• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.2
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• pp.277-282
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• 2017

Nickel germanide (NiGe) is one of the most promising alloy materials for source/drain (S/D) of Ge MOSFETs. However, NiGe has limited thermal stability up to $450^{\circ}C$ which is a challenge for fabrication of Ge MOSFETs. In this paper, a novel method is proposed to improve the thermal stability of NiGe using Co interlayer. As a result, we found that the thermal stability of NiGe was improved from $450^{\circ}C$ to $570^{\circ}C$ by using the proposed Co interlayer. Furthermore, we found that current-voltage (I-V) characteristic was improved a little by using Co/Ni/TiN structure after post-annealing. Therefore, NiGe formed by the proposed Co interlayer that is, Co/Ni/TiN structure, is a promising technology for S/D contact of Ge MOSFETs.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1174-1177
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• 2006

A bottom contact organic thin film transistor (OTFT) is fabricated with an organic double-layered gate insulator (GI) and pentacene. The PMMA and MNB layers are treated on gate insulator and source/drain (S/D, Au) before depositing pentacene to investigate device properties and pentacene growth. The sequence of surface treatment affects a device performance seriously. The ultra-thin PMMA (below 50A) was deposited on organic gate insulator and S/D metal by spin coating method, which showed no deterioration of on-state current (Ion) although bottom contact structure was exploited. We proposed that the reason of no contact resistance (Rc) increase may be due to a wettability difference in between PMMA / Au and PMMA / organic GI. As a result, the device treated by $PMMA\;{\rightarrow}\;MNB$ showed much better Ion behavior than those fabricated by $MNB\;{\rightarrow}\;PMMA$. We will report the important physical and electrical performance difference associated with surface treatment sequence.

• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.289-292
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• 2012

Au electrodes modified with self-assembled monolayers (SAMs) were used to control the work function of source/drain electrodes in triethylsilylethynyl anthradithiophene (TES ADT)-based organic thin film transistors (OTFTs). By using benzothiol (BT) and pentafluorobenzothiol (PFBT) SAMs, the hole injection barrier between Au and the highest occupied molecular orbital (HOMO) of TES ADT was controlled. After a solvent annealing, TES ADT OTFTs with PFBT SAM-treated Au electrodes were found to exhibit high field-effect mobilities of $0.05\;cm^2/Vs$ and on/off current ratios of $10^6$.

• Journal of electromagnetic engineering and science
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• v.15 no.2
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• pp.82-88
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• 2015

The magnetron, a vacuum tube, is currently the usual high-power microwave power source used for microwave heating. However, the oscillating frequency and output power are unstable and noisy due to the low quality of the high-voltage power supply and low Q of the oscillation circuit. A heating system with enhanced reliability and the capability for control of chemical reactions is desired, because microwave absorption efficiency differs greatly depending on the object being heated. Recent studies on microwave high-efficiency power amplifiers have used harmonic processing techniques, such as class-F and inverse class-F. The present study describes a high-efficiency 100 W GaN-HEMT amplifier that uses a harmonic processing technique that shapes the current and voltage waveforms to improve efficiency. The fabricated GaN power amplifier obtained an output power of 50.4 dBm, a drain efficiency of 72.9%, and a power added efficiency (PAE) of 64.0% at 2.45 GHz for continuous wave operation. A prototype microwave heating system was also developed using this GaN power amplifier. Microwaves totaling 400 W are fed from patch antennas mounted on the top and bottom of the microwave chamber. Preliminary heating experiments with this system have just been initiated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4C
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• pp.371-379
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• 2002

In this paper, the MMIC SPST switches operating from DC to 3GHz were designed and implemented. Prior to the design of switches, the small and large-signal switch models were needed to predict switch performance accurately. The newly proposed small-signal switch model parameters were extracted from measured S-parameters using optimization technique with estimated initial values and boundary limits. In the extraction of large-signal switch model parameters, the current source was modeled by fitting empirical equations to measured DC data and the charge model was derived from extracted channel capacitances from measured S-parameters varying the drain-source voltage. To design basic series-shunt SPST switches and isolation-improved SPST switches, we applied this model to commercial microwave circuit simulator. The improved SPST switches exhibited 0.302dB insertion loss, 35.762dB isolation, 1.249 input VSWR, 1.254 output VSWR, and about 15.7dBm PldB with 0/-3V control voltages at 3GHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.149-150
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• 2006

A ZnO nanowire-based FET is fabricated m this study on a flexible substrate of PES. For the flat and bent flexible substrates, the current ($I_D$) versus drain-source bias voltage ($V_{DS}$) and $I_D$ versus gate voltage ($V_G$) results are compared. The flat band was Ion/Ioff ratio of ${\sim}10^7$, a transconductance of 179 nS and a mobility of ~10.104 cm2/Vs at $V_{DS}$ =1 V. Also bent to a radius curvature of 0.15cm and experienced by an approximately strain of 0.77 % are exhibited an Ion/Ioff ratio of ${\sim}10^7$, a transconductance of ~179 nS and a mobility of ${\sim}10.10 cm^2/Vs$ at $V_{DS}$ = 1V. The electrical characteristics of the FET are not changed very much. although the large strain is given on the device m the bent state.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.675-678
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• 2003

We studied the electrical characteristics of pentacene-based organic field-effect transistors (FETs) with polymethyl methacrylate (PMMA) or poly-4-vinylphenol (PVP) as the gate insulator. PMMA or PVP was spin-coated on the indium tin oxide glass substrate that serves as gate electrodes. The source-drain current dependence on the gate voltage shows the FET characteristics of the hole accumulation type. The transistor with PVP shows a higher field-effect mobility of 0.14 $cm^{2}/Vs$ compared with 0.045 $cm^{2}/Vs$ for the transistor with PMMA. The atomic force microscope (AFM) images indicate that the grain size of the pentacene on PVP is larger than that on PMMA. X-ray diffraction (XRD) patterns for the pentacene deposited on PVP exhibit a new Bragg reflection at $19.5{\pm}0.2^{\circ}$, which is absent for the pentacene on PMMA. This peak corresponds to the flat-lying pentacene molecules with less intermolecular spacing.

• Journal of Sensor Science and Technology
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• v.22 no.2
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• pp.105-110
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• 2013

We fabricated an a-IGZO thin film transistor (TFT) with AZO/Ag/AZO transparent multilayer source/drain contacts by rf magnetron sputtering. a-IGZO TFT with AZO/Ag/AZO multilayer S/D electrodes (W/L = 400/50 ${\mu}m$) showed a subs-threshold swing of 3.78 V/dec, a minimum off-current of $10^{-12}$ A, a threshold voltage of 0.41 V, a field effect mobility of $10.86cm^2/Vs$, and an on/off ratio of $9{\times}10^9$. From the ultraviolet photoemission spectroscopy, it was revealed that the enhanced electrical performance resulted from the lowering of the Schottky barrier between a-IGZO and Ag due to the insertion of an AZO layer and thus the AZO/Ag/AZO multilayer would be very appropriate for a promising S/D contact material for the fabrication of high performance TFTs.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.4
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• pp.506-510
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• 2016

A triple-band (TB) oscillator was implemented in the TSMC $0.18{\mu}m$ 1P6M CMOS process, and it uses a cross-coupled nMOS pair and two shunt $4^{th}$ order LC resonators to form a $6^{th}$ order resonator with three resonant frequencies. The oscillator uses the varactors for band switching and frequency tuning. The core current and power consumption of the high (middle, low)- band core oscillator are 3.59(3.42, 3.4) mA and 2.4(2.29, 2.28) mW, respectively at the dc drain-source bias of 0.67V. The oscillator can generate differential signals in the frequency range of 8.04-8.68 GHz, 5.82-6.15 GHz, and 3.68-4.08 GHz. The die area of the triple-band oscillator is $0.835{\times}1.103mm^2$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.5
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• pp.785-793
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• 2016

This paper analyzes an LCL-type isolated dc-dc converter operating for constant output voltage in the continuous conduction mode(CCM) with resistances of parasitic losses-static drain-source on resistance of power switch, ESR of resonant network(L-C-L)-using a high loaded quality factor Q assumptions and fourier series techniques. Simple analytical expressions for performance characteristics are derived under steady-state conditions for designing and understanding the behavior of the proposed converter. The voltage-driven rectifier is analyzed, taking into account the diode threshold voltage and the diode forward resistance. Experimental results measured for a proposed converter at low input voltage and various load resistances show agreement to the theoretical performance predicted by the analysis within maximum 4% error. Especially in the case of low output voltages and large loads, It is been observed that introduction of both rectifier and the parasitic components of converter had considerable effect on the performance.