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Article 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: 9Transient and Steady State Photoelectronic Analysis in Tlinse2 Crystals(Pergamon-elsevier Science Ltd, 2011) Qasrawi, A. F.; Gasanly, N. M.The temperature and illumination effects on the transient and steady state photoconductivities of TlInSe2 crystals have been studied. Namely, two recombination centres located at 234 and at 94 meV and one trap center located at 173 meV were determined from the temperature-dependent steady state and transient photoconductivities, respectively. The illumination dependence of photoconductivity indicated the domination of sublinear and supralinear recombination mechanisms above and below 160 K, respectively. The change in the recombination mechanism is attributed to the exchange of roles between the linear recombination at the surface and trapping centres in the crystal, which become dominant as temperature decreases. The transient photoconductivity measurement allowed the determination of the capture coefficient of traps for holes as 3.11 x 10(-22) cm(-2). (C) 2011 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.
