Now showing items 1-20 of 21

    • 45-GHz bandwidth-efficiency resonant-cavity-enhanced ITO-Schottky photodiodes 

      Bıyıklı, Necmi; Kimukin, I.; Aytür, O.; Gökkavas, M.; Ünlü, M. S.; Özbay, Ekmel (IEEE, 2001)
      High-speed Schottky photodiodes suffer from low efficiency mainly due to the thin absorption layers and the semitransparent Schottky-contact metals. We have designed, fabricated and characterized high-speed and high-efficiency ...
    • Characterization of AlInN/AlN/GaN heterostructures with different AlN buffer thickness 

      Çörekçi, S.; Dugan, S.; Öztürk, M. K.; Çetin, S. Ş.; Çakmak, M.; Özçelik, S.; Özbay, Ekmel (Springer New York LLC, 2016)
      Two AlInN/AlN/GaN heterostructures with 280-nm- and 400-nm-thick AlN buffer grown on sapphire substrates by metal-organic chemical vapor deposition (MOCVD) have been investigated by x-ray diffraction (XRD), atomic force ...
    • Direct magnetic imaging of ferromagnetic domain structures by room temperature scanning hall probe microscopy using a bismuth micro-Hall probe 

      Sandhu, A.; Masuda, H.; Oral, A.; Bending, S. J. (Japan Society of Applied Physics, 2001)
      A bismuth micro-Hall probe sensor with an integrated scanning tunnelling microscope tip was incorporated into a room temperature scanning Hall probe microscope system and successfully used for the direct magnetic imaging ...
    • Dual-color ultraviolet metal-semiconductor-metal AlGaN photodetectors 

      Gökkavas, M.; Bütün, S.; Yu, H.; Tut, T.; Bütün, B.; Özbay, Ekmel (AIP Publishing LLC, 2006)
      Backilluminated ultraviolet metal-semiconductor-metal photodetectors with different spectral responsivity bands were demonstrated on a single Alx Ga1-x N heterostructure. This was accomplished by the incorporation of an ...
    • The effect of growth conditions on the optical and structural properties of InGaN/GaN MQW LED structures grown by MOCVD 

      Cetđn, S.; Sağlam, S.; Ozcelđk, S.; Özbay, Ekmel (Gazi University Eti Mahallesi, 2014)
      Five period InGaN/GaN MQW LED wafers were grown by low pressure MOCVD on an AlN buffer layer, which was deposited on a c-plane (0001)-faced sapphire substrate. The effect of growth conditions, such as the well growth time, ...
    • Fabrication of high-speed resonant cavity enhanced schottky photodiodes 

      Özbay, Ekmel; Islam, M. S.; Onat, B.; Gökkavas, M.; Aytür, O.; Tuttle, G.; Towe, E.; Henderson, R. H.; Ünlü, M. S. (Institute of Electrical and Electronics Engineers, 1997-05)
      We report the fabrication and testing of a GaAs-based high-speed resonant cavity enhanced (RCE) Schottky photodiode. The top-illuminated RCE detector is constructed by integrating a Schottky contact, a thin absorption ...
    • High-performance ALGaN-based visible-blind resonant cavity enhanced Schottky photodiodes 

      Kimukin, İbrahim; Bıyıklı, Necmi; Kartaloğlu, Tolga; Aytür, Orhan; Özbay, Ekmel (Materials Research Society, 2003-04)
      We have designed, fabricated and tested resonant cavity enhanced visible-blind AlGaN-based Schottky photodiodes. The bottom mirror of the resonant cavity was formed with a 20 pair AlN/AlGaN Bragg mirror. The devices were ...
    • High-performance solar-blind AlGaN photodetectors 

      Özbay, Ekmel; Bıyıklı, Necmi; Kimukin, İbrahim; Tut, Turgut; Kartaloğlu, Tolga; Aytür, Orhan (IEEE, 2004)
      High-performance aluminum gallium nitride (AlGaN)-based solar-blind (SB) photodetectors were demonstrated using different device structures. The Al x-Ga1-xN layers structure were grown by metalorganic chemical vapor ...
    • High-performance solar-blind photodetectors based on AlxGa 1_xN heterostructures 

      Özbay, Ekmel; Bıyıklı, Necmi; Kimukin, I.; Kartaloglu, T.; Tut, T.; Aytür, O. (IEEE, 2004)
      Design, fabrication, and characterization of high-performance AI xGa1-xN-based photodetectors for solar-blind applications are reported. AlxGa1-xN heterostructures were designed for Schottky. p-i-n, and metal-semicondnctor-metal ...
    • High-speed 1.55 μm operation of low-temperature-grown GaAs-based resonant-cavity-enhanced p-i-n photodiodes 

      Butun, B.; Bıyıklı, Necmi; Kimukin, I.; Aytur, O.; Özbay, Ekmel; Postigo, P. A.; Silveira, J. P.; Alija, A. R. (American Institute of Physics, 2004)
      The 1.55 μm high-speed operation of GaAs-based p-i-n photodiodes was demonstrated and their design, growth and fabrication were discussed. A resonant-cavity-detector structure was used to selectively enhance the photoresponse ...
    • High-speed GaAs-based resonant-cavity-enhanced 1.3-μm photodetector 

      Özbay, Ekmel; Kimukin, İbrahim; Bıyıklı, Necmi; Gary, T. (SPIE, 2000)
      High-speed photodetectors operating at 1.3 and 1.55 μm are important for long distance fiber optic based telecommunication applications. We fabricated GaAs based photodetectors operating at 1.3 μm that depend on internal ...
    • High-speed solar-blind photodetectors with indium-tin-oxide Schottky contacts 

      Bıyıklı, Necmi; Kimukin, I.; Kartaloglu, T.; Aytur, O.; Özbay, Ekmel (American Institute of Physics, 2003)
      AlGaN/GaN-based high-speed solar-blind photodetectors were discussed. Current-voltage, spectral responsivity, and high-frequency response characterizations were performed. Breakdown voltages larger than 40 V were obtained. ...
    • High-speed widely-tunable >90% quantum-efficiency resonant cavity enhanced p-i-n photodiodes 

      Bıyıklı, Necmi; Kimukin, İbrahim; Aytür, Orhan; Gökkavas, M.; Ulu, G.; Mirin, R.; Christensen, D. H.; Ünlü, M. S.; Özbay, Ekmel (IEEE, 1998)
      Widely-tunable high-speed resonant cavity enhanced p-i-n photodiodes were designed, fabricated and tested for operation around 820 nm. The structure was grown by solid-source MBE on GaAs substrates and features high-reflectivity ...
    • Highly directive radiation and negative refraction using photonic crystals 

      Özbay, Ekmel; Bulu, I.; Aydin, K.; Caglayan H.; Alici, K. B.; Guven, K. (Institute of Physics Publishing, 2005)
      In this article, we present an experimental and numerical study of certain optical properties of two-dimensional dielectric photonic crystals (PCs). By modifying the band structure of a two-dimensional photonic crystal ...
    • Hot electron effects in unipolar n-type submicron structures based on GaN, AlN and their ternary alloys 

      Sevik, C.; Bulutay, C. (The Institution of Engineering and Technology, 2003)
      The authors present an analysis of impact ionisation (II) and related hot electron effects in submicron sized GaN, AlN and their ternary alloys, all of which can support very high field regimes, reaching a few megavolts ...
    • Hydrodynamic approach for modelling transport in quantum well device structures 

      Besikci, C.; Tanatar, Bilal; Sen, O. (Institute of Physics Publishing Ltd., 1998)
      A semiclassical approach for modelling electron transport in quantum well structures is presented. The model is based on the balance equations governing the conservation of particle density, momentum and energy with Monte ...
    • Mg-doped AlGaN grown on an AlN/sapphire template by metalorganic chemical vapour deposition 

      Yu, H.; Strupinski, W.; Butun, S.; Özbay, Ekmel (2006)
      The growth of high-performance Mg-doped p-type Al xGa 1-xN (x = 0.35) layers using low-pressure metal-organic chemical vapour deposition on an AlN/sapphire template is reported. The influence of growth conditions on the ...
    • Raman scattering from confined phonons in GaAs/AlGaAs quantum wires 

      Bairamov, B. H.; Aydınlı, Atilla; Tanatar, Bilal; Güven, K.; Gurevich, S.; Mel'tser, B. Ya.; Ivanov, S. V.; Kop'ev, P. S.; Smirnitskii, V. B.; Timofeev, F. N. (Academic Press, 1998)
      We report on photoluminescence and Raman scattering performed at low temperature (T = 10 K) on GaAs/Al 0.3Ga 0.7As quantum-well wires with effective wire widths of L = 100.0 and 10.9 nm prepared by molecular beam epitaxial ...
    • Solar-blind A1GaN-based p-i-n photodiodes with low dark current and high detectivity 

      Bıyıklı, Necmi; Kimukin, I.; Aytur, O.; Özbay, Ekmel (IEEE, 2004)
      We report solar-blind AlxGal1-xN-based heterojunction p-i-n photodiodes with low dark current and high detectivity. After the p+ GaN cap layer was recess etched, measured dark current was below 3 fA for reverse bias values ...
    • Study of wet oxidized AlxGa1-xAs for integrated optics 

      Bek, A.; Aydınlı, Atilla; Champlain, J. G.; Naone, R.; Dagli, N. (Institute of Electrical and Electronics Engineers, 1999)
      An investigation of wet oxidized AlxGa1-xAs layers in integrated optical applications is reported. Refractive index and thickness shrinkage of wet oxidized AlxGa1-xAs layers are measured using spectroscopic ellipsometry. ...