• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.6
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• pp.655-661
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• 2013

In this paper, the 1/f noise characteristics of n-channel MOSFET (NMOSFET) and p-channel MOSFET (PMOSFET) are analyzed in depth as a function of body bias. The normalized drain current noise, $S_{ID}/I_D{^2}$ showed strong dependence on the body bias in the sub-threshold region for both NMOSFET and PMOSFET, and NMOSFET showed stronger dependence than PMOSFET on the body bias. On the contrary, both of NMOSFET and PMOSFET do not exhibit the dependence of $S_{ID}/I_D{^2}$ on body bias in strong inversion region, although the noise mechanisms of two MOSFETs are different from each other.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.4
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• pp.303-317
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• 2013

Two novel clocking strategies for a high-speed multi-channel serializer-deserializer (SERDES) are proposed in this paper. Both of the clocking strategies are based on groups, which facilitate flexibility and expansibility of the SERDES. One clocking strategy is applicable to moderate parallel I/O cases, such as high density, short distance, consistent media, high temperature variation, which is used for the serializer array. Each group within the strategy consists of a full-rate phase-locked loop (PLL), a full-rate delay-locked loop (DLL), and two fixed phase alignment (FPA) techniques. The other is applicable to more awful I/O cases such as higher speed, longer distance, inconsistent media, serious crosstalk, which is used for the deserializer array. Each group within the strategy is composed of a PLL and two DLLs. Moreover, a half-rate version is chosen to realize the desired function of 1:2 deserializer. Based on the proposed clocking strategies, two representative ICs for each group of SERDES are designed and fabricated in a standard $0.18{\mu}m$ CMOS technology. Measurement results indicate that the two SERDES ICs can work properly accompanied with their corresponding clocking strategies.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.4
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• pp.291-302
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• 2013

NAND flash memory (NFM) based storage devices, e.g. Solid State Drive (SSD), are rapidly replacing conventional storage devices, e.g. Hard Disk Drive (HDD). As NAND flash memory technology advances, its specification has evolved to support denser cells and larger pages and blocks. However, efforts to fully understand their impacts on design objectives such as performance, power, and cost for various applications are often neglected. Our research shows this recent trend can adversely affect the design objectives depending on the characteristics of applications. Past works mostly focused on improving the specific design objectives of NFM based systems via various architectural solutions when the specification of NFM is given. Several other works attempted to model and characterize NFM but did not access the system-level impacts of individual parameters. To the best of our knowledge, this paper is the first work that considers the specification of NFM as the design parameters of NAND flash storage devices (NFSDs) and analyzes the characteristics of various synthesized and real traces and their interaction with design parameters. Our research shows that optimizing design parameters depends heavily on the characteristics of applications. The main contribution of this research is to understand the effects of low-level specifications of NFM, e.g. cell type, page size, and block size, on system-level metrics such as performance, cost, and power consumption in various applications with different characteristics, e.g. request length, update ratios, read-and-modify ratios. Experimental results show that the optimized page and block size can achieve up to 15 times better performance than the conventional NFM configuration in various applications. The results can be used to optimize the system-level objectives of a system with specific applications, e.g. embedded systems with NFM chips, or predict the future direction of NFM.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.6
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• pp.581-588
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• 2013

This paper presents a study of the process temperature dependence of $Al_2O_3$ film grown by thermal atomic layer deposition (ALD) as a passivation layer in the crystalline Si (c-Si) solar cells. The deposition rate of $Al_2O_3$ film maintained almost the same until $250^{\circ}C$, but decreased from $300^{\circ}C$. $Al_2O_3$ film deposited at $250^{\circ}C$ was found to have the highest negative fixed oxide charge density ($Q_f$) due to its O-rich condition and low hydroxyl group (-OH) density. After post-metallization annealing (PMA), $Al_2O_3$ film deposited at $250^{\circ}C$ had the lowest slow and fast interface trap density. Actually, $Al_2O_3$ film deposited at $250^{\circ}C$ showed the best passivation effects, that is, the highest excess carrier lifetime (${\tau}_{PCD}$) and lowest surface recombination velocity ($S_{eff}$) than other conditions. Therefore, $Al_2O_3$ film deposited at $250^{\circ}C$ exhibited excellent chemical and field-effect passivation properties for p-type c-Si solar cells.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.5
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• pp.492-499
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• 2013

We have investigated the electrical properties of Ru/Ni/n-GaN Schottky structure using current-voltage (I-V) and capacitance-voltage (C-V) measurements at room temperature. The barrier height (${\Phi}_{bo}$) and ideality factor (n) of Ru/Ni/n-GaN Schottky structure are found to be 0.66 eV and 1.44, respectively. The ${\Phi}_{bo}$ and the series resistance ($R_S$) obtained from Cheung's method are compared with modified Norde's method, and it is seen that there is a good agreement with each other. The energy distribution of interface state density ($N_{SS}$) is determined from the I-V measurements by taking into account the bias dependence of the effective barrier height. Further, the interface state density $N_{SS}$ as determined by Terman's method is found to be $2.14{\times}10^{12}\;cm^{-2}\;eV^{-1}$ for the Ru/Ni/n-GaN diode. Results show that the interface state density and series resistance has a significant effect on the electrical characteristics of studied diode.

• Journal of Forest and Environmental Science
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• v.7 no.1
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• pp.23-34
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• 1990

Based on the topographical and vegetational indicators on sediment movement of Yongcheon River, the movement occurence years were estimated. 1. The cross sectional shapes of deposits in torrential stream are stepped and even-aged forests tend to be established on each step. 2. Generally the older the forest age is, the higher the height of step from the lowest base tend to become. 3. The ages of trees indicate the year when deposition occured, and so may be useful as plant indicator to get chronological information.

• Journal of Forest and Environmental Science
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• v.30 no.1
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• pp.91-100
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• 2014

This research was conducted on the conservation area of Baekdudaegan, Kangwondo under the purpose of evaluating bio-diversity according to the changes of spatial scale, using GIS data and spatial filtering method. The diversity index was calculated based on the information of species of The $5^{th}$ forest type map using Shannon-weaver index (H'), evenness index ($E_i$) and richness index ($R_i$). The diversity index was analyzed and compared according to the changes of 12 spatial scales from Kernel size $3{\times}3$ to $73{\times}73$ and basin unit. As for H' and $R_i$, spatial scale increased as diversity index decreased, while $E_i$ decreases gradually. H' and $R_i$ was highest; each 1.1 and 0.6, when the Kernel size was $73{\times}73$, while $E_i$ was 0.2, the lowest. When you look at according to the basin unit, for large basin unit, 'YeongDong' region shows higher diversity index than 'YeongSeo' region. For middle basin unit, 'Gangneung Namdaecheon' region, and for small basin unit, 'Gangneung Namdaecheon' and 'Gangneung Ohbongdaem' region shows high diversity index. When you look at the relationship between diversity index and Geographic factors, H' shows positive relation to curvature and sunshine factor while shows negative to elevation, slope, hillshade, and wetness index. Also $E_i$ was similar to the relationship between H' and Geographic factor. Meanwhile, $R_i$ shows positive relationship to curvature and sunshine factor, while negative to elevation, slope, hillshade, and wetness index. macro unit diversity index evaluation was possible through the GIS data and spatial filtering, and it can be a good source for local biosphere conservation policy making.

• Journal of Forest and Environmental Science
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• v.34 no.3
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• pp.199-208
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• 2018

Quercus floribunda (Tilonj oak) is among the five species of Quercus and an evergreen tree found in Kumaun Himalayan region. Timing of germination is a crucial event determining the success of seedling establishment and survival. The aims of the study were to investigate the effect of sowing date on the germination and morphological responses of Tilonj oak (Quercus floribunda), cultivated during the month of August-September, with supplementary irrigation. The experiment was conducted by sowing seeds at two dates with one month interval in glass house conditions at DSB Campus, Nainital, Uttarakhand, India. Present study revealed that higher germination percentage (46.67 %) was recorded at sowing time $S_2$ as compared to the sowing time $S_1$ (32.86 %). Germination percentage as well as seedling growth were affected by sowing date though the differences were insignificant. At both the sowing dates, highest germination percentage was recorded for large seeds (32.86-46.67 %) followed by medium (31.43-33.33 %) and lowest germination (6.67-7.14 %) was recorded for small size seeds. In all parameters assessed, sowing time $S_2$ had the best performance in combination with large seed size. Thus, September is suitable month for best germination, growth and seedling vigour and large seed size is recommended to silviculturists and tree planters. The information on seed germination and seedling growth is vital both for conservation and rehabilitation of degraded lands.

• Journal of IKEEE
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• v.19 no.3
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• pp.342-348
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• 2015

High speed implementation of digital filters is required in high data rate applications such as hard-wired wide band modem and high resolution video codec. Since the critical path of the digital filter is the MAC (multiplication and accumulation) circuit, the filter coefficient with sparse non-zero bits enables high speed implementation with adders of low hardware cost. Compressive sensing has been reported to be very successful in sparse representation and sparse signal recovery. In this paper a filter design method for digital FIR filters with CSD (canonic signed digit) coefficients using compressive sensing technique is proposed. The sparse non-zero signed bits are selected in the greedy fashion while pruning the mistakenly selected digits. A few design examples show that the proposed method can be utilized for designing sparse CSD coefficient digital FIR filters approximating the desired frequency response.

• Journal of IKEEE
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• v.19 no.3
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• pp.295-303
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• 2015

Considering to Energy Storage System (ESS) is a global trend In order to reduce global warming and carbon emissions. South Korea has announced various policies to vitalize the development and uptake of renewable energy. South Korea is planning the cumulative capacity of ESS of two million kW in 2020. According to the government support and development of technology companies, the battery of ESS prices are expected to fall gradually. In this paper, we develop a planning model that take into account the supply expansion of technology of ESS and prices. Based on planning model, we analyze the cost of ESS linked with wind power and the revenue for trading electricity and renewable energy certifications.