• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.2
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• pp.223-229
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• 2017

This paper analyzes the effect of a dual-metal-gate structure on the electrical characteristics of AlGaN/GaN metal-insulator-semiconductor high electron mobility transistors. These structures have two gate metals of different work function values (${\Phi}$), with the metal of higher ${\Phi}$ in the source-side gate, and the metal of lower ${\Phi}$ in the drain-side gate. As a result of the different ${\Phi}$ values of the gate metals in this structure, both the electric field and electron velocity in the channel become better distributed. For this reason, the transconductance, current collapse phenomenon, breakdown voltage, and radio frequency characteristics are improved. In this work, the devices were designed and analyzed using a 2D technology computer-aided design simulation tool.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.131-131
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• 2009

Silicon Carbide (SiC) is a material with a wide bandgap (3.26eV), a high critical electric field (~2.3MV/cm), a and a high bulk electron mobility ($\sim900cm^2/Vs$). These electronic properties allow high breakdown voltage, high-speed switching capability, and high temperature operation compared to Si devices. Although various SiC DMOSFET structures have been reported so far for optimizing performances, the effect of channel dimension on the switching performance of SiC DMOSFETs has not been extensively examined. This paper studies different channel dimensons ($L_{CH}$ : $0.5{\mu}m$, $1\;{\mu}m$, $1.5\;{\mu}m$) and their effect on the the device transient characteristics. The key design parameters for SiC DMOSFETs have been optimized and a physics-based two-dimensional (2-D) mixed device and circuit simulator by Silvaco Inc. has been used to understand the relationship. with the switching characteristics. To investigate transient characteristic of the device, mixed-mode simulation has been performed, where the solution of the basic transport equations for the 2-D device structures is directly embedded into the solution procedure for the circuit equations. We observe an increase in the turn-on and turn-off time with increasing the channel length. The switching time in 4H-SiC DMOSFETs have been found to be seriously affected by the various intrinsic parasitic components, such as gate-source capacitance and channel resistance. The intrinsic parasitic components relate to the delay time required for the carrier transit from source to drain. Therefore, improvement of switching speed in 4H-SiC DMOSFETs is essential to reduce the gate-source capacitance and channel resistance.

• Journal of the Korean Vacuum Society
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• v.14 no.1
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• pp.29-34
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• 2005

The degradation of the SiGe hetero-junction bipolar transistor(HBT) properties in SiGe BiCMOS process was investigated in this paper. The SiGe HBT prepaired by SiGe BiCMOS process, unlike the conventional one, showed the degraded DC characteristics such as the decreased Early voltage, the decreased collector-emitter breakdown voltage, and the highly increased base leakage current. Also, the cutoff frequency(f/sub T/) and the maximum oscillation frequency(f/sub max/) representing the AC characteristics are reduced to below 50%. These deteriorations are originated from the change of the locations of emitter-base and collector-base junctions, which is induced by the variation of the doping profile of boron in the SiGe base due to the high-temperature source-drain annealing. In the result, the junctions pushed out of SiGe region caused the parastic barrier formation and the current gain decrease on the SiGe HBT device.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.5
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• pp.430-433
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• 2017

This paper presents a S/C/X-band LNA MMIC with resistive feedback structure in 0.25 um GaN HEMT process. The GaN devices have advantages as a high output power device having high breakdown voltage, energy band gap and stability at high temperature. Since the receiver using the GaN device with high linearity can be implemented without a limiter, the noise figure of the receiver can be improved and the size of receiver module can be reduced. The proposed GaN LNA MMIC based on 0.25 um GaN HEMT device is achieved the gain of > 15 dB, the noise figure of < 3 dB, the input return loss of > 13 dB, and the output return loss of > 8 dB in the S/C/X-band. The current consumption of GaN LNA MMIC is 70 mA with the drain voltage 20 V and the gate voltage -3 V.

• The KIPS Transactions:PartC
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• v.9C no.6
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• pp.831-840
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• 2002

Due to the advance of computer and communication technology, intrusions or crimes using a computer have been increased rapidly while tremendous information has been provided to users conveniently Specially, for the security of a database which stores important information such as the private information of a customer or the secret information of a company, several basic suity methods of a database management system itself or conventional misuse detection methods have been used. However, a problem caused by abusing the authority of an internal user such as the drain of secret information is more serious than the breakdown of a system by an external intruder. Therefore, in order to maintain the sorority of a database effectively, an anomaly defection technique is necessary. This paper proposes a method that generates the normal behavior profile of a user from the database log of the user based on an association mining method. For this purpose, the Information of a database log is structured by a semantically organized pattern tree. Consequently, an online transaction of a user is compared with the profile of the user, so that any anomaly can be effectively detected.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.99-100
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• 2006

Silicon-on-insulator(SOI) MOSFET with SiGe/Si heterostructure channel is an attractive device due to its potent use for relaxing several limits of CMOS scaling, as well as because of high electron and hole mobility and low power dissipation operation and compatibility with Si CMOS standard processing. SOI technology is known as a possible solution for the problems of premature drain breakdown, hot carrier effects, and threshold voltage roll-off issues in sub-deca nano-scale devices. For the forthcoming generations, the combination of SiGe heterostructures and SOI can be the optimum structure, so that we have developed SOI n-MOSFETs with SiGe/Si heterostructure channel grown by reduced pressure chemical vapor deposition. The SOI n-MOSFETs with a SiGe/Si heterostructure are presented and their DC characteristics are discussed in terms of device structure and fabrication technology.

• Journal of Chest Surgery
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• v.29 no.8
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• pp.916-922
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• 1996

In patients with pleural adhesion, video-assisted thoracic surgery (VATS) has been regarded as a contra- indication. When such adhesions were found during a thoracoscopic trial, the thoracotomy proceeded with for fear of parenchymal Injury and bleeding. We had a question whether or not thoracoscopic surgery should be done in such pleural adhesions. Of the 226 consecutive thoracoscopic surgeries from Jul. 1992 through Sep. 1995, pleural adhesions were detected intraoperatively in 50 cases (22.1%): a detailed breakdown is as follows: pneumothorax (16 cases), pleural disease (15), benign pulmonary nodule(7), mediastinal mass(5), hyperhidrosis (2), diffuse parenchymal or interstitial lung disease (2), bronchiectasis(2), and primary lung cancer(1). We classified pleural adhesions according to their extent and severity. Extent is categorized as the involved area of the lung: degree 1, II, or III; severity is given one of four grades: mild, moderate, severe, or ve y severe. In cases of very severe severity requiring decortication, the possibility of VATS was excluded. Of the 50 cases, mild adhesions were detected in 15 cases(30.0%), moderate in 29 (58.0%), and severe in 6 (12.0%). As for the extent of the adhesions, 8 cases (16.0%) were categorized as degree 1, 32 cases (64. 0%) as degree II, and 10 cases (20.0%) as degree III. For patients with pleural adhesions, the operation time, the chest tube indwelling time, and the postoperative hospital stay were all longer than for patients in the non-adhesion group. Postoperative complications, namely prolonged air-leakage and pleural drain- age, were more common (18.0% and 6.0%, respectively) than in the non-adhesion group (5.1% and 1.7%, respectively). Only two bronchiectatic patients (4%) were converted to an open thoracotomy because of in- ability to control bleeding. Although complications were encountered more frequently in the group with adhesions, patients were still able to enjoy the benefi s of thoracoscopic surgery. It is advisable to proceed with thoracoscopic surgery even in cases of unpredicted pleural adhesions.