Jin-Koo Rhee

Two-stage broadband high-gain W-band amplifier using 0.1-/spl mu/m metamorphic HEMT technology

We report broadband high-gain W-band monolithic microwave integrated circuit amplifiers based on 0.1-/spl mu/m InGaAs-InAlAs-GaAs metamorphic high electron mobility transistor (MHEMT) technology. The amplifiers show excellent S/sub 21/ gains greater than 10 dB in a very broad W-band frequency range of 75-100 GHz, thereby exhibiting a S/sub 21/ gain of 10.1 dB, a S/sub 11/ of -5.1 dB and a S/sub 22/ of -5.2 dB at 100 GHz, respectively. The high gain of the amplifier is mainly attributed to the performance of the MHEMTs exhibiting a maximum transconductance of 691 mS/mm, a current gain cutoff frequency of 189 GHz, and a maximum oscillation frequency of 334 GHz.

V-band CPW 3-dB Tandem coupler using air-bridge structure

We present a uniplanar coplanar waveguide 3-dB tandem coupler operating at V-band frequencies. The uniplanar structure is monolithically fabricated by using two-section parallel-coupled lines and air-bridge crossovers replacing the conventional multilayer or the bonded structures. Due to an optimized tandem structure and nonbonded crossovers minimizing the parasitic components, a maximum coupling of 2.5dB is measured at 62GHz with a 2-dB bandwidth of 83%, while a high directivity factor of 33dB is simultaneously obtained at 58-62GHz. Over the entire design frequency range of 30-90GHz, we achieve good phase unbalance of 90/spl plusmn/6.0/spl deg/, return loss, and isolation lower than -23 and -16dB, respectively.

Design of an RF low-noise bandpass filter using active capacitance circuit

In this paper, a novel RF active bandpass filter (BPF) is proposed and its noise performance is optimized by noise analysis. In the proposed design, a resonator consists of an active capacitance circuit together with a conventional inductor. The active capacitor is made of a field-effect transistor that exhibits negative resistance as well as capacitance. It can, therefore, compensate the loss of an inductor. Whereas the conventional active filters using negative resistance circuits usually have a high noise figure, the proposed active filter shows good noise property achieved by adopting a novel active capacitance circuit, which is proven by noise analysis and the experimental result. The measured second-order active BPF shows bandwidth of 95 MHz, 0.1-dB insertion loss, 0.3-dB ripple, and a noise figure of 2.4 dB at the 1.9-GHz band, which agrees well with the simulated results

An RF-MEMS Switch With Low-Actuation Voltage and High Reliability

In this paper, we report a novel radio-frequency (RF) microelectromechanical systems switch with low-actuation voltage and long lifetime by adopting a design approach in which a freely moving contact pad structure opens and closes the switch through electrostatic actuation. Unlike electrostatically actuated suspended beam or bridge contact pad structures, the freely moving contact pad can be reliably operated at a low-actuation voltage of 4.5 V because actuation energy is not used in elastic deformation of a suspension. At a frequency of 50 GHz, an insertion loss of 0.5 dB and an isolation of 55 dB were obtained from the switch. Measured delay times for switch-on and switch-off were 120 and 130 ns, respectively. After 200 billion cyclic actuations with signal RF power of 0 dBm by cold switching, actuation voltages remained the same; insertion loss and isolation were maintained below 0.59 and 54 dB, respectively; and delay times for switch-on and switch-off have no change at 50 GHz. However, when the switch slants to any direction over 28deg, the actuation voltage increases over 5 V because movement of the movable lower contact pad is obstructed by friction between the movable contact pad and the guard poles

94-GHz Log-Periodic Antenna on GaAs Substrate Using Air-Bridge Structure

We fabricated a compact, 94-GHz log-periodic planar antenna on GaAs substrate. We used millimeter-wave monolithic integrated circuit (MMIC) process technology to fabricate the on-chip antenna. An air-bridge crossover is used to replace the conventional bonded structure for crisscross connection, which is compatible with active devices and circuits. The fabricated antenna chip size is 1.2 times 2.6 mm2 . Measurement results show that this antenna can operate from 87 to 99.5 GHz with its return loss better than -10 dB. At 94 GHz, the log-periodic antenna has a return loss of -11 dB and 4.8 dBi of gain.

Small-Signal Analysis of High Maximum Frequency of Oscillation 0.1-µm Off-Set Gamma-Shaped Gate InGaAs/InAlAs/GaAs Metamorphic High-Electron-Mobility Transistors

We examined the effects of gate recess process conditions on the electrical characteristics of 0.1-µm-gate-length metamorphic high-electron-mobility transistors (MHEMTs) by the comparative analysis of small-signal parameters. When the wide-gate-recess method is adopted, significant reductions in gate-to-drain conductance and gate-to-drain capacitance were obtained compared with those obtained by the of narrow-gate-recess method. These differences in small-signal parameters are due to the removal of the entire n+ cap layer and corresponding dissimilarity in gate structure when the wide-gate-recess method is used. The wide-gate-recess method produced ~1/2 drain-source saturation current and extrinsic transconductance compared with the narrow-gate-recess method. In contract to the DC performances, a markedly enhanced S21 gain of 3.5 dB and an fmax of 447 GHz were obtained from the MHEMTs processed by the wide-gate-recess method. This high fmax is responsible for the proper selection of the gate recess method for what and is one of the best data thus far reported for 0.1-µm-gate-length MHEMTs.

Chemical mechanical polishing of shallow trench isolation using the ceria-based high selectivity slurry for sub-0.18 μm complementary metal–oxide–semiconductor fabrication

In this article we investigate the effects of chemical mechanical polishing using a CeO2-based high silicon-nitride/silicon-dioxide selectivity slurry on 0.18 μm complementary metal–oxide–semiconductor (CMOS) shallow trench isolation (STI). When high selectivity slurry (HSS) is employed for STI, within-die and lot-to-lot variations of the remaining pad nitride thickness and the field oxide erosion are significantly reduced to ∼150 and ∼400 A, respectively, which are much smaller than for cases of conventional silica-based slurry. Scratches occupy ∼80% of the total defect in the case of HSS STI polishing, and are minimized by using an optimized in situ filtering method for the slurry. When in situ filtered HSS is used, the gate oxide integrity of 256 million isolated MOS capacitors improves compared to samples prepared by conventional unfiltered HSS slurry. In addition, the level of leakage current for n+/p-well junctions is not affected when in situ filtered HSS is used for STI polishing.

94 GHz MMIC single balanced mixer for FMCW radar sensor application

We present a 94 GHz MMIC single balanced mixer using the branch line couplers and 0.1 μm GaAs-based metamorphic high electron mobility transistors (MHEMTs) for FMCW radar sensor application. The mixer was designed in a resistive structure because of no drain bias and low DC currents. Two single ended mixers in the fabricated MMIC single balanced mixer share gate bias circuits. The fabricated mixer shows a conversion loss of 14.7 dB at 94 GHz, and the LO to RF isolation of 34.2 ~ 35.2 dB in LO frequency range of 93.675 ~ 94.275 GHz.

A novel pull-up type RF MEMS switch with low actuation voltage

We report a novel pull-up type radio frequency (RF) microelectromechanical system (MEMS) switch with no elastic deformation of the cantilever involved in the actuation. At a voltage of 4.5V, reliable actuations are achieved such that the movable lower contact pad is pulled up by the electrostatic force to make contact with the upper pad. At a frequency of 50GHz, an insertion loss of 0.5dB, a return loss of 12.4dB, and an isolation of 55dB are obtained from the switch. The measured transient times for switch-on and switch-off are 120 and 130ns, respectively. Compared to the MEMS switches reported thus far, the pull-up type switch shows the best switching speed and isolation characteristic at 50GHz.

High switching performance 0.1-/spl mu/m metamorphic HEMTs for low conversion loss 94-GHz resistive mixers

We report high switching performance of 0.1-/spl mu/m metamorphic high-electron mobility transistors (HEMTs) for microwave/millimeter-wave monolithic integrated circuit (MMIC) resistive mixer applications. Very low source/drain resistances and gate capacitances, which are 56 and 31% lower than those of conventional pseudomorphic HEMTs, are due to the optimized epitaxial and device structure. Based on these high-performance metamorphic HEMTs, a 94-GHz MMIC resistive mixer was designed and fabricated, and a very low conversion loss of 8.2 dB at a local oscillator power of 7 dBm was obtained. This is the best performing W-band resistive field-effect transistor mixer in terms of conversion loss utilizing GaAs-based HEMTs reported to date.