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      •   BUIR Home
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      • Bilkent Theses
      • Theses - Department of Electrical and Electronics Engineering
      • Dept. of Electrical and Electronics Engineering - Master's degree
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      Investigation of photodetectors based on iii-nitride and metal oxide thin films deposited by atomic layer deposition

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      Embargo Lift Date: 2017-07-28
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      Author
      Tekcan, Burak
      Advisor
      Okyay, Ali Kemal
      Date
      2015-05
      Publisher
      Bilkent University
      Language
      English
      Type
      Thesis
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      Abstract
      Gallium Nitride (GaN), one of the most attractive optoelectronic materials today with a direct wide band gap of 3.4eV and high electron saturation velocity of, has found many applications from blue/UV LEDs to UV photodetectors, from high electron mobility transistors (HEMT) to solar cells. Traditional techniques to grow GaN films require high temperature (over 600C) processes. Such techniques cannot be used to synthesize GaN films on temperature sensitive substrates such as plastics or even paper for large area optoelectronic applications. To circumvent this setback, atomic layer deposition (ALD) stands out with its unique features such as low temperature process, precise thickness control and step coverage. Our work marks the demonstration of the first optical device on hollow cathode plasma assisted atomic layer deposition (HCPA-ALD) grown GaN films. The fabricated devices showed promising electrical and optical performance. A UV/VIS contrast ratio of 15 is obtained with very low dark current of 14pA at 20V applied bias. Annealing the films improved the device performance. Dark current was reduced more than two orders of magnitude while the responsivity was increased by two times. In the second part of the thesis, optoelectronic device applications on ALD grown ZnO layers will be presented. ZnO is also an attractive wide direct band gap semiconductor. It is utilized in many optical devices such as photodetectors and solar cells as well as thin film transistors and biomedical applications. In this work, device applications of ZnO on Silicon heterojunctions are investigated. A high rectification ratio of 103 is achieved with 80C grown ZnO-Si heterojunction photodiodes. High responsivity values are also recorded for these devices. At 350nm incident wavelength maximum responsivity of 35mA/W and at 585nm incident wavelength maximum responsivity of 90mA/W are obtained.
      Keywords
      Gallium nitride (GaN)
      Zinc oxide (ZnO)
      Atomic layer deposition
      Metal-semiconductor-metal
      P-n heterojunction photodiode
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      http://hdl.handle.net/11693/29014
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      • Dept. of Electrical and Electronics Engineering - Master's degree 594
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