1,720,962 research outputs found
Electrical Stability of MOS Structures With AlON and Al2O3 Dielectrics Deposited on n-and p-Type GaN
No full textThis article discusses the electrical stability of MOS structures on n-and p-type GaN for two different dielectrics, AlON and Al2O3, deposited by atomic layer deposition (ALD). Threshold voltage hysteresis was evaluated by means of capacitance-voltage (C-V ) double sweep measurements, performed on MOS capacitors. MOS structures on p-doped GaN show up to two orders of magnitude higher effective trapped charge density than on n-GaN. Moreover, AlON results in 10 times less trapped charge than Al 2 O 3 on p-GaN. The leakage current is also identified as an important factor in defining the electrical stability at high electric fields, due to the enhanced injection of electrons into the MOS stack. Electron trapping is shown to happen either at the dielectric-semiconductor interface or in border traps. AlON results in lower flat-band and threshold voltages likely due to the resulting fixed interface charge from surface reconstruction. The effect of the n-type doping density as well as of dry etch damage on the effective trapped charge after injection has been shown to be minimal. These results are important for different insulated gate device architectures. We show that extremely low threshold voltage hysteresis values can be reached in a trench-shaped gate GaN MOSFET using AlON as an interface dielectric
Demonstration of High-quality GaN Epitaxy on 200 mm Engineered Substrates for Vertical Power Device Fabrication
No full textReliability of p-GaN gate HEMTs in reverse conduction
No full textSynchronousbuck converter comprises a low side (LS) and a high side (HS) switch, where the HS switch works in the first quadrant (forward conduction) whereas the LS switch works in the third quadrant (reverse conduction). However, the reliability of the p-GaN gate high electron mobility transistor (HEMT) in reverse conduction is unclear. In this work, a comprehensive evaluation of this conduction mode for 200-V HEMTs was conducted. First, devices were subjected to time-dependent breakdown (TDB) measurements. By comparing different device configurations, the time to failure (TTF) was found to only scalewith the number of gate fingers instead of the gate width W-G, proving the critical spots are the intersection of gate fingers over the N implantation isolation. The reverse operation voltage of V-DS for ten years lifetime was extrapolated to be -5.4 V, corresponding to a failure of 0.01% and 100 gate fingers. Second, the devices were submitted to 200-V V-DS OFF-state stress for 10 s, after which the reverse drain current saw a negligible degradation. Third, the reverse conduction of the HEMTs only showed a very limited deterioration after a long-time bias temperature instability (BTI) stress at V-DS = -5.5 V and V-GS = 0 V. This work proves the p-GaN gate HEMTs bear a high reliability in reverse conduction, which can simplify the design of synchronous power system
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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