Browsing by Author "Bütün, Bayram"
Now showing items 1-20 of 29
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Active metamaterial nearly perfect light absorbers: A review [Invited]
(Optical Society of America, 2019)Achieving nearly perfect light absorption from the microwave to optical region utilizing metamaterials has begun to play a significant role in photonics and optoelectronics due to their vital applications in thermal emitters, ... -
AlGaN/GaN-Based laterally gated high-electron-mobility transistors with optimized linearity
(IEEE, 2021-02-01)In this work, highly linear AlGaN/GaN laterally gated (or buried gate) high-electron-mobility transistors (HEMTs) are reported. The effect of gate dimensions on source-access resistance and the linearity of laterally gated ... -
Bismuth plasmonics for extraordinary light absorption in deep sub-wavelength geometries
(OSA - The Optical Society, 2020)In this Letter, we demonstrate an ultra-broadband metamaterial absorber of unrivaled bandwidth (BW) using extraordinary optical response of bismuth (Bi), which is the material selected through our novel analysis. Based on ... -
Bismuth-based metamaterials: From narrowband reflective color filter to extremely broadband near perfect absorber
(De Gruyter, 2019)In recent years, sub-wavelength metamaterials-based light perfect absorbers have been the subject of many studies. The most frequently utilized absorber configuration is based on nanostructured plasmonic metals. However, ... -
Colorimetric and near-absolute polarization-insensitive refractive-index sensing in all-dielectric guided-mode resonance based metasurface
(American Chemical Society, 2019)Colorimetric detection of target molecules with insensitivity to incident-light polarization has attracted considerable attention in recent years. This resulted from the ability to provide rapid output and reduced assay ... -
Effect of gate structures on the DC and RF performance of AlGaN/GaN HEMTs
(Institute of Physics Publishing, 2018)This work analyzes the effect of various gate structures on the DC and radio frequency (RF) performance of AlGaN/GaN high-electron mobility transistors (HEMTs). AlGaN/GaN HEMT devices with a 3 μm drain-to-source spacing, ... -
Fast unveiling of Tmax in GaN HEMT devices via the electrical measurement-assisted two-heat source model
(IEEE, 2022-04-07)Gallium nitride (GaN) high-electron-mobility transistor (HEMT) devices, which have wide application potential from power amplifiers to satellite, need to be thoroughly examined in terms of reliability in order to benefit ... -
Impact of the low temperature ohmic contact process on DC and forward gate bias stress operation of GaN HEMT devices
(Institute of Electrical and Electronics Engineers, 2022-08-17)In AlGaN/GaN high electron mobility transistors (HEMTs), high temperature processes (such as ohmic annealing with >800°C value) could deform the crystal structure and induce trap states within the bulk and surface. Expanded ... -
Improved Tmax estimation in GaN HEMTs using an equivalent hot point approximation
(IEEE, 2020)In this article, heat generation distribution and maximum device temperature of gallium-nitride (GaN) high-electron-mobility transistors (HEMTs) are investigated by using the 2-D electrothermal and finite-element method ... -
Investigation of a hybrid approach for normally-off GaN HEMTs using fluorine treatment and recess etch techniques
(Institute of Electrical and Electronics Engineers Inc., 2019)A hybrid approach for obtaining normally off high electron mobility transistors (HEMTs) combining fluorine treatment, recess etch techniques, and AlGaN buffer was studied. The effects of process variations (recess etch ... -
Investigation of angstrom-thick aluminium oxide passivation layers to improve the gate lag performance of GaN HEMTs
(IOP, 2019-07)In this paper, we report an angstrom-thick atomic layer deposited (ALD) aluminum oxide (Al2O3) dielectric passivation layer for an AlGaN/GaN high electron mobility transistor (HEMT). Our results show a 55% improvement in ... -
Lithography-free planar band-pass reflective color filter using a series connection of cavities
(Nature Publishing Group, 2019-01)In this article, a lithography-free multilayer based color flter is realized using a proper series connection of two cavities that shows relatively high efciency, high color purity, and a wide view angle. The proposed ... -
Lithography-free, manganese-based ultrabroadband absorption through annealing-based deformation of thin layers into metal–air composites
(OSA - The Optical Society, 2019-07-15)Fabrication, characterization, and analysis of an ultrabroadband lithography-free absorber is presented. An over 94% average absorption is experimentally achieved in the wavelength range of 450–1400 nm. This ultrabroadband ... -
Low temperature grown GaAs based resonant cavity enhanced photodiodes
(Bilkent University, 2004)High performance photodetectors operating in the 1.3 - 1.6 µm wavelength range are vital components for long-haul optical fiber communication systems. GaAs with its mature fabrication methods is one of the most used ... -
Normally-off AlGaN/GaN MIS-HEMT with low gate leakage current using a hydrofluoric acid pre-treatment
(Elsevier, 2019)We demonstrate the electrical performances of an AlGaN/GaN metal–insulator–semiconductor high electron mobility transistor (MIS-HEMT) with low gate leakage current (Ig). A low gate leakage current as low as the order of ... -
Normally-off p-GaN gate InAlN/GaN HEMTs grown on silicon substrates
(SPIE, 2019-02)A normally-off InAlN/GaN high electron mobility transistor (HEMT) on Si substrate with a p-GaN gate is reported. Devices are fabricated on two different epitaxial structures, one containing a high resistive GaN buffer layer ... -
Plasmonic enhanced terahertz time-domain spectroscopy system for identification of common explosives
(SPIE, 2017)In this study, we present a classification algorithm for terahertz time-domain spectroscopy systems (THz-TDS) that can be trained to identify most commonly used explosives (C4, HMX, RDX, PETN, TNT, composition-B and ... -
Realistic channel temperature simulation of AlGaN/GaN high electron mobility transistors
(IEEE, 2019)In this work, the realistic channel temperature of AlGaN/GaN High Electron Mobility Transistors (HEMTs) is investigated by using 2D electrothermal and Finite Element Method (FEM) thermal simulations. By using a special ... -
Spectrally selective ultrathin photodetectors using strong interference in nanocavity design
(Institute of Electrical and Electronics Engineers Inc., 2019)Thinning the active layer's thickness of the semiconductor down to a level comparable with the carriers' diffusion length while keeping its absorption high is an ultimate goal to boost the performance of optoelectronic ... -
Strong interference in planar, multilayer perfect absorbers: achieving high-operational performances in visible and near-infrared regimes
(Institute of Electrical and Electronics Engineers Inc., 2019)Light-Matter Interactions at subwavelength-designed nanostructures have been the subject of intensive study in recent years. The realization of an ideal "blackbody" absorber is an emerging topic in nanophotonics and ...
