Impact of Gate Offset in Gate Recess on DC and RF Performance of InAlAs/InGaAs InP-based HEMTs

In this work, a set of 100-nm gate-length InP-based HEMTs were designed and fabricated with different gate offsets in gate recess. A novel technology was proposed for independent definition of gate recess and T-shaped gate by electron beam lithography. DC and RF measurement was conducted. With the gate offset varying from drain side to source side, the maximum drain current (Ids,max) and transconductance (gm,max) increased. In the meantime, f T decreased while f max increased, and the highest f max of 1096 GHz was obtained. It can be explained by the increase of gate-source capacitance and the decrease of gate-drain capacitance and source resistance. Output conductance was also suppressed by gate offset toward source side. This provides simple and flexible device parameter selection for HEMTs of different usage.

Factors affecting the development of Phytophthora infestans on a tomato in the open ground

Relevance and methods. For the Non-chernozem zone, the main factor for the active development of late blight is the low air temperature and its sharp fluctuations during the day, contributing to the formation of increased air humidity and drip-liquid moisture on the plants. In the Moscow region, the causative agent of late blight is manifested almost annually. Populations of Phytophthora infestans are represented by the To and T1 races. Epiphytotic development was observed periodically (1977-1979, 1982, 1986, 1996-1999, 2000, 2001, 2003-2004, 2008-2009, 2013, 2014, 2015, 2016, 2017, 2019) and was provided by the virulent T1 race. Observations showed that epiphytotic situations arose in those years when the minimum air temperature was below long-term average values, and relative humidity and precipitation exceeded them. With a deviation from the norm in the direction of increasing temperature, decreasing rainfall and relatively low humidity, years were observed with a depressive (1992, 1994) or moderate development of the disease (1980, 1981, 1983, 1985, 1987-1991, 2002, 2005-2007, 2010-2012, 2018). Results. As a result of breeding work, a Grot tomato-tolerant tomato variety was obtained, on the basis of which varieties with high resistance Grand, Dubok, Gnom, Chelnok, Patris, Geya, Zolushka, Perst, Severyanka, Blagodatny were obtained. In the general collection of VIR as a source resistance to leaf spot pathogens were registered: Geya (v.k. 14839), Slavyanka (v.k. 14840), Patrice (v.k. 14841), Rossiyanka (v.k. 14842), Krepysh (v.k. 14843), Sibiryachka (v.k. 14444) and line 1079-94 (v.k. 14845) donors, in addition to their high resistance to late blight, have excellent economic characteristics.

Soybean collection of the Institute of Agriculture of the Steppe of the NAАS and its breeding value in the conditions of the Steppe of Ukraine.

The collection soybean nursery at the Institute of Steppe Agriculture of the National Academy of Agrarian Sciences of Ukraine includes 144 varieties of domestic and foreign selection. The variety of the studied samples allows to allocate to a greater extent economically; valuable signs and to pick up parental forms for selection of soybeans on various directions of use. The results of research in the collection nursery for 10 years (2010–2019) are given. In the course of research the collection varieties of soybeans of different ecological and geographical origin were used. Collectible varieties by yield, protein and fat content in seeds were analyzed. The importance of varieties resistant to cotyledonousbacteriosis in increasing soybean yield has been substantiated. Soybean varieties of different ecological and geographical origin have been evaluated for resistance to cotyledon bacteriosis. Phytopathological assessment was performed on a natural infectious background. 15 soybean varieties resistant to cotyledonousbacteriosis were identified: Era 2, Medeya, Stepovychka 4, Diona, Agat, Sribna Ruta, Podolsk 2000, Yatran, Khabarovska 01, Evans, Liniia № 100, R8606I-5R05, Yutro, and VNIIOZ 11. Highlighted highly resistant varieties are promising as a source resistance to cotyledonousbacteriosis during selection for immunity to this pathogen. Highly resistant soybean varieties of Ukrainian selection deserve the most attention as donors of resistance to cotyledonousbacteriosis, 9 of which have been identified. At the present stage of selection, with the transition to European standards, it is very important to create varieties with high quality seeds. Therefore, the laboratory is conducting research to identify high-protein and high-fat varieties. Analyzing the results of chemical analysis of soybean varieties of different maturity groups, we can say that the protein content in the seeds varied between 32.2–45.8 %. The highest indicator was observed in the varieties Zernoukisna (45.8 %), Ustya (45.5 %), Sonyachna (44.7 %), Artemida (44.2 %), Pripyat (44.0 %). The fat content in the seeds of varieties of the collection nursery ranged from 18.2 to 26.8 %. The highest rate of fat content in seeds was observed in varieties – Emerald (26.8 %), Annushka (26.4 %), Sophia (26.8 %), Colorful (26.4 %), Ophelia (26.5 %), Podilska 416 (26.4 %), Vasylkivska (26.8 %), L. 101 (26.8 %), Bukuriya (26.3 %). Examples of high-yielding, high-protein and fat-containing, highly resistant to cotyledonousbacteriosis, as well as varieties adapted to adverse environmental conditions are given. Keywords: soy, bean, variety, collection, yield, protein, fat, resistance, seeds.

Investigation of AlGaN/GaN HFET and VO2 Thin Film Based Deflection Transducers Embedded in GaN Microcantilevers

The static and dynamic deflection transducing performances of piezotransistive AlGaN/GaN heterojunction field effect transistors (HFET) and piezoresistive VO2 thin films, fabricated on GaN microcantilevers of similar dimensions, were investigated. Deflection sensitivities were tuned with the gate bias and operating temperature for embedded AlGaN/GaN HFET and VO2 thin film transducers, respectively. The GaN microcantilevers were excited with a piezoactuator in their linear and nonlinear oscillation regions of the fundamental oscillatory mode. In the linear regime, the maximum deflection sensitivity of piezotransistive AlGaN/GaN HFET reached up to a 0.5% change in applied drain voltage, while the responsivity of the piezoresistive VO2 thin film based deflection transducer reached a maximum value of 0.36% change in applied drain current. The effects of the gate bias and the operation temperature on nonlinear behaviors of the microcantilevers were also experimentally examined. Static deflection sensitivity measurements demonstrated a large change of 16% in drain-source resistance of the AlGaN/GaN HFET, and a similarly high 11% change in drain-source resistance in the VO2 thin film, corresponding to a 10 μm downward step bending of the cantilever free end.

Investigations on the Resistance Reduction Effect of Double-Trench SiC MOSFETs under Repetitive Avalanche Stress

The unexpected resistance reduction effect of double-trench SiC MOSFETs under repetitive avalanche stress is investigated in this work. After enduring repetitive avalanche stress, the ON-state drain-source resistance (Rdson) of the device decreases. With the help of TCAD simulations, the dominant mechanism is proved to be the injection of positive charges into the gate trench bottom oxide, which is almost irreversible under zero-voltage bias condition at room temperature. For the injected positive charges attract extra electrons just beneath the gate trench bottom, where the carriers pass through under ON state, the resistivity there is reduced, improving the conduction capability of the device. Moreover, an optimization method is proposed. Since the impact ionization rate (I.I.) and the vertical oxide electric field (E⊥) along the gate trench bottom oxide interface contribute to the injection of positive charges, it is recommended to make the bottom oxide thicker to suppress this effect.