Browsing by Subject "Ohmic contacts"

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    1.3 μm GaAs based resonant cavity enhanced Schottky barrier internal photoemission photodetector
    (IEEE, Piscataway, NJ, United States, 2000) Necmi, B.; Kimukin, I.; Özbay, Ekmel; Tuttle, G.
    GaAs based photodetectors operating at 1.3 μm that depend on internal photoemission as the absorption mechanism were fabricated. Quantum efficiency (QE) was increased using resonant cavity enhancement (RCE) effect.
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    45 GHz bandwidth-efficiency resonant cavity enhanced ITO-Schottky photodiodes
    (OSA, 2001) Bıyıklı, Necmi; Kimukin, İbrahim; Aytür, Orhan; Özbay, Ekmel; Gökkavas, M.; Ünlü, M. S.
    We demonstrated high-performance resonant cavity enhanced ITO-Schottky photodiodes. We achieved a peak efficiency of 75% around 820 nm with a 3-dB bandwidth of 60 GHz resulting in a bandwidth-efficiency product of 45 GHz.
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    High-performance 1.55 μm resonant cavity enhanced photodetector
    (IEEE, 2002) Kimukin, İbrahim; Bıyıklı, Necmi; Özbay, Ekmel
    A high speed and high efficiency resonant cavity enhanced InGaAs based photodetector was demonstrated. A peak quantum efficiency of 66% was measured along with 31 GHz bandwidth with the device. The photoresponse was found to be linear upto 6 mW optical power, where the device 5 mA photocurrent.
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    High-performance solar-blind AlGaN photodetectors
    (IEEE, 2004) Özbay, Ekmel; Bıyıklı, Necmi; Kimukin, İbrahim; Tut, Turgut; Kartaloğlu, Tolga; Aytür, Orhan
    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 deposition (MOCVD) on sapphire structures. n+ and p+ ohmic contacts on GaN were formed with non-annealed titanium (Ti)/aluminum (Al) and nickel (Ni)/ gold (Au) alloys. Spectral UV photoresponse measurements confirmed the solar-blind response of the devices.
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    High-speed resonant-cavity-enhanced Schottky photodiodes
    (IEEE, 1998) Ata, Erhan P.; Bıyıklı, Necmi; Demirel, Ekrem; Özbay, Ekmel; Gökkavas, M.; Onat, B.; Ünlü, M. S.; Tuttle, G.
    The top-illuminated Schottky photodiodes were fabricated by a microwave-compatible monolithic microfabrication process. Fabrication started with formation of ohmic contacts to n+ layers. Mesa isolation was followed by a Ti-Au interconnect metallization. Following this, a semitransparent Au Schottky metal and a silicon nitride layer was deposited. Finally, a thick Ti-Au layer was deposited to form an air bridge connection between the interconnect and the Schottky metal. The optical properties of the photodiodes were simulated using a transfer matrix method.
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    High-speed widely-tunable >90% quantum-efficiency resonant cavity enhanced p-i-n photodiodes
    (IEEE, 1998) Bıyıklı, Necmi; Kimukin, İbrahim; Aytür, Orhan; Gökkavas, M.; Ulu, G.; Mirin, R.; Christensen, D. H.; Ünlü, M. S.; Özbay, Ekmel
    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 Bragg mirrors made of quarter-wave Al0.20Ga0.80As/AlAs stacks. Photoresponse and photospectral measurements were carried out. The tuning of the resonance wavelength within the Bragg mirror's upper and lower edges was observed. Quantum efficiency greater than 90% was demonstrated.
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    In-situ focused ion beam implantation for the fabrication of a hot electron transistor oscillator structure
    (1996) Kaya I.I.; Dellow, M.W.; Bending, S.J.; Linfield, E.H.; Rose P.D.; Ritchie, D.A.; Jones G.A.C.
    Recent advances using in situ focused ion beam implantation during an MBE growth interruption have been exploited to fabricate planar GaAs hot electron structures without the need for shallow ohmic contacts. This novel fabrication route shows a very high yield and has been used to demonstrate a prototype high-frequency oscillator structure based on electron multiplication in the base layer. Existing devices show transfer factors in excess of unity as well as reversal of the base current at high injection levels, which are the prerequisites for oscillator action. Future improvements in device design are discussed.
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    Solar-blind A1GaN-based p-i-n photodiodes with low dark current and high detectivity
    (IEEE, 2004) Bıyıklı, Necmi; Kimukin, I.; Aytur, O.; Özbay, Ekmel
    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 up to 6 V. The device responsivity increased with reverse bias and reached 0.11 A/W at 261 nm under 10-V reverse bias. The detectors exhibited a cutoff around 283 nm, and a visible rejection of four orders of magnitude at zero bias. Low dark current values led to a high differential resistance of 9.52 × 1015 Ω. The thermally limited detectivity of the devices was calculated as 4.9 × 1014 cm · Hz1/2W-1. © 2004 IEEE.