• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.3
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• pp.332-336
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• 2024

High-energy bandgap material silicon carbide (SiC) is gaining attention as a next-generation power semiconductor material, and in particular, SiC-based MOSFETs are developed as representative power semiconductors to increase the breakdown voltage (BV) of conventional planar structures. However, as the size of SJ (Super Junction) MOSFET devices decreases and the depth of pillars increases, it becomes challenging to uniformly form the doping concentration of pillars. Therefore, a structure with different doping concentrations segmented within the pillar is being researched. Using Silvaco TCAD simulation, a SJ VVD (vertical variation doping profile) MOSFET with three different doping concentrations in the pillar was studied. Simulations were conducted for the width of the pillar and the doping concentration of N-epi, revealing that as the width of the pillar increases, the depletion region widens, leading to an increase in on-specific resistance (R_on,sp) and breakdown voltage (BV). Additionally, as the doping concentration of N-epi increases, the number of carriers increases, and the depletion region narrows, resulting in a decrease in R_on,sp and BV. The optimized SJ VVD MOSFET exhibits a very high figure of merit (BFOM) of 13,400 KW/cm², indicating excellent performance characteristics and suggesting its potential as a next-generation highperformance power device suitable for practical applications.

• Progress in Superconductivity
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• v.4 no.1
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• pp.10-13
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• 2002

We report the effect of Ca doping in $YBa_2Cu_3O_{7-\delta}$ (YBCO) thin films grown on the Rolling- Assisted, Biaxially Textured Substrates (RABiTS) with the architecture of $CeO_2/YSZ/CeO_2/Ni$. Critical currents of bilayer and trilayer structures of $YBCO/Y_{0.7}Ca_{0.3}Ba_2Cu_3O_{7-\delta}$/(YCaBCO) as well as undoped YBCO for comparison have been measured in a wide range of temperatures and fields. For $6-8^{\circ}$ grain boundaries, 30% Ca-doping in bilayer structure enhances $J_c$ as high as 35%. The enhancement is larger at low temperatures and at magnetic fields. On the other hand, 30% Ca-doping in trilayer structure reduces $J_c$ as high as 60%. Combined with slightly lower $T_c$, this indicates that Ca is overdoped in this structure and degrades GBs.

• Journal of the Semiconductor & Display Technology
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• v.10 no.4
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• pp.61-64
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• 2011

In order to grow the crystalline solar cells industry continuously, development of alternate low-cost manufacturing processes is required. Plasma doping system is the technique for introducing dopants into semiconductor wafers in CMOS devices. In photovoltaics, plasma doping system could be an interesting alternative to thermal furnace diffusion processes. In this paper, plasma doping system was applied for phosphorus doping in crystalline solar cells. The Plasma doping was carried out in 1~4 KV bias voltages for four minutes. For removing surface damage and formation of pn junction, annealing steps were carried out in the range of $800{\sim}900^{\circ}C$ with $O_2$ ambient using thermal furnace. The junction depth in about $0.35{\sim}0.6{\mu}m$ range have been achieved and the doping profiles were very similar to emitter by thermal diffusion. So, It could be confirmed that plasma doping technique can be used for emitter formation in crystalline solar cells.

• Journal of the Korean Vacuum Society
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• v.10 no.1
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• pp.104-111
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• 2001

B-doped hydrogenated amorphous silicon carbide (a-SiC:H) thin films were prepared by plasma-enhanced chemical-vapor deposition in a gas mixture of $SiH_4, CH_4,\;and\; B_2H_6$. Physical and chemical properties of a-SiC:H films grown with varing the ratio of $B_2H_6/(SiH_4+CH_4)$ were characterized with various analysis methods including scanning electron microscopy (SEM), X-ray diffractometry (XRD), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, secondary ion mass spectroscopy (SIMS), UV absorption CH_4spectroscopy and electrical conductivity measurements. With the B-doping concentration, the doping efficiency and the micro-crystallinity were decreased and the film became amorphous when $B_2H_6/(SiH_4{plus}CH_4)$ was over $5{\times}10^{-3}$. The addition of $B_2H_6$ gas during deposition decreased the H content in the film by lowering the quantity of Si-C-H bonds. Consequently, the optical band gap and the activation energy of a-SiC:H films were decreased with increasing the B-doping level.

• Journal of Industrial and Engineering Chemistry
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• v.68
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• pp.124-128
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• 2018

Titanium doping is employed to enhance the structural strength of a high-Ni layered cathode material in lithium ion batteries during high temperature cycling. After Ti-doping, the external morphology remains similar, but the lattice parameters of the layered structure are slightly shifted toward larger values. With application of the prepared materials as cathodes in lithium-ion batteries, the initial capacities are similar but the cycling performance at $25^{\circ}C$ is enhanced by Ti-doping. During high temperature cycling at $60^{\circ}C$, furthermore, highly improved capacity retention is achieved with the Ti-doped material (95% of initial capacity at 50th cycles), while cycle fading is accelerated with the bare electrode. This enhancement is attributed to better retention of the compressive strength of the particles and retarded crack formation within the particles. In addition, impedance increase is reduced in the Ti-doped electrode, which is attributed to an improvement in the structural strength of the high-Ni cathode material with Ti-doping.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.199-200
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• 2009

This paper describes the electrical properties of polycrystalline (poly) 3C-SiC thin films with different nitrogen doping concentrations. The in-situ-doped poly 3C-SiC thin films were deposited by using atmospheric-pressure chemical vapor deposition (APCVD) at $1200^{\circ}C$ with hexamethyldisilane (HMDS: $Si_2$ $(CH_3)_6)$ as a single precursor and 0 ~ 100 sccm of $N_2$ as the dopant source gas. The peaks of the SiC (111) and the Si-C bonding were observed for the poly 3C-SiC thin films grown on $SiO_2/Si$ substrates by using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analyses, respectively. The resistivity of the poly 3C-SiC thin films decreased from $8.35\;{\Omega}{\cdot}cm$ for $N_2$ of 0 sccm to $0.014\;{\Omega}{\cdot}cm$ with $N_2$ of 100 sccm. The carrier concentration of the poly 3C-SiC films increased with doping from $3.0819\;{\times}\;10^{17}$ to $2.2994\;{\times}\;10^{19}\;cm^{-3}$, and their electronic mobilities increased from 2.433 to $29.299\;cm^2/V{\cdot}S$.

• Journal of Sensor Science and Technology
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• v.17 no.5
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• pp.325-328
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• 2008

This paper describes the electrical properties of poly (polycrystalline) 3C-SiC thin films with different nitrogen doping concentrations. In-situ doped poly 3C-SiC thin films were deposited by APCVD at $1200^{\circ}C$ using HMDS (hexamethyildisilane: $Si_2(CH_3)_6)$) as Si and C precursor, and $0{\sim}100$ sccm $N_2$ as the dopant source gas. The peak of SiC is appeared in poly 3C-SiC thin films grown on $SiO_2/Si$ substrates in XRD(X-ray diffraction) and FT-IR(Fourier transform infrared spectroscopy) analyses. The resistivity of poly 3C-SiC thin films decreased from $8.35{\Omega}{\cdot}cm$ with $N_2$ of 0 sccm to $0.014{\Omega}{\cdot}cm$ with 100 sccm. The carrier concentration of poly 3C-SiC films increased with doping from $3.0819{\times}10^{17}$ to $2.2994{\times}10^{19}cm^{-3}$ and their electronic mobilities increased from 2.433 to $29.299cm^2/V{\cdot}S$, respectively.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.156-156
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• 2016

The effect of nitrogen doping on the mechanical and tribological performance of single-layer tetrahedral amorphous carbon (ta-C:N) coatings of up to $1{\mu}m$ in thickness was investigated using a custom-made filtered cathode vacuum arc (FCVA). The results obtained revealed that the hardness of the coatings decreased from $65{\pm}4.8GPa$ to $25{\pm}2.4GPa$ with increasing nitrogen gas ratio, which indicates that nitrogen doping occurs through substitution in the $sp^2$ phase. Subsequent AES analysis showed that the N/C ratio in the ta-C:N thick-film coatings ranged from 0.03 to 0.29 and increased with the nitrogen flow rate. Variation in the G-peak positions and I(D)/I(G) ratio exhibit a similar trend. It is concluded from these results that micron-thick ta-C:N films have the potential to be used in a wide range of functional coating applications in electronics. To achieve highly conductive and wear-resistant coatings in system components, the friction and wear performances of the coating were investigated. The tribological behavior of the coating was investigated by sliding an SUJ2 ball over the coating in a ball-on-disk tribo-meter. The experimental results revealed that doping using a high nitrogen gas flow rate improved the wear resistance of the coating, while a low flow rate of 0-10 sccm increased the coefficient of friction (CoF) and wear rate through the generation of hematite (${\alpha}-Fe_2O_3$) phases by tribo-chemical reaction. However, the CoF and wear rate dramatically decreased when the nitrogen flow rate was increased to 30-40 sccm, due to the nitrogen inducing phase transformation that produced a graphite-like structure in the coating. The widths of the wear track and wear scar were also observed to decrease with increasing nitrogen flow rate. Moreover, the G-peaks of the wear scar around the SUJ2 ball on the worn surface increased with increasing nitrogen doping.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.322-322
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• 2010

For boron doping on n-type silicon wafer, around $1,000^{\circ}C$ doping temperature is required, because of the relatively low solubility of boron in a crystalline silicon comparing to the phosphorus case. Boron doping by fiber laser annealing and lamp furnace heat treatment were carried out for the uniformly deposited p-a-Si:H layer. Since the uniformly deposited p-a-Si:H layer by cluster is highly needed to be doped with high temperature heat treatment. Amorphous silicon layer absorption range for fiber laser did not match well to be directly annealed. To improve the annealing effect, we introduce additional lamp furnace heat treatment. For p-a-Si:H layer with the ratio of $SiH_4:B_2H_6:H_2$=30:30:120, at $200^{\circ}C$, 50 W power, 0.2 Torr for 30 min. $20\;mm\;{\times}\;20\;mm$ size fiber laser cut wafers were activated by Q-switched fiber laser (1,064 nm) with different sets of power levels and periods, and for the lamp furnace annealing, $980^{\circ}C$ for 30 min heat treatment were implemented. To make the sheet resistance expectable and uniform as important processes for the $p^+$ layer on a polished n-type silicon wafer of (100) plane, the Q-switched fiber laser used. In consequence of comparing the results of lifetime measurement and sheet resistance relation, the fiber laser treatment showed the trade-offs between the lifetime and the sheet resistance as $100\;{\omega}/sq.$ and $11.8\;{\mu}s$ vs. $17\;{\omega}/sq.$ and $8.2\;{\mu}s$. Diode level device was made to confirm the electrical properties of these experimental results by measuring C-V(-F), I-V(-T) characteristics. Uniform and expectable boron heavy doped layers by fiber laser and lamp furnace are not only basic and essential conditions for the n-type crystalline silicon solar cell fabrication processes, but also the controllable doping concentration and depth can be established according to the deposition conditions of layers.

• Korean Journal of Materials Research
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• v.20 no.7
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• pp.351-355
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• 2010

Transparent conducting aluminum-doped ZnO thin films were deposited using a sol-gel process. In this study, the important deposition parameters were investigated thoroughly to determine the appropriate procedures to grow large area thin films with low resistivity and high transparency at low cost for device applications. The doping concentration of aluminum was adjusted in a range from 1 to 4 mol% by controlling the precursor concentration. The annealing temperatures for the pre-heat treatment and post-heat treatment was $250^{\circ}C$ and 400-$600^{\circ}C$, respectively. The SEM images show that Al doped and undoped ZnO films were quite uniform and compact. The XRD pattern shows that the Al doped ZnO film has poorer crystallinity than the undoped films. The crystal quality of Al doped ZnO films was improved with an increase of the annealing temperature to $600^{\circ}C$. Although the structure of the aluminum doped ZnO films did not have a preferred orientation along the (002) plane, these films had high transmittance (> 87%) in the visible region. The absorption edge was observed at approximately 370 nm, and the absorption wavelength showed a blue-shift with increasing doping concentration. The ZnO films annealed at $500^{\circ}C$ showed the lowest resistivity at 1 mol% Al doping.