Browsing by Subject "Fabrication process"

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    High-speed solar-blind AlGaN-based metal-semiconductor-metal photodetectors
    (Wiley, 2003) Bıyıklı, Necmi; Kimukin, İbrahim; Kartaloğlu, Tolga; Aytür, Orhan; Özbay, Ekmel
    Solar-blind AlGaN metal-semiconductor-metal (MSM) photodetectors with fast pulse response have been demonstrated. The devices were fabricated on MOCVD-grown epitaxial Al0.38Ga0.62N layers, using a microwave compatible fabrication process. The photodiode samples exhibited low leakage with dark current densities below 1 × 10-6 A/cm 2 at 40 V reverse bias. Photoconductive gain-assisted photoresponse was observed with a peak responsivity of 1.26 A/W at 264 nm. A visible rejection of ∼3 orders of magnitude at 350 nm was demonstrated. Temporal high-speed measurements at 267 nm resulted in fast pulse responses with 3-dB bandwidths as high as 5.4 GHz. This corresponds to a record high-speed performance for solar-blind detectors. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA.
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    Low-voltage small-size double-arm MEMS actuator
    (2009) Bıyıklı, Necmi; Damgaci, Y.; Cetiner, B.A.
    The fabrication and characterisation of a double-arm cantilever-type metallic DC-contact MEMS actuator with low pull-down voltage are reported. Bi-layer TiW cantilevers with an internal stress gradient were fabricated using a microwave-compatible fabrication process. Owing to its small size, cantilever length (L=5-50m) and width (W=2-40m), i.e. ∼10-100 times smaller in lateral dimensions than a standard MEMS actuator, this actuator showed actuation voltages lower than 10 V. RF measurements of the 10m-wide actuators yielded an average insertion loss less than 1dB and isolation higher than 40dB up to 25GHz. The developed actuator is well suited for integration in reconfigurable microwave circuits and systems such as reconfigurable antennas and arrays. © 2009 The Institution of Engineering and Technology.
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    Novel microstrip fed mechanically tunable combline cavity filter
    (IEEE, 2013) Kurudere, S.; Erturk, V. B.
    A novel configuration for mechanically tunable combline bandpass filters is proposed, where the classical resonating rod-tuning screw combination is replaced with a simple printed circuit-tuning screw combination. Moreover, because a printed circuit structure that uses metal vias forms the bottom part of the cavity, the coaxial type feeding and the coaxial to cavity matching of classical combline filters are also replaced with a microstrip feeding. Consequently, the proposed configuration provides smaller size, less weight, integration with other printed circuits and significant simplification in the fabrication process. A prototype filter is designed and fabricated for verification. The measured results are in good agreement with the simulation, and the filter exhibits very good harmonic suppression.
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    Solar-blind AlGaN-based Schottky photodiodes with low noise and high detectivity
    (American Institute of Physics, 2002) Bıyıklı, Necmi; Aytur, O.; Kimukin, I.; Tut, T.; Özbay, Ekmel
    We report on the design, fabrication, and characterization of solar-blind Schottky photodiodes with low noise and high detectivity. The devices were fabricated on n-/n+ AlGaN/GaN heterostructures using a microwave compatible fabrication process. True solar-blind operation with a cutoff wavelength of ∼274nm was achieved with AlxGa1-xN (x=0.38) absorption layer. The solar-blind detectors exhibited <1.8nA/cm2 dark current density in the 0-25 V reverse bias regime, and a maximum quantum efficiency of 42% around 267 nm. The photovoltaic detectivity of the devices were in excess of 2.6×1012cmHz1/2/W, and the detector noise was 1/f limited with a noise power density less than 3×10-29A2/Hz at 10 kHz. © 2002 American Institute of Physics.
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    Triangular metallic gratings for large absorption enhancement in thin film Si solar cells
    (Optical Society of American (OSA), 2012) Battal, E.; Yogurt, T.A.; Aygun L.E.; Okyay, Ali Kemal
    We estimate high optical absorption in silicon thin film photovoltaic devices using triangular corrugations on the back metallic contact. We computationally show 21.9% overall absorptivity in a 100-nmthick silicon layer, exceeding any reported absorptivity using single layer gratings placed on the top or the bottom, considering both transverse electric and transverse magnetic polarizations and a wide spectral range (280 - 1100 nm). We also show that the overall absorptivity of the proposed scheme is relatively insensitive to light polarization and the angle of incidence. We also discuss the implications of potential fabrication process variations on such a device. © 2012 Optical Society of America.