Papers by Author: In Ho Kang

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Authors: In Ho Kang, Sung Jae Joo, Wook Bahng, Sang Cheol Kim, Nam Kyun Kim
Abstract: The 50W Quasi-resonant mode SMPS which adopted a normally-on-type SiC JFET as a switch has been designed and characterized. A simple decision circuit and an auxiliary power supply was utilized to safely protect the JFET from an in-rush current at initial operation stage and to provide sufficient negative voltage for a complete JFET drive. Even without a refine engineering, the SMPS showed 96% efficiency at a full load state.
Authors: In Ho Kang, Jae Yeol Song, Sung Jae Joo, Wook Bahng, Sang Cheol Kim, Nam Kyun Kim
Abstract: The effect of the doping concentration and space of both p-grid and FLR on the electrical performances of 4H-SiC JBS diode has been investigated. A 4H-SiC JBS diode with the p-grid space of 3um, the FLR space of 3um, and the doping concentration of 5E18cm-3 showed the highest blocking voltage of 1500V.
Authors: S.J. Kim, S. Kim, Sang Cheol Kim, In Ho Kang, K.H. Lee, T. Matsuoka
Abstract: We have investigated the field limiting ring (FLR) geometry dependence of breakdown voltage characteristics for a junction barrier Schottky (JBS)-assisted FLR SiC-SBD. The SiC-SBDs having a guard ring-assisted FLR surrounding a Schottky contact edge and an internal ring inside Schottky contact were fabricated. The breakdown voltage characteristics of the JBS-assisted FLR SiC-SBD are significantly dependent on the width, spacing, and number of FLR. The breakdown voltage characteristic is improved as either the FLR width and FLR number increase or the FLR spacing decreases. Approximately 1650 V maximal breakdown voltage, corresponding to 82% ideal breakdown voltage, is observed with seven FLRs having 5 2m width and 1 2m spacing.
Authors: Moonkyong Na, In Ho Kang, Jeong Hyun Moon, Wook Bahng
Abstract: Nickel (Ni) is the most widely used metal for the formation of ohmic contact on n-type SiC. However, the irregular contact can potentially cause degradation in the device performance. To form the uniform ohmic interface, titanium (Ti) was applied as a barrier layer. Ni/Ti/SiC and Ti/Ni/SiC contact metal structures were prepared, and ohmic contacts were formed using a rapid thermal annealing process. The interfacial properties of both contact metal structures were enhanced by applying the Ti layer. The specific contact resistance of ohmic contacts showed a slightly lower or similar value (~ low 105 Ωcm2) compared with the specific contact resistance values formed from only the Ni contact metal.
Authors: Hyun Jin Jung, Seung Bok Yun, In Ho Kang, Jeong Hyun Moon, Won Jeong Kim, Wook Bahng
Abstract: The influence of stacking faults (SFs) and triangular defects (TDs) on the electrical properties of 4H-SiC Schottky barrier diode (SBD) were investigated. The SF types and locations were distinguished and mapped by using room-temperature photoluminescence (PL) and optical microscope. SBDs were fabricated including the location of SF’s and TD’s. The effects of the types of defects and its area portion in the fabricated SBDs were also investigated. Based on the present data, 3C-TD has more harmful effect rather than the other SFs. The fabricated SBDs including SFs showed that increase of area portion of SF’s also resulted increase of specific on resistance of SBDs.
Authors: Wook Bahng, Hui Jong Cheong, In Ho Kang, Seong Jin Kim, Sang Cheol Kim, Sung Jae Joo, Nam Kyun Kim
Abstract: We have investigated the influence of surface modification on the electrical properties of SiC diodes. Schottky diodes (SBDs) as well as PiN diodes were fabricated on n-type SiC substrate with an epilayer, and electrically characterized before and after high temperature annealing, and after removing the surface modified layer, respectively. The devices annealed without graphite cap layer showed ohmic behavior. The surface layer was modified to a conductive layer possibly due to the preferred sublimation of Si species. In order to confirm the existence of modified surface conductive layer, diode was fabricated on the same substrate and electrically characterized after removing 30nm-thick damaged layer by ICP-RIE. The leakage current reduced dramatically, as much as 7 orders of magnitude. The PiN diodes fabricated on the damaged surface layer showed the reverse leakage current and the breakdown voltage of 50mA and 1250V, respectively. While those of the diode fabricated after removing the damaged surface layer were 200nA at the breakdown voltage of 2100V, respectively.
Authors: In Ho Kang, Wook Bahng, Sang Cheol Kim, Sung Jae Joo, Nam Kyun Kim
Abstract: A double delta-doped channel 4H-SiC MESFET is proposed to kick out degradation of the DC and RF performances caused by the surface traps, by forming a quantum-well-like potential well and separating an effective channel from the surface. To obtain an optimum device structure, the DC and RF performances of double delta-doped channel MESFETs having various delta-doping concentrations but the same pinch-off voltage with that of conventional MESFET were also investigated. The SilvacoTM simulation results show that the double delta-doped channel MESFET achieved more improvement of the drain current, the cut-off frequency, and the maximum oscillation frequency for higher delta-doping concentration near the gate. In all cases, DC and RF performances for double delta-doped channel MESFETs are much improved than those of the conventional MESFET.
Authors: In Ho Kang, Wook Bahng, Sung Jae Joo, Sang Cheol Kim, Nam Kyun Kim
Abstract: The effects of post annealing etch process on electrical performances of a 4H-SiC Schottky diodes without any edge termination were investigated. The post etch was carried out using various dry the dry etch techniques such as Inductively Coupled Plasma (ICP) and Neutral Beam Etch (NBE) in order to eliminate suspicious surface damages occurring during a high temperature ion activation process. The leakage current of diodes treated by NBE measured at -100V was about one order lower than that of diode without post etch and a half times lower than that of diode treated by ICP without a significant degradation of forward electrical characteristics. Based on the above results, the post annealing process was adapted to a junction barrier Schottky diode with a field limiting ring. The blocking voltages of diode without post annealing etch and diodes treated by ICP and NBE were -1038V, -1125V, and -1595V, respectively.
Authors: Wook Bahng, Hui Jong Cheong, In Ho Kang, Sang Cheol Kim, Ki Hyun Kim, Nam Kyun Kim
Abstract: The initial homoepitaxial growth behavior on nearly on-axis 4H-SiC substrates was investigated. We have observed circular etch pits on the surface of on-axis substrate in the presence of source gases. However, there were no circular etch pits on the surface of off-axis substrates. In addition, the surface etched by H2 gas did not show circular etch pits even on nearly on-axis substrates. The shape of the circular etch pits was similar to spiral one. The initial growth behavior of epilayers was also investigated with various C/Si ratios of source gases (0.6
Authors: Ki Hyun Kim, Ye Hwan Kang, Jung Hun Lee, Eun Sik Jung, In Ho Kang, Chang Heon Yang
Abstract: In this paper, to verify implant effect characteristics variation by stripe type, grid type and circle type, the P+ implant patterning was studied. The result of two-dimensional simulation was controlled by adjusting the relative area of Schottky and p–n junction dimensions of the device, which is easily implemented during the device layout design. 4H-SiC JBSs with three types have been successfully fabricated and breakdown voltage in the range of 1694–2051 V has been achieved. The results of fabricated JBSs, show that the stripe type JBSs combine the best features of the P+ implant patterns.
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