• Transactions on Electrical and Electronic Materials
• /
• v.12 no.4
• /
• pp.148-151
• /
• 2011

We designed and fabricated aluminium gallium nitride (AlGaN)/GaN high electron mobility transistors (HEMTs) with stable reverse blocking characteristics established by employing a selective fluoride plasma treatment on the drainside gate edge region where the electric field is concentrated. Implanted fluoride ions caused a depolarization in the AlGaN layer and introduced an extra depletion region. The overall contour of the depletion region was expanded along the drift region. The expanded depletion region distributed the field more uniformly and reduced the field intensity peak. Through this field modulation, the leakage current was reduced to 9.3 nA and the breakdown voltage ($V_{BR}$) improved from 900 V to 1,400 V.

• Transactions on Electrical and Electronic Materials
• /
• v.14 no.4
• /
• pp.177-181
• /
• 2013

In this paper, silicon solar cells are analyzed regarding power conversion efficiency by changed capacitance in the depletion region. For the capacitance control in the depletion region of silicon solar cell was applied for 10, 20, 40, 80, 160 and 320 Hz frequency band character and alternating current(AC) voltage with square wave of 0.2~1.4 V. Academically, symmetry formation of positive and negative change of the p-n junction is similar to the physical effect of capacitance. According to the experiment result, because input of square wave with alternating current(AC) voltage could be observed to changed capacitance effect by indirectly method through non-linear power conversion (Voltage-Current) output. In addition, when input alternating current(AC) voltage in the silicon solar cell, changed capacitance of depletion region with the forward bias condition and reverse bias condition gave a direct effect to the charge mobility.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.39 no.1
• /
• pp.1-11
• /
• 2002

In this paper, new simple method for the calculation of depletion region under complex geometry and general purpose numerical simulator that could handle this were developed and applied in the analysis of SCM with nanoscale tip, which is a promising tool for high resolution dopant profiling. Our simple depletion region seeking algorithm alternatively switches material of elements to align ionized element boundary with contour of zero potential. To prove the validity of our method we examined whether our results satisfy the definition of depletion region and compared those with known values of un junction and MOS structure. By modeling of capacitance based on the shape of depletion region and potential distribution, we could calculate the CV curve and dC/dV curve between silicon substrate and nanoscale SCM tip.

• Proceedings of the KIEE Conference
• /
• 1998.07d
• /
• pp.1337-1339
• /
• 1998

The trench termination scheme is introduced for high voltage devices. The curvature of the depletion region at field limiting ring is critical factor to determine the breakdown voltage. The smooth curvature of the depletion junction alleviate the electric field crowding effect around this region. In the trench field limiting ring, the radius of the depletion region is smaller than conventional field limiting ring, but the distance between every trench is spaced small enough to punchthrough before initiation of local breakdown. The trench field limiting ring on silicon can ne formed by RIE followed by oxidation on side wall surface of the trench, and polysilicon filling. The combined termination of this trench floating field ring and field plate have been designed and analyzed. The breakdown simulation by 2-dimensional TCAD shows that the cylindrical junction breakdown voltage for substrate doping might be 99 percent of the ideal breakdwon voltage for substrate doping concentration of $3\times10^{14}cm^{-3}$ with about $100{\mu}m$ of lateral termination width.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.10 no.2
• /
• pp.152-159
• /
• 2010

We propose a semi-analytical current conduction model for depletion-mode n-type nanowire field-effect transistors (NWFETs) with top-gate structure. The NWFET model is based on an equivalent circuit consisting of two back-to-back Schottky diodes for the metal-semiconductor (MS) contacts and the intrinsic top-gate NWFET. The intrinsic top-gate NWFET model is derived from the current conduction mechanisms due to bulk charges through the center neutral region as well as of accumulation charges through the surface accumulation region, based on the electrostatic method, and thus it includes all current conduction mechanisms of the NWFET operating at various top-gate bias conditions. Our previously developed Schottky diode model is used for the MS contacts. The newly developed model is integrated into ADS, in which the intrinsic part of the NWFET is developed by utilizing the Symbolically Defined Device (SDD) for an equation-based nonlinear model. The results simulated from the newly developed NWFET model reproduce considerably well the reported experimental results.

• Journal of the Korean Ceramic Society
• /
• v.32 no.4
• /
• pp.419-428
• /
• 1995

Polycrystalline silicon carbide (SiC) thick films were depostied by low pressure chemical vapor deposition (LPCVD) using CH3SiCl3 (MTS) and H2 gaseous mixture onto isotropic graphite substrate. Effects of deposition variables on the SiC film were investigated. Deposition rate had been found to be surface-reaction controlled below reactor temperature of 120$0^{\circ}C$ and mass-transport controlled over 125$0^{\circ}C$. Apparent activation energy value decreased below 120$0^{\circ}C$ and deposition rate decreased above 125$0^{\circ}C$ by depletion effect of the reactant gas in the direction of flow in a horizontal hot wall reactor. Microstructure of the as-deposited SiC films was strongly influenced by deposition temperature and position. Microstructural change occurred greater in the mass transport controlled region than surface reaction controlled region. The as-deposited SiC layers in this experiment showed stoichiometric composition and there were no polytype except for $\beta$-SiC. The preferred orientation plane of the polycrystalline SiC layers was (220) plane at a high reactant gas concentration in the mass transfer controlled region. As depletion effect of reactant concentration was increased, SiC films preferentially grow as (111) plane.

• Transactions on Electrical and Electronic Materials
• /
• v.17 no.2
• /
• pp.104-108
• /
• 2016

To research the correlation between oxygen vacancy and the electrical characteristics of ZTO, which is made by using a target mixed ZnO:SnO₂=1:1, the ZnO, SnO₂ and ZTO were analyzed by PL, XPS, XRD patterns and electrical properties. It was compared with the electron orbital spectra of O 1s in accordance with the electrical characteristics of ZnO, SnO₂ and ZTO. The electrical characteristics of ZTO were improved by increasing the annealing temperatures, due to the high degree of crystal structures at a high temperature, and the physical properties of ZTO was similar to that of ZnO. The amorphous structure of SnO₂ was increased with increasing the temperature. The Schottky contact of oxide semiconductors was formed using the depletion region, which is increased by the electron-hole combination due to the annealing processes. ZnO showed the Ohmic contact in spite of a high annealing temperature, but SnO₂ and ZTO had Schottky contact. As such, it was confirmed that the electrical properties of ZTO are affected by the molecules of SnO₂.

• Journal of Korean Society of Forest Science
• /
• v.95 no.5
• /
• pp.532-538
• /
• 2006

Triphala is an important combination of three important forest fruits, i.e., Emblica officinalis, Terminalia chebula and Terminalia bellirica. Chittagong region in Bangladesh was once rich in triphala trees presently subject to the depletion. Thus, these forest resources are being threatened day by day. The study was conducted to learn the present using pattern of the triphala, causes of its depletion and the conservation strategies agreed by the villagers. Eight major uses of triphala trees were recognized. It was revealed that 100% respondents used the triphala as fruit tree followed by 71-78% as fuelwod. The present status of growing stock of triphala was found in depleted condition particularly in the Muslim dominated area. It was found that unawareness was the major cause for depleting the triphala trees agreed by the 87% respondents followed by depleting the village groves by 84%. Awareness creation (100%) and induction of social forestry program (92%) were found major recomendations by the vilagers to retard depleting the triphala tree species in the Chittagong region of Bangladesh.

• Nuclear Engineering and Technology
• /
• v.55 no.7
• /
• pp.2516-2533
• /
• 2023

Several practical methods for accelerating the depletion calculation in a GPU-based Monte Carlo (MC) code PRAGMA are presented including the multilevel spectral collapse method and the vectorized Chebyshev rational approximation method (CRAM). Since the generation of microscopic reaction rates for each nuclide needed for the construction of the depletion matrix of the Bateman equation requires either enormous memory access or tremendous physical memory, both of which are quite burdensome on GPUs, a new method called multilevel spectral collapse is proposed which combines two types of spectra to generate microscopic reaction rates: an ultrafine spectrum for an entire fuel pin and coarser spectra for each depletion region. Errors in reaction rates introduced by this method are mitigated by a hybrid usage of direct online reaction rate tallies for several important fissile nuclides. The linear system to appear in the solution process adopting the CRAM is solved by the Gauss-Seidel method which can be easily vectorized on GPUs. With the accelerated depletion methods, only about 10% of MC calculation time is consumed for depletion, so an accurate full core cycle depletion calculation for a commercial power reactor (BEAVRS) can be done in 16 h with 24 consumer-grade GPUs.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.1
• /
• pp.45.2-45.2
• /
• 2018

CS molecule is known to be adsorbed onto dust in cold dense cores, causing its significant depletion in the center region of cores. This study is aimed to investigate the depletion of CS molecule with optically thin $C^{34}S$ molecular line observations, including significance of its differentiation depending on the evolutionary status of the dense cores. We mapped five evolved starless cores, L1544, L1552, L1689B, L694-2 and L1197 using two molecular lines, $C^{34}S$ (J=2-1) and $N_2H^+$ (J=1-0) with NRO 45 m telescope. The $H^2$ column density and temperature structures of each targets were obtained by SED fitting for Herschel continuum images and the internal number density profiles by model fitting. All of the integrated intensity maps of $C^{34}S$ show depletion holes and 'semi-ring-like' distribution, indicating that the depletion of CS is clear and general. The radial profiles of CS abundance also show significant decrease towards the core center, while $N_2H^+$ abundance is almost constant or enhanced. We find that the more evolved cores with higher $H^2$ density tend to have a stronger depletion of CS. Our data strongly support claims that CS molecule generally depletes out in the central regions of starless dense cores and such chemical differentiation is closely related to their evolution.