• Journal of IKEEE
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• v.13 no.4
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• pp.23-27
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• 2009

Ohmic contact formation and etching processes for the fabrication of MBE (molecular beam epitaxy) grown GaSb-based p-channel HEMT devices on Si substrate have been studied. Firstly, mesa etching process was established for device isolation, based on both HF-based wet etching and ICP-based dry etching. Ohmic contact process for the source and drain formation was also studied based on Ge/Au/Ni/Au metal stack, which resulted in a contact resistance as low as $0.683\;{\Omega}mm$ with RTA at $320^{\circ}C$ for 60s. Finally, for gate formation of HEMT device, gate recess process was studied based on AZ300 developer and citric acid-based wet etching, in which the latter turned out to have high etching selectivity between GaSb and AlGaSb layers that were used as the cap and the barrier of the device, respectively.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.353-356
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• 2000

Multi-bias parameter extraction technique for HEMT small signa] equivalent circuits is presented in this paper. The technique in this paper uses S-parameters measured at various bias points in the active region to construct one optimization problem, of which the vector of unknowns contains only a set of bias-independent elements. Tests are peformed on measured S-parameters of a pHEMT at 30 bias points. Results indicate that the calculated S-parameters is similar to the measured data.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.7 s.110
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• pp.659-664
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• 2006

This paper reports a high power 60 GHz push-push oscillator fabricated using $0.12{\mu}m$ metamorphic high electron-mobility transistors(mHEMTs). The devices with a $0.12{\mu}m$ gate-length exhibited good DC and RF characteristics such as a maximum drain current of 700 mA/mm, a peak gm of 660 mS/mm, an $f_T$ of 170 GHz, and an $f_{MAX}$ of more than 300 GHz. By combining two sub-oscillators having $6{\times}50{\mu}m$ periphery mHEMT, the push-push oscillator achieved a 6.3 dBm of output power at 59.5 GHz with more than - 35 dBc fundamental suppression. The phase noise of - 81.5 dBc/Hz at 1 MHz offset was measured. This is one of the highest output power obtained using mHEMT technology without buffer amplifier, and demonstrates the potential of mHEMT technology for cost effective millimeter-wave commercial applications.

• ETRI Journal
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• v.26 no.4
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• pp.307-314
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• 2004

The application of a discrete pseudomorphic high electron mobility transistor (p-HEMT) as a grounded switch allows for the development of low cost phase shifters and phase modulators operating in a Ku band. This fills the gap in the development of phase control devices comprising p-i-n diodes and microwave monolithic integrated circuits (MMICs). This paper describes a discrete p-HEMT characterization and modeling in switching mode as well as the development of a low-cost four-bit phase shifter and direct quadrature phase shift keying (QPSK) modulator. The developed devices operate in a Ku band with parameters comparable to commercially available MMIC counterparts. Both of them are CMOS compatible and have no power consumption. The parameters of the QPSK modulator are very close to the requirements of available standards for satellite earth stations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.5
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• pp.863-871
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• 2003

In this paper, we design a high stable Ku-band phase-locked dielectric resonant microwave oscillator with the gate voltage controls of p-HEMT. By adapting the nonlinear equivalent elements which affects phase noise of microwave oscillator, we optimize the nonlinear elements of p-HEMT to have low phase noise operation. Using the scattering parameters according to bias voltages, we designed the gate voltage control microwave dielectric resonant oscillator and phase-locked loop circuits is applied to have the high stable operations. Designed microwave oscillator as a local oscillator of digital microwave communication shows that output power is 9.17dBm at 10.75GHz and it's phase noise is -88dBc/Hz at 10KHz offset frequency.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.3917-3922
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• 2010

In this paper, 3 stage amplifier MMIC was designed and fabricated with U-band optimized epitaxal pHEMT that produced by large signal characterization and modeling for 60 GHz band. The pHEMT used in this paper, the gate $0.12\;{\mu}m$ length and total gate width of $100\;{\mu}m$, $200\;{\mu}m$ has been modeled using the large signal designed with negative feedback and MCLF instead of MIM capacitor for improving stability. Fabricated MMIC $2.5{\times}1.5mm^2$ size, current about 40 mA, operating frequency 59.5~60.5 GHz, gain 19.9~18.6 dB, input matching characteristics -14.6~-14.7 dB, output matching characteristics -11.9~-16.3 dB and output -5 dBm characteristics were obtained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2A
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• pp.201-206
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• 2006

A SPST Switch MMIC which used for Microwave Switch Matrix(MSM) of communications satellite payload with multi-beam function has been designed and fabricated. New RE FET switch configuration has been devised to improve power characteristics and isolation. Input and output return losses are better than another switches reported previously for both On and Off states. The MMIC chips were fabricated in 0.15um GaAs pHEMT process and measured insertion loss less than 2.0dB and isolation more than 63dB in the frequency range of 3GHz$\∼$4GHz. Output 3rd order interceptpoint above 32dBm has been recorded and the value is very high even though the unit pHEMT has gate width of 0.2mm and only four pHEMT are used in the MMTC.

• Journal of electromagnetic engineering and science
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• v.17 no.3
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• pp.147-152
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• 2017

This paper presents a frequency doubler operating at G-band that exceeds the maximum oscillation frequency ($f_{max}$) of the given transistor technology. A common-source transistor is biased on class-B to obtain sufficient output power at the second harmonic frequency. The input and output impedances are matched to achieve high output power and high return loss. The frequency doubler is fabricated in a commercial 150-nm GaAs pHEMT process and obtains a measured conversion gain of -5.5 dB and a saturated output power of -7.5 dBm at 184 GHz.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.87-90
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• 2005

High-efficiency switched-mode circuits such as the class-E amplifier are well-known in the MHz frequency range. The class-E amplifier is a type of switching mode amplifier offering very high efficiency approaching 100%. In this paper of the class-E amplifier by using pHEMT device, the design has been done theoretically and experimentally, with simulation by using the harmonic balance method using circuit simulator. The amplifier using microstrip circuit and the pHEMT demonstrate 66% power-added- efficiency (PAE) at 2.4GHz with 17.6dBm of output power.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.197-200
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• 2001

본 논문에서는 병렬귀환 유전체 발진기를 P-HEMT 게이트단의 바이어스 진압을 제어시켜 안정된 위상동기신호가 나타나도록 P-HEMT 게이트 바이어스 튜닝에 의한 Ku-band 고안정 위상동기 마이크로파 발진기를 설계하였다. 위상동기방식은 외부에서 제공되는 125MHz의 기준주파수를 SRD로 체배시켜 하모닉 신호를 이용한 마이크로파 샘플링 위상검파 방식으로 설계하였으며, 고안정 특성과 저위상잡음을 나타내는 위상동기 마이크로파 발진기(phase locked microwave oscillator)를 바랙터 다이오드를 사용하지 않고 P-HEMT의 게이트단을 동조시키는 방식으로 위상동기 발진기를 설계하고 게이트 바이어스에 따른 위상잡음 관계를 분석하였다