S D Kim

Publications (5)6.45 Total impact

• Article: Millimeter-wave small-signal modeling with optimizing sensitive-parameters for metamorphic high electron mobility transistors

  S-W Moon, J-H Oh, Y-H Baek, M Han, J-K Rhee, S-D Kim
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  ABSTRACT: In this paper, we present a simple and reliable technique for determining the small-signal equivalent circuit model parameters of the 0.1 µm metamorphic high electron mobility transistors (MHEMTs) in a millimeter-wave frequency range. The initial eight extrinsic parameters of the MHEMT are extracted using two S-parameter (scattering parameter) sets measured under the pinched-off and zero-biased cold field-effect transistor conditions by avoiding the forward gate biasing. Furthermore, highly calibration-sensitive values of the Rs, Ls and Cpd are optimized by using a gradient optimization method to improve the modeling accuracy. The accuracy enhancement of this procedure is successfully verified with an excellent correlation between the measured and calculated S-parameters up to 65 GHz.
  Semiconductor Science and Technology 07/2010; 25(8):085002. · 1.72 Impact Factor
• Article: Effects of Si3N4 passivation on the dc and RF characteristics of metamorphic high-electron-mobility transistors depending on the gate-recess structures

  J H Oh, M Han, Y H Baek, S W Moon, J K Rhee, S D Kim
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  ABSTRACT: Effects of the Si3N4 passivation on the dc and RF characteristics of a 0.1 µm metamorphic high-electron-mobility transistor (HEMT) are investigated for narrow and wide gate-recess structures. Maximum drain-source saturation current (Idss,max) and maximum extrinsic transconductance (gm,max) are reduced by ~14.8 and ~11.6%, respectively, in the wide gate-recess structure after the passivation; on the other hand, only ~5.7 and ~4.9% reductions are measured from Idss,max and gm,max, respectively, in the narrow gate-recess structure. We examine the passivation-induced degradation by using a modified charge control model assuming the charged surface states on the Si3N4 interface and a comparative study of the hydrodynamic device simulation with the experimental measurement. From the analysis, it is proposed that the difference of degradation in two different gate structures is due to an approximately three times higher charged surface state density of ~4.5 × 1011 cm−2 in the wide gate-recess structure than ~1.6 × 1011 cm−2 in the narrow gate-recess structure. The cut-off frequency (fT) of the wide gate-recess structure also exhibits a greater reduction of ~14.5%, while the fT of the narrow gate-recess structure is reduced by only ~6.6% after the passivation. This is mainly due to the passivation-induced surface states of a higher density in the wide gate-recess structure. A great increase of the gate-to-drain parasitic capacitance in the wide gate-recess structure makes a major contribution to ~13.5% degradation of the maximum frequency of oscillation.
  Semiconductor Science and Technology 01/2009; 24(2):025027. · 1.72 Impact Factor
• Conference Proceeding: 94 GHz Waveguide VCO with Magic_T for FMCW radar

  D.S. Ko, S.W. Moon, M.K. Lee, S.J. Lee, Du Hyun Ko, S.H. Bang, Y.H. Baek, M. Han, S.G. Choi, T.J. Baek, S.D. Kim, J.K. Rhee
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  ABSTRACT: In this paper, we have designed and fabricated the waveguide voltage controlled oscillator (VCO) at 94 GHz, which consists of a GaAs Gunn diode, a varactor diode, and two bias posts with low pass filter (LPF), and a Magic Tee for FMCW radar. The cavity is designed for a fundamental mode at 47 GHz and operated at second harmonic of 94 GHz center frequency. The fabricated VCO has 640 MHz bandwidth, 505 MHz linearity with 2%. The VCO operates at 93.9 GHz with phase noise of -102.79 dBc/Hz at 1 MHz offset and power of 11.34 dBm. The W-band VCO has phase noise better than -100 dBc/Hz.
  Microwave Conference, 2008. EuMC 2008. 38th European; 12/2008
• Article: TEM Observation of Electron-Beam Induced Phase Transformation of Al7Cu2Fe

  D-S  Ko , S-D  Kim , WK  Jang , KS  Shin , Y-W  Kim 
  Microscopy and Microanalysis 07/2007; 13:1096 - 1097. · 3.01 Impact Factor
• Conference Proceeding: Design guide of coupling between inductors and its effect on reverse isolation of a CMOS LNA

  C.S. Kim, M. Park, C.-H. Kim, M.-Y. Park, S.-D. Kim, Y.-S. Youn, J.-W. Park, S.-H. Han, H.K. Yu, H. Cho
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  ABSTRACT: To establish the design guide on coupling between inductor pairs, we measured the magnitude of the electromagnetic coupling between inductors with the variation of physical separation and substrate resistivity. We also found that the coupling effect degrades the reverse isolation of L-band CMOS LNAs, and analyzed several LNAs fabricated with different fabrication technology. Furthermore, we proposed inductors for preventing the coupling, and its coupling reduction effect on the LNA is demonstrated
  Microwave Symposium Digest. 2000 IEEE MTT-S International; 02/2000