Browsing by Author "Khanfar, H. K."

Now showing 1 - 6 of 6

Citation - WoS: 3
Citation - Scopus: 3
Current Transport Mechanism in Au-p-mgo-ni Schottky Device Designed for Microwave Sensing
(Natl inst Optoelectronics, 2016) Qasrawi, A. F.; Khanfar, H. K.; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering
Au/MgO/Ni back to back Schottky tunnelling barriers are designed on the surface of an MgO thin layer and are electrically characterized. The current voltage curve analysis has shown that thermionic emission, field effect thermionic (FET) emission and space charge limited current are dominant transport mechanism in distinct biasing regions. It was shown that, while the device is reverse biased with voltages less than 0.31 V, it conducts by tunnelling (FED though an energy barrier of 0.88 eV with a depletion region width of 15.7 nm. As the voltage exceeds 0.46 V, the tunnelling energy barrier is lowered to 0.76 eV and the depletion region widens and arrives at the reach-through running mode. The device was tested in the microwave electromagnetic power range that extends from Bluetooth to WLAN radiation levels at oscillating frequencies of 0.5 and 2.9 GHz. In addition, a low power resonating signal that suits mobile data is superimposed in the device. It was observed that the Au/MgO/Au sensors exhibit a wide tunability range via voltage biasing or via frequency control. The signal quality factor is 3.53 x 10(3) at 2.9 GHz. These properties reflect applicability in microwave technology as wireless and connectorized microwave amplifiers, microwave resonators and mixers.
Citation - WoS: 2
Citation - Scopus: 2
Effects of Laser Excitation and Temperature on Ag/Gase_{0.5< Microwave Filters}
(Springer, 2014) Qasrawi, A. F.; Khanfar, H. K.; Department of Electrical & Electronics Engineering
The effects of temperature, illumination, and microwave signals on Ag/GaS0.5S0.5/C Schottky-type microwave filters have been investigated. The devices, which were produced from thin layers of GaSe0.5S0.5 single crystal, had room temperature barrier height and ideality factor of 0.65 eV and 3.28, respectively. Barrier height increased uniformly with increasing temperature, at 2.12 x 10(-2) eV/K, and the ideality factor approached ideality. The devices can even function at 95A degrees C. A current switching phenomenon from low to high injection ("On/Off") was also observed; this current switching appears at a particular voltage, V (s), that shifts toward lower values as the temperature is increased. When the devices were reverse-biased and illuminated with a laser beam of wavelength 406 nm, a readily distinguishable V (s) was observed that shifted with increasing laser power. When the devices were run in passive mode and excited with an ac signal of power 0.0-20.0 dBm and frequency 0.05-3.0 GHz they behaved as band filters that reject signals at 1.69 GHz. Device resistance was more sensitive to signal amplitude at low frequencies (50 MHz) than at high frequencies. The features of these Ag/GaS0.5S0.5/C Schottky devices imply that they may be used as optical switches, as self standing, low band-pass, band reject filters, and as high band-pass microwave filters.
Citation - WoS: 3
Citation - Scopus: 3
Investigations of 2.9-Ghz Resonant Microwave-Sensitive Ag/Mgo Tunneling Diodes
(Springer, 2013) Qasrawi, A. F.; Khanfar, H. K.; Department of Electrical & Electronics Engineering
In this work, a resonant microwave-sensitive tunneling diode has been designed and investigated. The device, which is composed of a magnesium oxide (MgO) layer on an amorphous germanium (Ge) thin film, was characterized by means of temperature-dependent current (I)-voltage (V), room-temperature differential resistance (R)-voltage, and capacitance (C)-voltage characteristics. The device resonating signal was also tested and evaluated at 2.9 GHz. The I-V curves reflected weak temperature dependence and a wide tunneling region with peak-to-valley current ratio of similar to 1.1. The negative differential resistance region shifts toward lower biasing voltages as temperature increases. The true operational limit of the device was determined as 350 K. A novel response of the measured R-V and C-V to the incident alternating-current (ac) signal was observed at 300 K. Particularly, the response to a 100-MHz signal power ranging from the standard Bluetooth limit to the maximum output power of third-generation mobile phones reflects a wide range of tunability with discrete switching property at particular power limits. In addition, when the tunnel device was implanted as an amplifier for a 2.90-GHz resonating signal of the power of wireless local-area network (LAN) levels, signal gain of 80% with signal quality factor of 4.6 x 10(4) was registered. These remarkable properties make devices based on MgO-Ge interfaces suitable as electronic circuit elements for microwave applications, bias- and time-dependent electronic switches, and central processing unit (CPU) clocks.
Citation - WoS: 11
Citation - Scopus: 12
Performance of the Au/Mgo Photovoltaic Devices
(Elsevier Sci Ltd, 2015) Khanfar, H. K.; Qasrawi, A. F.; Department of Electrical & Electronics Engineering
A 100 mu m thick MgO film is used to design a metal semiconductor metal device. The device is characterized by means of current voltage characteristics in the dark and under various light energies in the photon energy range of 3.70-2.15 eV. A photovoltaic effect presented by an open circuit voltage of 0.12-0.47 V. short circuit current density of 3.9-10.5 mu A/cm(2), quantum efficiency of 0.662-0.052, and responsivity of 0.179-0.024 A/W under photoexcitation optical power of 2.2-28.2 mu W is observed. The device was also tested as a UV optical communication component. The test revealed a wide range of tunability and sensitivity for microwave resonant frequencies of 0.5 and 2.9 GHz. The differential resistance of the device exhibited different values at each applied ac signal frequency. When the frequency is fixed, the illuminated to the dark current ratio remained constant for all signal powers in the range of 0.00-20.0 dBm. (C) 2014 Elsevier Ltd. All rights reserved.
Citation - WoS: 2
Role of Au Nanosheets in Enhancing the Performance of Yb/Zns Tunneling Photosensors
(Natl inst R&d Materials Physics, 2020) Abusaa, M.; Qasrawi, A. F.; Assad, B. M.; Khanfar, H. K.; Department of Electrical & Electronics Engineering
In this study, the effects of Au nanosheets of thicknesses of 50 nm on the structural, electrical and photoelectrical properties of Yb/ZnS/CdS/Au (ZAC-0) devices is considered. Stacked layers of ZnS and CdS which are prepared by the thermal evaporation technique onto Yb substrates under vacuum pressure of 10(-5) mbar exhibits rectifying characteristics. For these diodes a reverse to forward current ratios of similar to 10(5) at biasing voltage of 0.60 V is determined. Insertion of Au nanosheets between the stacked layers of ZnS and CdS increased the current values by three orders of magnitude and changed the current conduction mechanism from thermionic emission to tunneling under reverse biasing conditions. The ZAC-0 device, exhibit a barrier height lowering and barrier widening upon insertion of Au nanosheets. After the participation of Au nanosheets in the structure of the ZAC-0 devices, large photosensitivity and responsivity accompanied with high external quantum efficiency is observed. The responsivity to 406 nm laser radiation is biasing voltage dependent and reaches 135 mA/W at 0.60 V. The features of the Yb/ZnS/Au/CdS/Au photosensors nominate them as promising candidates for use in light communication technology as signal receivers.
Citation - WoS: 1
Citation - Scopus: 1
Structural, Optical and Dielectric Performance of Molybdenum Trioxide Thin Films Sandwiched With Indium Sheets
(inst Materials Physics, 2020) Abusaa, M.; Qasrawi, A. F.; Kmail, H. K.; Khanfar, H. K.; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics Engineering
In this work, we report the enhancements in the structural, optical and dielectric properties of molybdenum trioxide that are achieved by insertion of 50 and 100 nm thick indium sheets between layers of MoO3. The films which are coated onto ultrasonically glass substrates under a vacuum pressure of 10 -5 mbar exhibited metal induced crystallization process upon insertion of indium sheets. Optically, indium sheets tuned the transmittance and reflectance, significantly, increased the absorption coefficient values and formed interbands in the band gap of MoO3. The energy band gap decreased with increasing indium sheets thickness. On the other hand, the insertion of indium layers into the structure of MoO3 is observed to improve the dielectric response of these films to values that nominate them for used in thin film transistor technology. In the same context, the analyses of the optical conductivity which are carried out with the help of Drude-Lorentz approach have shown that the presence of indium sheets can increase the optical conductivity and enhance the plasmon frequency and free charge carrier density of MoO3. The plasmon frequency is tuned in the range of 1.68-7.16 GHz making MoO3 films attractive for plasmonic applications.