• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.12
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• pp.130-135
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• 1995

GaAs power MESFET's with 0.5 .mu.m gate length using a conventional UV lithography and angle evaporations are fabricated and then DC and RF characteristics are measured and carefully analyzed. The 0.5$\mu$m GaAs power MESFET's are fabricated on epi-wafers which have an undoped GaAs layer inbetween n+ and n GaAs layers grown by MBE, and by the processes such as an image reversal(IR), air-bridge, and our developed 0.5 .mu.m gate fabrication techniques. The total gate widths of the fabricated 0.5$\mu$m GaAs power MESFETs are 0.6-3.0 mm, the current saturation of them 80-400 mA, the maximum linear and RF output power of them 60-265 mW. The current gain cut-off frequencies for the 0.5$\mu$m GaAs power MESFETs varies 13-16 GHz. For the test frequency of 10 GHz the maximum unilateral transducer power gains and the power added efficiencies of the GaAs power devices are 7.0-2.5 dB and 35.68-30.76 %, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11A
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• pp.1104-1109
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• 2005

In this paper, a Ka-band harmonic mixer is designed and fabricated on the base of the multiplier theory that there is a bias point to maximize the third harmonic order($3f_{LO}$) with respect to a fundamental LO frequency($f_{LO}$), which can make the high-order mixing element($f_{RF}{\pm}3f_{LO}$) to be greater than other mixing elements, Pumping a RF frequency($f_{RF}$) and LO frequency($f_{LO}$). The harmonic mixer by the proposed design method is fabricated by using a commercial GaAs MESFET device with a plastic package and overcome these disadvantages that a conventional mixer in Ka-band suffer from a high cost, inefficient productivity and circuit complexity. The harmonic mixer have a -10 dB conversion loss at the IF Sequency($3f_{LO}-f_{RF}$=1.0GHz) by selecting a gate bias voltage for the maximum third-order LO harmonic element($3f_{LO}$=34.5 GHz) as pumping LO frequency($f_{LO}$=11.5 GHz) With respect to RF Sequency ($f_{RF}$=33.5GHz)

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.10
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• pp.678-686
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• 2001

Origins for the transconductance dispersion and the gate leakage current in a GaAs metal semiconductor field effect transistor were found using capacitance deep-level transient spectroscopy (DLTS) measurements. In DLTS spectra, we observed two surface states with thermal activation energies of 0.65 $\times$ 0.07 eV and 0.88 $\times$ 0.04 eV and an electron trap EL2 with thermal activation energy of 0.84 $\times$ 0.01 eV. Transconductance was decreased in the frequency range of 5.5 Hz ~ 300 Hz. The transition frequency shifted to higher frequencies with the increase of temperature and the activation energy for the change of the transition frequency was determined to be 0.66 $\times$ 0.02 eV. From the measurements of the gate leakage current as a function of the device temperature, the forward and reverse currents are coincident with each other below gate voltages lower than 0.15 V, namely Ohmic behavior between gate and source/drain electrodes. The activation energy for the conductance of electrons on the surface of MESFET was 0.63 $\times$ 0.01 eV. Comparing activation energies obtained by different measurements, we found surface states H1 caused the transconductance dispersion and the fate leakage current.