تصنيع وتوصيف متحسس اشعة فوق البنفسجية باستخدام اغشية اوكسيد الخارصين الرقيقة == Fabrication And Characterization Of ZnO Thin Film Based Uv Photodetectors
Author name:
الاء كريم حسن
Supervisor name:
رعد حمدان ظاهر | غصون محسن علي
General topic:
Electrical, Electronic and Communications Engineering
Specific topic:
Electrical and Electronic Engineering
Degree:
Master
University:
Mustansiriyah University - College Of Engineering - Department Of Electrical Engineering
Language:
English
University location:
Baghdad
First pages:
34T517 - p.pdf
Abstract:
في السنوات الاخيرة، كان هناك اهتمام متزايد في اشباه موصلات اوكسيد الخارصين للتطبيقات الضوئية ضمن منطقة الاطوال الموجية الفوق البنفسجية وذلك لكون طاقة اثارة الربط كبيرة (60 meV) وطاقة الفجوة الواسعة (3.37 eV) في درجة حرارة الغرفة. في هذا العمل, ثلاث متحسس | In recent years, there has been increasing interest in Zinc Oxide (ZnO) semiconductors for optoelectronic applications in the Ultraviolet (UV) region due to its large exciton binding energy (60 meV) and wide bandgap energy (3.37 eV). In this work, three devices of Metal Semiconductor Metal (MSM) UV photodetectors (PDs) and photoconductors (PCDs) based on ZnO were fabricated in the form of Interdigitated (IDT) MSM structures. The ZnO thin films were prepared by sol - gel spin coating technique, and deposited on a P - type Si and glass substrates. The Nickel (Ni) and Aluminum (Al) contacts were deposited by a vacuum coating deposition technique. The morphological, structural and electrical properties of the ZnO thin films were estimated by using Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), X - Ray diffraction (XRD), four - point probe and Hall effect measurements. Optical bandgap of ZnO film was evaluated using a double beam spectrophotometer. With applied voltage in the range ( - 5 to 5 V), the photocurrent, contrast ratio, gain, responsivity, detectivity, and Noise Equivalent Power (NEP) were estimated. The Photodetectors were illuminated with UV of 254 nm at room temperature (27 °C) and under different levels of optical power ranging between (163.2 ?w ? 172.3?w). Current Voltage (I - V) characteristics were studied and the values of the saturation current (I - s), ideality factor (n), barrier height (? - B), reach - through voltage (VRT) and flat - band voltage (VFB) were extracted under dark condition. Data analysis and curves were plotted using origin software (graphing and data analysis). The AFM and SEM images clearly demonstrate the formation of well - aligned ZnO, with smooth nanometer granular structure, dense and a good morphology. The grain size and average roughness (rms) values were found to be (59 nm, 12 nm) on Si substrate and (31 nm, 2 nm) on glass substrate, respectively.For Ni/ZnO/Ni MSM PD on Si substrate, the device has VRT of (0.56 V) and VFB of (1.5 V). The responsivity and detectivity were estimated to be (1.334 A/W and 3×1011cmHz 1/2 W - 1), respectively. I - s was found to be (8.3×10 - 7 A), n (4.4) and ? - B (0.67 eV). However for Al/ZnO/Al MSM PCDs on Si and on glass substrates, the responsivity and detectivity were (0.45 A/W and 1.2×1011 cmHz 1/2W1) and (0.94 A/W and 2.9×1011 cmHz 1/2 W - 1), respectively.The I - V measurement results obtained indicate that, the Ni/ZnO/Ni MSM PD on Si substrate behaves as a typical Schottky contact and the dominant current transport mechanism is field thermionic emission. However semi linear behavior for Al/ZnO/Al PCD on Si substrate and the current flowing through the junction was following thermionic emission mechanism, while a symmetric I - V behaviors and an excellent linear relationship between the current and applied voltage are observed in both direction for Al/ZnO/Al MSM PCD on glass substrate. The estimated responsivities, detectivities with fairly low dark currents make the diodes attractive for practical UV detector applications
