1,022 research outputs found
Faust i smert' : Tragedija na 3 diï, 9 scen / O. Levada
No full textFAUST I SMERT' : TRAGEDIJA NA 3 DIÏ, 9 SCEN / O. LEVADA
Faust i smert' : Tragedija na 3 diï, 9 scen / O. Levada (1)
Cover (3)
Titelseite (4)
Ill. (Portr.) (5)
Personen (6)
Faust i smert'. Tragedija na 3 dii, 9 scen (7
Нlukhiv’s appearances of V. Narbut´s poem «Levada»
No full textУ статті подається авторський варіант розшифрування
образів вірша В. Нарбута «Левада».В статье рассматривается авторская версия расшифровки
образов в стихотворении В. Нарбута «Левада».The author version of decoding of appearances in the V.Narbut´s
poem»Levada» is examined in the article
Нlukhiv’s appearances of V. Narbut´s poem «Levada»
No full textУ статті подається авторський варіант розшифрування
образів вірша В. Нарбута «Левада».В статье рассматривается авторская версия расшифровки
образов в стихотворении В. Нарбута «Левада».The author version of decoding of appearances in the V.Narbut´s
poem»Levada» is examined in the article
Donation and organ transplantation in public opinion of Russians
No full textThis article is a part of a public report of the survey carried out by the Levada-Center, dedicated to the study of the problems of organ donation in Russia. On the basis of a nationwide survey of public opinion the author analyzes views and positions of Russians in relation to organ donation
Reliability of visible GaN LEDs in plastic package
No full textThis work presents the results of extensive high-current accelerated aging tests carried out on blue and white
InGaN/GaN LEDs packaged with the usual epoxy encapsulation (lamps) in order to investigate both package degradation and
chip-related failure modes. As a result, the following package related failure modes were identified: (i) in blue lamps, high current
levels and high junction temperatures, induce degradation of the epoxy material in contact with the heated device surface, leading
to the formation of an opaque layer on the device surface; (ii) in white lamps tested at high current levels converting phosphors
degradation has been observed, suggesting degradation of their white light converting efficiency; (iii) contact resistance increasing
induced by die attach degradation has been observed in both white and blue lamps, finally (iv) plastic carbonization has been
observed along the wire bonding suggesting power- or temperature-related cover plastic degradation that can contribute to the
observed optical power degradatio
The role of Mg complexes in the degradation of InGaN-based LEDs
No full textThe electrical and optical properties of commercial blue InGaN-based LEDs after room
temperature aging tests at DC-forward currents from 50 to 100 mA are studied by Current–Voltage,
Capacitance–Voltage, Electroluminescence and Cathodoluminescence techniques. An increase of the
reverse and low-bias forward currents, of the parasitic series resistance and a substantial optical
intensity reduction are observed in all the devices investigated with or without heat sink. In addition,
only in devices aged at 100 mA without heat sink, the onset of a broad optical band peaked at about
3.1 eV and an apparent doping decrease of about four times, as obtained by Capacitance–Voltage
measurements, are found. Temperature-dependent luminescence analyses show the quenching of the
3.1 eV band above 200 K, suggesting its donor–acceptor-pair nature. The band onset is interpreted as
a result of the Mg dopant instability in the p-type layers, correlated to the device self-heating inducing
junction temperature above 300 ◦C. The band is attributed toMg-related metastable complexes, such
as Mg–H2, acting as shallow acceptors. Due to their unstable nature, the behaviour of the 3.1 eV
emission is studied under controlled electron-beam irradiation in the SEM. Its time evolution during
60 min of irradiation reveals an almost complete quenching in the Cathodoluminescence spectra,
which is attributed to the dissociation of the Mg–H2 complexes
Reliability analysis of Gan-Based LEDs for solid state illumination
No full textHigh-brightness, high-efficiency GaN-based LEDs have already found many applications, and are extremely
promising devices for solid-state lighting, including general illumination [1]. While reliability of LEDs is significantly
better in most aspects compared to traditional light sources, lumen maintenance remains one of the critical issues
concerning this new technology. Early reliability studies [2] observed a rapid loss of light output, severe degradation of
the transparent encapsulating material under blue and UV illumination and elevated temperatures; non-optimized
packaging also induced other reliability problems due to difficulties in thermal management. As the packaging
technology improves, the interest is focussing on failure modes and mechanisms related with the semiconductor
material and the die technology, which have been less investigated in the past.
This work presents the results of extensive high-current accelerated aging tests carried out on blue InGaN/GaN
LEDs packaged with the usual epoxy encapsulation (lamps) as well as mounted without encapsulation (chips), in order
to isolate the chip-related failure modes. As a result, 5 distinct failure modes were identified: (i) in encapsulated
devices, testing at high current levels and, consequently, at high junction temperatures, induces degradation of the
epoxy material in contact with the heated device surface, leading to the formation of an opaque layer on the device
surface; (ii) high current and temperature affect the semi-transparent ohmic contact on top of the device, leading to
increase in series resistance, with consequent current crowding effects that reduce the optical power; (iii) an increase
in doping of the p-type layer takes place, possibly due to decomposition of Mg complexes [3,4], and Mg reactivation;
(iv) Deep Level Transient Spectroscopy (DLTS) detects changes in the distribution of deep levels already present in
untreated devices, and also a generation of shallow traps; (v) both DLTS and photocurrent spectra indicate the
creation of extended defects in devices treated at high current density. Identification of the specific failure mechanisms
allows an accurate extrapolation of LED lifetime, and suggests specific actions for improving device reliability
Accelerated aging of GaN light emitting diodes studied by 1/f and RTS noise
No full textBecause of their ultra brightness, GaN light emitting diodes (LEDs) becomes a promising light sources for
daily lighting. The growing market requires high reliability and long lifetime. Degradation mechanisms due to
accelerated ageing in GaN LED have previously been investigated by capacitance spectroscopy or light emission
mapping. In this paper low frequency noise (LFN) is used as a diagnostic tool to study degradation
mechanisms in GaN LEDs submitted to accelerated agein
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