Abstract: In this paper, a vivid simulated study has been made on 35 GHz Ka-band window frequency in order to judge and compare the DC and high frequency properties of cubic ZnB-GaN with the existing hexagonal 4H-SiC. A flat profile p+pnn+ DDR structure of impatt is chosen and is optimized at a particular bias current density with respect to efficiency and output power taking into consideration the effect of mobile space charge also. The simulated results obtained reveals the strong potentiality of impatts based on both cubic ZnB-GaN and hexagonal 4H-SiC. The DC-to-millimeter wave conversion efficiency for cubic ZnB-GaN impatt obtained is 50% with an estimated output power of 2.83 W at an optimized bias current density of 2.5×108 A/m2. The conversion efficiency and estimated output power in case of hexagonal 4H-SiC impatt obtained is 22.34% and 40 W respectively at an optimum bias current density of 0.06×108 A/m2.
Abstract: The Al-MoO3-P-CdTe-Al MOS sandwich structures
were fabricated by vacuum deposition method on cleaned glass
substrates. Capacitance versus voltage measurements were performed
at different frequencies and sweep rates of applied voltages for oxide
and semiconductor films of different thicknesses. In the negative
voltage region of the C-V curve a high differential capacitance of the
semiconductor was observed and at high frequencies (
Abstract: This paper presents the experimental results on space charge distribution in cross-linked polyethylene (XLPE) insulating material for 22 kV power distribution system cable by using pulse electroacoustic measurement technique (PEA). Numbers of XLPE insulating material ribbon having thickness 60 μm taken from unused 22 kV high voltage cable were used as specimen in this study. DC electric field stress was applied to test specimen at room temperature (25°C). Four levels of electric field stress, 25 kV/mm, 50 kV/mm, 75 kV/mm and 100 kV/mm, were used. In order to investigate space charge distribution characteristic, space charge distribution characteristics were measured after applying electric field stress 15 min, 30 min and 60 min, respectively. The results show that applied time and magnitude of dc electric field stress play an important role to the formation of space charge.
Abstract: The purpose of this research was to analyze and compare the instability of a contact surface between Copper and Nickel an alloy cathode in vacuum, the different ratio of Copper and Copper were conducted at 1%, 2% and 4% by using the cathode spot model. The transient recovery voltage is predicted. The cathode spot region is recognized as the collisionless space charge sheath connected with singly ionized collisional plasma. It was found that the transient voltage is decreased with increasing the percentage of an amount of Nickel in cathode materials.
Abstract: In the present work, Pulsed Electro Acoustic (PEA)
technique was adopted to understand the space charge dynamics in
elastomeric material. It is observed that the polarity of the applied
DC voltage voltage and its magnitude alters the space charge
dynamics in insulation structure. It is also noticed that any addition
of compound to the base material/processing technique have
characteristic variation in the space charge injection process. It could
be concluded based on the present work that the plasticizer could
inject heterocharges into the insulation medium. Also it is realized
that space charge magnitude is less with the addition of plasticizer. In
the PEA studies, it is observed that local electric field in the
insulating material can be much more than applied electric field due
to space charge formation. One of the important conclusions arrived
at based on PEA technique is that one could understand the safe
operating electric field of an insulation material and the charge trap
sites.
Abstract: We have developed an analytic model for the radial pn-junction in a nanowire (NW) core-shell structure utilizing as a new
building block in different semiconductor devices. The potential distribution through the p-n-junction is calculated and the analytical expressions are derived to compute the depletion region widths. We
show that the widths of space charge layers, surrounding the core, are
the functions of core radius, which is the manifestation of so called classical size effect. The relationship between the depletion layer width and the built-in potential in the asymptotes of infinitely large
core radius transforms to square-root dependence specific for conventional planar p-n-junctions. The explicit equation is derived to
compute the capacitance of radial p-n-junction. The current-voltage behavior is also carefully determined taking into account the “short
base" effects.
Abstract: Degradation of polymeric insulation systems of
electrical equipments increases the space charge density and the
concentration of electrical dipoles. By consequence, the maximum
values and the slopes of absorption/resorption (A/R) currents can
change with insulation systems ageing. In this paper, an analysis of
the nature of the A/R currents and the importance of their
components, especially the polarization current and the current given
by the space charge, is presented. The experimental study concerns
the A/R currents measurements of plane samples (made from
CALMICAGLAS tapes), virgin and thermally accelerated aged. The
obtained results show that the ageing process produces an increase of
the values and a decrease of shapes of the A/R currents. Finally, the
possibility of estimating insulations ageing state and lifetime from
A/R currents measurements is discussed.
Abstract: This paper presents ageing experiments controlled by the evolution of junction parameters. The deterioration of the device is related to high injection effects which modified the transport mechanisms in the space charge region of the junction. Physical phenomena linked to the degradation of junction parameters that affect the devices reliability are reported and discussed. We have used the method based on numerical analysis of experimental current-voltage characteristic of the junction, in order to extract the electrical parameters. The simultaneous follow-up of the evolutions of the series resistance and of the transition voltage allow us to introduce a new parameter for reliability evaluation.