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Article Citation - WoS: 7Citation - Scopus: 7Design of the Zns/Ge pn Interfaces as Plasmonic, Photovoltaic and Microwave Band Stop Filters(Elsevier Science Bv, 2017) Alharbi, S. R.; Qasrawi, A. F.In the current work, we report and discuss the features of the design of a ZnS (300 nm)/Ge (300 nm)/GaSe (300 nm) thin film device. The device is characterized by the X-ray diffraction, electron microscopy, energy dispersive X-ray spectroscopy (EDS), optical spectroscopy, microwave power spectroscopy and light power dependent photoconductivity. While the X-ray diffraction technique revealed a polycrystalline ZnS coated with two amorphous layers of Ge and GaSe, the hot probe tests revealed the formation of pn interface. The optical spectra which were employed to reveal the conduction and valence band offsets at the ZnS/Ge and Ge/GaSe interface indicated information about the dielectric dispersion at the interface. The dielectric spectra of the ZnS/Ge/GaSe heterojunction which was modeled assuming the domination of surface plasmon interactions through the films revealed a pronounced increase in the drift mobility of free carriers in the three layers compared to the single and double layers. In the scope of the fitting parameters, a wave trap that exhibit filtering properties at notch frequency of 2.30 GHz was designed and tested. The ac signals power spectrum absorption reached similar to 99%. In addition, the photocurrent analysis on the ZnS/Ge/GaSe interface has shown it is suitability for photovoltaic and photosensing applications. (C) 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND licenseArticle Citation - WoS: 2Citation - Scopus: 2Characterization of the Mgo/Gase0.5< Heterojunction Designed for Visible Light Communications(Elsevier Sci Ltd, 2015) Qasrawi, A. F.; AlGarni, S. E.; Gasanly, N. M.In this study an optoelectronic design is reported and characterized. The device is made of p-type MgO solved in sodium silicate binder and n-type GaSe0.5S0.5 heterojunction. It is described by means of X-ray diffraction, optical absorption and reflection in the incident light wavelength range of 190-1100 nm and by means of dark and 406 nm laser excited current (I)-voltage (V) characteristics. The optical reflectance was also measured as a function of angle of incidence of light in the range of 35-80. The structural analysis revealed no change in the existing phases of the device composers. In addition, it was observed that for pure sodium silicate and for a 67% content of MgO solved in sodium silicate binder (33%), the heterojunction exhibits a valence band shift of 0.40 and 0.70 eV, respectively. The painting of MgO improved the light absorbability significantly. On the other hand, the angle-dependent reflectance measurements on the crystal displayed a Brewster condition at 70. The MgO/ GaSe0.5S0.5 heterojunction exhibited no Brewster condition when irradiated from the MgO side. Moreover, for the crystal and the MgO/ GaSe0.5S0.5 heterojunction, the dielectric spectral analysis revealed a pronounced increase in the quality factor of the device. The I-V characteristics of the device revealed typical optoelectronic properties with high photo-response that could amplify the dark current 24 times when irradiated with 5 mW power laser light. The structural, optical, dielectric and electrical features of the MgO/GaSe0.5S0.5 heterojunction nominate it for use in visible light communication technology. (C) 2015 Elsevier Ltd. All rights reserved.Article Citation - WoS: 9Citation - Scopus: 8Dielectric dispersion in InSe/CdS bilayers(Elsevier Science Bv, 2018) Qasrawi, A. F.; Shehada, Sufyan R.In the current study, the effect of the amorphous InSe thin film substrate on the structural, optical and dielectric properties of CdS are investigated. The structural analysis of the bilayers indicated a strained growth of CdS onto InSe leading to decrease in grain size and increase in the dislocation density. The optical measurements have shown that the InSe/CdS exhibits two direct allowed transitions energy band gap values of 2.04 and 1.38 eV, in the high and low absorption regions, respectively. On the other hand, the detailed analysis of the dielectric spectra for the InSe, CdS and InSe/CdS layers has shown that the presence of the InSe substrate significantly improves the optical conduction parameters. Particularly, the Drude-Lorentz modeling for these dielectric systems revealed a drift mobility value of 329 cm(2)/V for the InSe/CdS bilayer. The deposition of the CdS onto InSe is also observed to shift the plasmon frequency of CdS from 2.49 to 0.77 GHz. The general features of the InSe/ CdS as plasmon cavities are promising as it shows its usability for production of optoelectronic devices that exhibit high performance at very high frequencies.Article Citation - WoS: 5Citation - Scopus: 5Optical Characterization of Cuin5s8< Crystals by Ellipsometry Measurements(Pergamon-elsevier Science Ltd, 2016) Isik, Mehmet; Gasanly, NizamiOptical properties of CuIn5S8 crystals grown by Bridgman method were investigated by ellipsometry measurements. Spectral dependence of optical parameters; real and imaginary parts of the pseudodielectric function, pseudorefractive index, pseudoextinction coefficient, reflectivity and absorption coefficients were obtained from the analysis of ellipsometry experiments performed in the 1.2-6.2 eV spectral region. Analysis of spectral dependence of the absorption coefficient revealed the existence of direct band gap transitions with energy 1.53 eV. Wemple-DiDomenico and Spitzer-Fan models were used to find the oscillator energy, dispersion energy, zero-frequency refractive index and high-frequency dielectric constant values. Structural properties of the CuIn5S8 crystals were investigated using X-ray diffraction and energy dispersive spectroscopy analysis. (C) 2015 Elsevier Ltd. All rights reserved.Article Citation - WoS: 3Citation - Scopus: 3Optical Analysis of Ge/Mgo and Ge/Bn Thin Layers Designed for Terahertz Applications(Elsevier Sci Ltd, 2015) Al Garni, S. E.; Qasrawi, A. F.In this work, a 200 nm Ge thin film is used as a substrate to design Ge/MgO and Ge/BN layers. The optical dynamics in these devices are investigated by means of the reflectivity and the transmissivity measurements. Particularly, the details of the dielectric spectra and the values of the energy band gaps (E-g) are investigated. Below 350 THz, the construction of Ge/MgO and Ge/BN interfaces decreased the effective dielectric constant of Ge by 39% and by 76%, respectively. It also increased the quality factor of the Ge optical device from 150 to 1400 and to 940 at 300 THz. All the dispersive optical parameters are also evaluated. In addition, the direct/indirect E-g value of Ge which was determined as 1.15/0.72 eV is observed to shift down by a 0.13/0.42 and by a 023/0.54 eV for the Ge/MgO and Ge/BN devices, respectively. The sharp increase in the dielectric constant with decreasing frequency in the range of 353 273 THz, the dispersive optical parameters and the energy band gap attenuations of the optical structures are promising as they indicate the applicability of the Ge, Ge/MgO and Gel BN layers in terahertz sensing. The latter technology has a wide range of applications like medical and telecommunication devices. (C) 2014 Elsevier Ltd. All rights reserved.Article Citation - WoS: 21Citation - Scopus: 21Design and Applications of Yb/Ga2< Schottky Barriers(Ieee-inst Electrical Electronics Engineers inc, 2017) Khanfar, Hazem K.; Qasrawı, Atef Fayez Hasan; Qasrawi, Atef F.; Zakarneh, Yasmeen A.; Gasanly, N. M.; Qasrawı, Atef Fayez Hasan; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringIn this paper, the Ga2Se3 crystals are used to design a Yb/Ga2Se3/C Schottky barrier. The device structure is investigated by the X-ray diffraction technique, which reveals a monoclinic-face-centered cubic interfacing type of structure. The barrier is studied by means of current (I)-voltage (V) characteristics in the dark and under light through photoexcitation from tungsten lamp and from the He-Ne laser. In addition, the impedance spectroscopy of these devices is studied in the frequency range of 10-1400 MHz. The photoexcited I-V curve analysis allowed investigating the biasing voltage, illumination power, and energy effects on the diode physical parameters, which are presented by the rectification ratio, the Schottky barrier height, the ideality factor, the series resistance, the photosensitivity, the responsivity, and the external quantum efficiency (EQE). While a maximum photosensitivity of 42 was observed for laser excitation with a wavelength of 632 nm at a reverse bias of 4.4 V, the EQE reached value of 1652% at 19.0 V. On the other hand, the ac current conduction analysis of the electrical conductivity, which was determined from the impedance spectral analysis, indicated that the ac signal processing through the Yb/Ga2Se3/C samples is due to the correlated hopping conduction through localized states of Fermi density of 3.98 x 10(19) eV(-1) cm(-3). The high-and biasing-dependent EQE% nominates the Yb/Ga2Se3/C as a tunable optoelectronic device.Article Citation - WoS: 2Citation - Scopus: 2Mgo/Gase0.5< Heterojunction as Photodiodes and Microwave Resonators(Ieee-inst Electrical Electronics Engineers inc, 2016) Qasrawi, Atef F.; Khanfar, Hazem K.; Gasanly, N. M.In this paper, a multifunctional operating optoelectronic device that suits visible light (VLC) and microwave communication systems is designed and characterized. The device which is composed of p-type MgO and n-type GaSe0.5S0.5 heterojunction is characterized by means of optical absorbance in the incident light energy (E) region of 3.5-1.1 eV, dark and illuminated current (I)-voltage (V) characteristics, and impedance spectra in the frequency range of 1M-1.8 GHz. Four types of lasers which generate light of wavelengths 406, 632, 850, and 1550 nm are used to excite the active region of the device. The device was also illuminated by non-monochromatic light. The incident light power was varied in the range of 1.12-10.17 mu W. It was observed that the heterojunction exhibits an optical energy bandgap (E-g) of 1.85 eV. For laser excitation with E > Eg, the photosensitivity (S) exceeds 67 while it is less than unity for excitations with E < Eg. These behaviors are assigned to the intrinsic and extrinsic nature of absorption, respectively. In addition, S increases as a result of energy barrier height lowering with increasing light power. On the other hand, when the device was excited with ac signal, the capacitance and impedance of the device displayed a resonance-antiresonance property associated with negative differential resistance and very high signal quality factor (10(3)) above 1.37 GHz. The bandwidth of the two resonance-antiresonance peaks is 319 and 12.6 MHz at 1.475 and 1.649 GHz, respectively. These results are attractive for using the heterojunction in VLC and microwave communication technologies.Article Citation - WoS: 11Citation - Scopus: 11Optical and Electrical Performance of Yb/Inse Interface(Elsevier Sci Ltd, 2016) Alharbi, S. R.; Qasrawi, A. F.In this study a 300 nm ytterbium transparent thin film is used as substrate to a 300 nm thick InSe thin film. The optical transmittance, reflectance and absorbance of the glass/InSe and Yb/InSe films are measured and analyzed. The optical data allowed determining the effects of the Yb layer on the energy band gap, on the dielectric and on optical conductivity spectra. The band gap of the InSe films shrunk from 2.38/139 to 1.90/1.12 eV upon Yb layer interfacing leading to a band offset of 0.48/0.27 eV. On the other hand, the modeling of the optical conductivity in accordance with the Lorentz theory revealed a free carrier scattering time, carrier density and mobility of 0.225 (fs), 3.0 x 10(19)(cm(-3)) and 2.53 cm(2)/Vs for the Yb/InSe interface, respectively. As these values seem to be promising for employing the Yb/InSe interface in thin film transistor technology, the current voltage characteristics of Yb/InSe/C Schottky diode were recorded and analyzed. The electrical analysis revealed the removal of the tunneling channels by using Yb in place of Al. In addition, the "on/off' current ratios, the Schottky barrier height and the switching voltage of the Yb/InSe/C device are found to be 18.8, 0.76/0.60 eV and 0.53 V, respectively. (C) 2015 Elsevier Ltd. All rights reserved.
