Browsing by Subject "High quality"

Now showing 1 - 10 of 10

Open Access
Effect of the passivation layer on the noise characteristics of mid-wave-infrared InAs / GaSb superlattice photodiodes
(IEEE, 2012) Tansel, T.; Kutluer, K.; Salihoglu, Ö.; Aydınlı, Atilla; Aslan, B.; Arikan, B.; Kilinc, M. C.; Ergun, Y.; Serincan, U.; Turan, R.
The authors describe the noise characterization of a mid-wavelength- infrared (MWIR) photodiode based on indium arsenide and gallium antimonide (InAs/GaSb) superlattice (SL), addressing the influence of different passivation layers applied to the surface of the device. The MWIR InAs/GaSb SL design structure is based on p-i-n configuration grown by the molecular beam epitaxy on a (001) n-GaSb substrate. The SiO 2-passivated SL photodiodes demonstrated a Schottky-limited noise up to a bias voltage of -0.1 V where the measured peak responsivity is 1.37 A/W with a cut-off wavelength of 4.9 μm and the specific detectivity as high as 1.23 × 10 12 cm. Hz 1/2 W , demonstrating the high quality of the fabricated MWIR SL photodiodes. The noise measurements exhibited a frequency-dependent plateau (i.e., 1/f noise) for unpassivated and Si 3N 4-passivated samples, whereas 1/f-type noise suppression (i.e., frequency-independent plateau) with a noise current reduction at about 30 Hz of more than one order of magnitude was observed for the SiO 2-passivated ones.
Open Access
High quality single-crystal germanium-on-insulator on bulk Si substrates based on multistep lateral over-growth with hydrogen annealing
(American Institute of Physics, 2010-08-09) Yu, H. Y.; Cheng, S. L.; Park, J. H.; Okyay, Ali Kemal; Onbal, M. C.; Ercan, B.; Nishi, Y.; Saraswat, K. C.
Germanium-on-insulator (GOI) is desired for high performance metal-oxide-semiconductor transistors and monolithically integrated optoelectronics. We demonstrate a promising approach to achieve single-crystal defect-free GOI by using lateral over-growth through SiO2 window. The dislocations due to the lattice mismatch are effectively terminated and reduced in SiO2 trench by selective area heteroepitaxy combined with hydrogen annealing. Low defect density of 4× 106 cm-2 and low surface roughness of 0.7 nm (root-mean-square) on GOI are confirmed by plan-view transmission electron microscopy and atomic force microscopy analysis. In addition, the excellent metal-semiconductor-metal diode electrical characteristics fabricated on this GOI confirm Ge crystal quality. The selectively grown GOI structure can provide the monolithic integration of SiGe based devices on a Si very large scale integration (VLSI) platform
Open Access
High-quality InP/ZnS nanocrystals with high photometric performance and their application to white quantum dot light-emitting diodes
(IEEE, 2012) Yang, X.; Tan, S. T.; Demir, Hilmi Volkan; Sun, X. W.
Full visible range covering InP/ZnS core-shell nanocrystals with high photometric performance have been prepared. Making use of these nanocrystals, we demonstrate a white quantum dot LED with a high color rendering index of 91. © 2012 IEEE.
Open Access
Quantum dot integrated LEDs using photonic and excitonic color conversion
(Elsevier, 2011-11-23) Demir, Hilmi Volkan; Nizamoglu, S.; Erdem, T.; Mutlugun, E.; Gaponik N.; Eychmüller A.
This review summarizes advantages, recent progress and challenges related to the quickly evolving research field of colloidal quantum dot integrated LEDs based on color conversion. We start with presenting a short general introduction to the field of solid state lighting and color conversion phenomena, which are essential for defining the requirements for high-quality general lighting. Subsequently we continue with a brief description of the synthesis of nanocrystal quantum dots and their optical properties together with the advantages of utilizing them in LEDs as color convertors. Following this basic background, we review the recent efforts on quantum dot integrated color-conversion LEDs, Förster resonance energy transfer (FRET) converted LEDs and FRET-enhanced LEDs. Finally, we conclude with a future outlook on semiconductor lighting and quantum dot integrated LEDs.
Open Access
Real-time fringe pattern generation with high quality
(OSA, 2009) Kang, Hoonjong; Yaraş, Fahri; Onural, Levent; Yoshikawa, H.
A hologram computation procedure and its GPU implementation are presented. The procedure is based on partitioning. Each segment has an approximate but simpler frequency domain representation. Quality of the results is comparable to Fresnel holograms.
Open Access
Rethinking social inclusivity: Design strategies for cities
(ICE Publishing, 2011) Afacan, Yasemin; Afacan, S. O.
Cities have become more fragmented due to the increasing urbanisation of many parts of the world. There is more inequality and a growing complexity of social life in cities that leads to social exclusion and increasing social differentiation. This study approaches social inclusivity within the context of universal urban design and defines it as a vehicle for promoting human wellbeing, environmental wholeness and principles of participatory democracy. Mat urbanism - an urban form concept that is more organic and fluid than other urban forms and models - is proposed, alongside a universal design approach, to achieve the goals of sustainable communities and enhance quality of life. The relationship of mat urbanism to the features of high-quality environments and sustainable developments is questioned and illustrated with simple diagrams. The paper concludes with the importance of universally designed sets of regulatory practices regarding sustainable architecture and urban development - from individual buildings to the district and city-scale level. The contribution of this study is not only to explore the potentials of Smithson's configurations theoretically but also to open new means through which towns and cities can be planned in the future in order to promote social inclusivity, environmental responsiveness, sustainability and universal urban design.
Open Access
SAR image reconstruction by EMMP algorithm
(IEEE, 2012-04) Uǧur, Salih; Arıkan, Orhan; Gürbüz, A. C.
In this work, EMMP algorithm is used to solve the SAR image reconstruction problem which is modelled in the compressed sensing context. It is found that the sparsity parameter of the target region is an important parameter determining the quality of the output image. The proposed method is applied to the real SAR data and provided high quality outputs. © 2012 IEEE.
Open Access
Selective-area high-quality germanium growth for monolithic integrated optoelectronics
(Institute of Electrical and Electronics Engineers, 2012-03-02) Yu, H. Y.; Park, J. H.; Okyay, Ali Kemal; Saraswat, K. C.
Selective-area germanium (Ge) layer on silicon (Si) is desired to realize the advanced Ge devices integrated with Si very-large-scale-integration (VLSI) components. We demonstrate the area-dependent high-quality Ge growth on Si substrate through SiO 2 windows. The combination of area-dependent growth and multistep deposition/hydrogen annealing cycles has effectively reduced the surface roughness and the threading dislocation density. Low root-mean-square surface roughness of 0.6 nm is confirmed by atomic-force-microscope analysis. Low defect density in the area-dependent grown Ge layer is measured to be as low as 1 × 10 7cm -2 by plan-view transmission-electron-miscroscope analysis. In addition, the excellent metal-semiconductor-metal photodiode characteristics are shown on the grown Ge layer to open up a possibility to merge Ge optoelectronics with Si VLSI.
Open Access
SONIC: streaming overlapping community detection
(Springer, 2016) Sarıyüce, A. E.; Gedik, B.; Jacques-Silva, G.; Wu, Kun-Lung; Catalyurek, U.V.
A community within a graph can be broadly defined as a set of vertices that exhibit high cohesiveness (relatively high number of edges within the set) and low conductance (relatively low number of edges leaving the set). Community detection is a fundamental graph processing analytic that can be applied to several application domains, including social networks. In this context, communities are often overlapping, as a person can be involved in more than one community (e.g., friends, and family); and evolving, since the structure of the network changes. We address the problem of streaming overlapping community detection, where the goal is to maintain communities in the presence of streaming updates. This way, the communities can be updated more efficiently. To this end, we introduce SONIC—a find-and-merge type of community detection algorithm that can efficiently handle streaming updates. SONIC first detects when graph updates yield significant community changes. Upon the detection, it updates the communities via an incremental merge procedure. The SONIC algorithm incorporates two additional techniques to speed-up the incremental merge; min-hashing and inverted indexes. Results show that SONIC can provide high quality overlapping communities, while handling streaming updates several orders of magnitude faster than the alternatives performing from-scratch computation.
Open Access
Towards a quality service layer for Web 2.0
(Springer, 2011-12) Schaal, M.; Davenport, David; Çevik, Ali Hamdi
Despite the help of search engines and Web directories, identifying high quality content becomes increasingly difficult as the Internet gets ever more crowded with information. Prior approaches for filtering and searching content with respect to user-specific preferences do exist: Recommendation engines employ collaborative filtering to support subjective selection, (semi-)automatic page ranking algorithms utilize the hypertext link structure of the World Wide Web to assess page importance, and trust-based systems employ social network analysis to determine the most suitable Web pages. The use of implicit and explicit user feedback, however, is often either ignored or its exploitation is limited to isolated Web sites. We thus propose a quality overlay framework that enables the collection and processing of user-feedback, and the subsequent presentation of quality-enabled content for any Web-site. We present the quality overlay framework, propose an architecture for its realization, and validate our approach by scenarios and a detailed design with sample implementation. © 2011 Springer-Verlag.