature up to a maximum temperature (T-m) 245 K. T is observed to shift to higher temperature as F increases, and disappears in the region where I-Ph-F dependence is supralinear. The phenomenon is attributed to the exchange in the behavior of the sensitizing and recombination centers. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA. Weinheim.Article Citation - WoS: 11Citation - Scopus: 11Dispersive Optical Constants and Temperature-Dependent Band Gap of Cadmium-Doped Indium Selenide Thin Films(Iop Publishing Ltd, 2005) Qasrawi, AF; Department of Electrical & Electronics EngineeringPolycrystalline cadmium-doped indium selenide thin films were obtained by the thermal co-evaporation of alpha-In2Se3 crystals and Cd onto glass substrates kept at a temperature of 200 degrees C. The temperature dependence of the optical band gap in the temperature region of 300-450 K and the room temperature refractive index, n(lambda), of these films have been investigated. The absorption edge shifts to lower energy as temperature increases. The fundamental absorption edge corresponds to a direct energy gap that exhibits a temperature coefficient of -6.14 x 10(-4) eV K-1. The room temperature n(lambda) which was calculated from the transmittance data allowed the identification of the oscillator strength and energy, static and lattice dielectric constants and static refractive index as 20.06 and 3.07 eV, 7.43 and 10.52 and 2.74, respectively.Article Citation - WoS: 16Citation - Scopus: 17Investigation of Localized Levels in Gas0.5se0.5< Layered Crystals by Means of Electrical, Space-Charge Limited Current and Photoconductivity Measurements(Wiley-v C H verlag Gmbh, 2002) Qasrawi, AF; Gasanly, NMTo identify the localized levels in GaS0.5Se0.5 single crystals, the dark electrical conductivity, current-voltage characteristics and photoconductivity measurements were carried out in the temperature range of 250-400 K. Temperature dependence of dark electrical conductivity and the space-charge limited current studies indicate the presence of a single discrete trapping level located at 0.31 eV below the conduction band with a density of about 1.3 x 10(15) cm(-3). The conductivity data above 320 K reveal an additional donor level with activation energy of 0.40 eV indicating the extrinsic nature of conduction. The spectral distribution of photocurrent in the photon energy range of 0.65-5.9 eV reveals an indirect band gap of 2.26 eV. The photocurrent-illumination intensity dependence follows the law I-ph proportional to F-gamma, with gamma being 1.0, 0.65, and 0.5 at low, moderate and high illumination intensities, respectively. The corresponding behavior indicates the domination of monomolecular recombination, near equal densities of trapped and recombination centers and bimolecular recombination. It is observed that the photocurrent increases in the temperature range from 250 K up to T-m = 360 K and decreases for T > T-m. The temperature dependence of the photocurrent reveals two additional impurity levels with activation energies of 0.14 and 0.10 eV below and above Tm, respectively.Article Citation - WoS: 13Citation - Scopus: 13Light Illumination Effect on the Electrical and Photovoltaic Properties of In6s7< Crystals(Iop Publishing Ltd, 2006) Qasrawi, AF; Gasanly, NMThe electrical and photoelectrical properties of In6S7 crystals have been investigated in the temperature regions of 170-300 K and 150-300 K, respectively. The dark electrical analysis revealed the intrinsic type of conduction. The energy band gap obtained from the temperature-dependent dark current is found to be 0.75 eV. It is observed that the photocurrent increases in the temperature range of 150 K up to T-m = 230 K and decreases at T > T-m. Two photoconductivity activation energies of 0.21 and 0.10 eV were determined for the temperature ranges below and above Tm, respectively. The photocurrent (I-ph)-illumination intensity (F) dependence follows the law I-ph alpha F-gamma. The value of. decreases when the temperature is raised to T-m, then it starts increasing. The change in the value. with temperature is attributed to the exchange in role between the recombination and trapping centres in the crystal. The crystals are found to exhibit photovoltaic properties. The photovoltage is recorded as a function of illumination intensity at room temperature. The maximum open-circuit voltage and short-circuit photocurrent density, which are related to an illumination intensity equivalent to one sun, are 0.12 V and 0.38 mA cm(-2), respectively.Article Citation - WoS: 18Citation - Scopus: 18Growth, Electrical and Structural Characterization of Β-Gase Thin Films(Springer, 2003) Parlak, M; Qasrawi, AF; Erçelebi, ÇGaSe thin films were deposited onto the glass substrates kept at 200degrees and 300degreesC by the thermal evaporation of GaSe crystals under the pressure of 10(-5) Torr. X-ray analysis of the films revealed that films grown at 200. C are amorphous in nature while the films grown at 300degreesC are polycrystalline beta-GaSe. The temperature dependent electrical conductivity measurements in the region of 320-100 K for the films grown at 300degreesC showed that the transport mechanisms are the thermionic emission of charged carriers and the variable range hopping above and below 180 K, respectively. Space charge limited current (SCLC) studies have also been performed on these films through the current-voltage measurements at different temperatures and a dominant hole trap at 0.233 eV from the top of the valance band with a trap density of similar to1.6 x 10(11) cm(-3) is identified. (C) 2003 Kluwer Academic Publishers.Article Citation - WoS: 20Citation - Scopus: 20Characterization of P-in2se3< Thin Films(Kluwer Academic Publ, 2001) Qasrawi, AF; Parlak, M; Erçelebi, Ç; Günal, IIndium selenide thin films were deposited onto glass substrates kept at 150 degreesC by thermal evaporation of alpha -In2Se3. Some of the films were annealed at 150 degreesC and 200 degreesC and they all were found to exhibit p-type conductivity without intentional doping. Scanning electron microscopy (SEM) established that the films have an atomic content of In51Se49. X-ray diffraction (XRD) indicated that the as-grown films were amorphous in nature and became polycrystalline \beta-In2Se3 films after annealing. The analysis of conductivity temperature-dependence measurements in the range 320-100 K revealed that thermal excitation and thermionic emission of the carriers are the predominant conduction mechanisms above 200 K in the amorphous and polycrystalline samples, respectively. The carrier transport below 200 K is due to variable range hopping in all the samples. Hall measurements revealed that the mobility of the polycrystalline films is limited by the scattering of the charged carriers through the grain boundaries above 200 K. (C) 2001 Kluwer Academic Publishers.Article Citation - WoS: 25Citation - Scopus: 25Temperature Effect on Dark Electrical Conductivity, Hall Coefficient, Space Charge Limited Current and Photoconductivity of Tlgas2 Single Crystals(Iop Publishing Ltd, 2005) Qasrawi, AF; Gasanly, NMThe dark electrical conductivity, Hall coefficient, space charge limited current, and illumination and temperature dependences of the photocurrent of TIGaS2 single crystals in the temperature regions of 100-350, 200-350, 200-290 and 100-350 K, respectively, have been measured and analysed. The Hall coefficient measurements revealed the extrinsic type of conduction with conductivity-type conversion from p- to n-type at a critical temperature of 315 K. The temperature dependence of the dark electrical conductivity exhibits activation behaviour with activation energies (0.360 +/- 0.005) eV and (0.240 +/- 0.005) eV at high and low temperatures, respectively. The space charge limited current analysis has shown that the energy level of (0.240 +/- 0.005) eV is a trapping state with trap density of (2.2-3.9) x 10(12) cm(-3). The data analysis of the photocurrent-temperature dependence has revealed two photoconductivity activation energies of (0.660 +/- 0.005) eV and (0.360 +/- 0.005) eV in the temperature regions of 290-350 K and 220-280 K, respectively. The illumination dependence of photoconductivity is found to exhibit linear and supralinear recombination mechanisms above and below 290 K, respectively.Article Citation - WoS: 8Citation - Scopus: 8Photoelectronic and Electrical Properties of Ins Crystals(Iop Publishing Ltd, 2002) Qasrawi, AF; Gasanly, NMTo identify the localized levels in InS single crystals, the dark electrical conductivity, current-voltage characteristics and photoconductivity measurements were carried out in the temperature range of 10-350 K. Temperature dependence of dark electrical conductivity and the space-charge limited current studies indicate the presence of a single discrete trapping level located at (10 +/- 2) meV below the conduction band with a density of about 4.8 x 10(11) cm(-3). The conductivity data above 110 K reveal an additional two independent donor levels with activation energies of (50 +/- 2) and (164 +/- 4) meV indicating the extrinsic nature of conductivity. The spectral distribution of photocurrent in the photon energy range of 0.8-3.1 eV reveals an indirect band gap of (1.91 +/- 0.04) eV. The photocurrent-illumination intensity dependence follows the law I-ph proportional to F-gamma, with gamma being 1.0 and 0.5 at low and high illumination intensities indicating the domination of monomolecular and bimolecular recombination, respectively. It is observed that the photocurrent increases in the temperature range of 10 K up to T-m = 110 K and decreases or remains constant for 110 K < T < 160 K and increases again above 160 K. The temperature dependence of the photocurrent reveals an additional shallow impurity level with activation energies of 3 meV.
