Browsing by Subject "Quantum Efficiency"

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    ItemOpen Access
    AlxGa1-xN based solar blind Schottky photodiodes
    (2004) Tut, Turgut
    Photodetectors are essential components of optoelectronic integrated circuits and fiber optic communication systems. AlxGa1−xN is a promising material for optoelectronics and electronics. Applications include blue and green LEDs, blue laser diodes, high power-high frequency electronics, and UV photodetectors. Photodetectors that operate only in the λ < 280 nm spectrum are called solarblind detectors due to their blindness to solar radiation within the atmosphere. In this thesis, we present our efforts for the design, fabrication and characterization of Al0.38Ga62N/GaN based solar blind Schottky photodiodes. We obtained very low dark current, high quantum efficiency, high detectivity performance. Under 25 V reverse bias, we measured a maximum quantum efficiency of 71 percent at 254 nm and a maximum responsivity of 0.15 A/W at 253 nm for a 150 micron diameter device. To our knowledge, these are the best values reported in the literature. For a 30 micron device, 50 ps FWHM pulse response is observed. When the scope response is deconvoluted, a maximum 3-dB bandwidth of 4.0 GHz is obtained for 30 micron diameter Schottky photodiodes.
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    Fabrication and characterization of high-speed, high quantum efficiency, resonant cavity enhanced Schottky photodiodes
    (1998) Ata, Erhan Polatkan
    Rapidly developing “photonics” technology promises higher bcindwidths of communiccition than any other techniciue did ever. The increasing rate of communication not only alters science and technology, but brings a global cultural exchange, which seems to be one of the most important revolutions in the history. Photodetectors, as vital corniDonents of optoelectronics, cire still being developed to achieve satisfying performances for the increasing communication demcinds. We have designed and fabricated high-speed, high efficiency resonant Ccivity enhanced (RCE) Schottky photodiodes, suitable for 800-850 mil operation wavelengths. We have used two different GaAs/AlGaAs based epitaxial structures to achieve high performance. From one of these structures, we fabricated photodiodes with 50% quantum efficiency and 80 GHz 3-dB bandwidth. The other structure had a design suitable for préfabrication wavelength tuning and adjustable active layer thickness. On this structure, we achieved 20% quantum efficiency along with, world record for RGB photodiodes, over 110 (Hlz 3-dB estimated bandwidth. We investigated effects of active layer, top Au layer, and silicon nitride coating layer thicknesses on the RCE devices. Discrepancy between theory and experiments were also explained briefly. Methods for improving performances of photodiodes has been proposed ¿is possible future work. Possible appliccitions, which may make use of current knowhow on the subject, have also been mentioned.
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    ItemOpen Access
    InGaAs-based high-performance p-i-n photodiodes
    (IEEE, 2002-03) Kimukin, I.; Bıyıklı, Necmi; Butun, B.; Aytur, O.; Ünlü, S. M.; Özbay, Ekmel
    In this letter, we have designed, fabricated, and characterized high-speed and high efficiency InGaAs-based p-i-n photodetectors with a resonant cavity enhanced structure. The devices were fabricated by a microwave-compatible process. By using a postprocess recess etch, we tuned the resonance wavelength from 1605 to 1558 nm while keeping the peak efficiencies above 60%. The maximum quantum efficiency was 66% at 1572 nm which was in good agreement with our theoretical calculations. The photodiode had a linear response up to 6-mW optical power, where we obtained 5-mA photocurrent at 3-V reverse bias. The photodetector had a temporal response of 16 ps at 7-V bias. After system response deconvolution, the 3-dB bandwidth of the device was 31 GHz, which corresponds to a bandwidth-efficiency product of 20 GHz.