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Ching-Sung Lee,Bo-I Chou,Wei-Chou Hsu,Ke-Hua Su 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6
This work reports a novel AlGaAs/InGaAsN/GaAs heterostructure field-eect transistor (HFET) by integrating a dilute In0:3Ga0:7AsN0:01 nitride-channel directly onto a GaAs substrate by using a molecular beam epitaxy (MBE) system. Introducing nitrogen doping into an In0:3Ga0:7As channel can effectively reduce the eective energy band gap, resulting in an improved electron confinement capability. The thermal threshold coeficient (∂Vth=∂T) is very low, -1.07 mV/K, with an improved high-temperature linearity (∂GV S=∂T) of only 0.33 mV/K. Besides, improved high-temperature device characteristics have been achieved at 450 (300) K, including a gate-voltage swing (GVS) of 1.15 (1.2) V, a two-terminal gate-drain breakdown voltage (BVGD) of -14.4 (-15.8) V and a turn-on voltage (Von) of 0.92 (1.147) V.
Ching-Sung Lee,Dong-Hai Huang,Jun-Chin Huang,Ke-Hua Su,Wei-Chou Hsu,Yeong-Jia Chen 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.48 No.4
A -doped In0.45Al0.55As/In0.53Ga0.47As/InAlGaAs/GaAs metamorphic high electron mobility transistor (MHEMT) using a Ni/Au-gate electrode has been successfully fabricated and demonstrated. Compared to conventional Au-gate devices with identical structures, the proposed device improves the kink-effect-related output conductance, the gate-voltage swing, the current drive capability, the breakdown characteristics, and the device power performance. Experimentally, a high extrinsic transconductance of 309 mS/mm, a high drain-source saturation current density of 573 mA/mm, an improved gate-voltage swing of 1.05 V with a corresponding saturation current density of 314 mA/mm, a high saturated output power of 11.3 dBm, and a high power gain of 23.8 dB with a power-added efficiency of 39.2 % are obtained for a 0.65 × 200 μm2 gate at 300 K. In addition, the measured fT and fmax are 49.1 and 61.7 GHz, respectively.
Ching-Sung Lee,Chia-Jeng Chian,Wei-Chou Hsu,Ke-Hua Su,Su-Jen Yu 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.4
This work provides comprehensive comparisons of the device characteristics, including the voltage gain, power performance, linearity and noise characteristics, for InAlAs/InGaAs/GaAs metamorphic high electron mobility transistors with respect to different indium contents in the InGaAs channel. Though the device with a high In-ratio InGaAs channel usually demonstrated improved high-frequency characteristics, the kink effects in their narrow-gap channel materials were found to seriously degrade the device performance. On the other hand, the low In-ratio channel device had characteristics advantageous for high-gain and high-linearity applications while the device with a compromised channel composition design was suitable for high-power circuit applications. This work provides comprehensive comparisons of the device characteristics, including the voltage gain, power performance, linearity and noise characteristics, for InAlAs/InGaAs/GaAs metamorphic high electron mobility transistors with respect to different indium contents in the InGaAs channel. Though the device with a high In-ratio InGaAs channel usually demonstrated improved high-frequency characteristics, the kink effects in their narrow-gap channel materials were found to seriously degrade the device performance. On the other hand, the low In-ratio channel device had characteristics advantageous for high-gain and high-linearity applications while the device with a compromised channel composition design was suitable for high-power circuit applications.
Investigations of δ -Doped In0.52Al0.48As/InxGa1-xAs/InP HEMTs with Different Channel Structures
Ching-Sung Lee,Hsin-Hung Chen,Jun-Chin Huang,Wei-Chou Hsu,Yeong-Jia Chen 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.47 No.6
The device characteristics of -doped In0.52Al0.48As/InGaAs/InP high-electron-mobility transistors (HEMTs) with different channel designs, grown by using the low-pressure metal-organic chemical-vapor deposition (LP-MOCVD) technique, have been studied. The InxGa1.xAs channel structures include a step-graded channel (SGC) with x = 0.56/0.53/0.5, a lattice-matched channel (LMC) with x = 0.53, and an inverse linearly-graded channel (ILGC) with x = 0.5 ! 0.56. Improvements in the device’s threshold, extrinsic conductance, saturation current density, gate-voltage swing (GVS), output conductance, voltage gain, and high-frequency and high-temperature performances have been comprehensively investigated and compared with respect to the specific channel design.
Chou, Yi-Hsuan,Choo, Kwang-Ho,Chen, Shiao-Shing,Yu, Jui-Hsuan,Peng, Ching-Yu,Li, Chi-Wang Elsevier 2018 Separation and purification technology Vol.198 No.-
<P><B>Abstract</B></P> <P>A chemical reduction process was proposed to recover copper from the retentate of polyelectrolyte enhanced ultrafiltration (PEUF). Three polyelectrolytes (PSS, PAA, and PEI) containing various functional groups and molecular weights were studied to explore their effects on the copper removal in PEUF and on the copper recovery by chemical reduction under various pH conditions. With PSS which contains sulfonic group, copper was removed reasonably well (ca. 75%) by PEUF even under acidic pH value of 3. With PAA which contains carboxylic group, copper removal was a bit low (∼60%) under pH 3.0 but increased substantially at pH 4.0. A branched PEI having amine group achieved the highest Cu removal of 94% at pH 3. The copper removal efficiency decreased slightly with increasing pH due to the high permeation of PEI through membrane.</P> <P>Chemical reduction achieved the complete copper recovery for solution containing PSS. The copper recovery efficiencies were more than 95% for PAA solution with pH values ranging from 3 to 9 at reaction time of one hour. For PEI, the recovery efficiencies ranged from 20 to 96% and were pH dependent. Aggregated and settled readily copper particles were produced by chemical reduction in PSS solution. XRD analysis identified cuprous oxide in all of the samples. Dependent of pH and polyelectrolytes, additional peaks matching those of elemental copper were identified. TGA analysis showed that solids produced from PSS and PAA systems contained no polyelectrolytes while solid collected from PEI system contained 32% of polyelectrolyte.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Polyelectrolytes with different functional groups and MW were applied in PEUF. </LI> <LI> Effects of polyelectrolytes and pH on the reduction of copper were studied. </LI> <LI> Both Cu<SUB>2</SUB>O and Cu<SUP>0</SUP> were identified by XRD analysis of solids obtained. </LI> </UL> </P>