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Chiu H.-C.,Chang Gung University | Wang H.-C.,Chang Gung University | Yang C.-W.,Chang Gung University | Hsin Y.-M.,National Central University | And 3 more authors.
IEEE Transactions on Device and Materials Reliability | Year: 2014

This work develops a thermally stable micromachined AlGaN/GaN high-electron mobility transistor (HEMT) with an enhanced breakdown voltage. After removal of the Si substrate beneath the HEMT, a 300-nm SiO2 and a 20- μm copper layer are deposited to form the GaN-on-insulator (G.O.I.) structure. The self-heating at high current that is exhibited by GaN HEMTs that are by previously developed full substrate removal methods is eliminated. The need for complicated substrate-transfer technology is also eliminated, increasing chip package yield. The low frequency noise measurement results also demonstrate that the trap density of the buffer/transition layer is reduced by the removal of the substrate and micromachining of the HEMTs. © 2001-2011 IEEE.


Hsu W.-C.,Institute of Microelectronics | Lee C.-S.,Feng Chia University | Ho C.-S.,Institute of Microelectronics | Lai Y.-N.,Institute of Microelectronics | And 5 more authors.
Electrochemical and Solid-State Letters | Year: 2010

This article reports an InAlAs/InGaAs metal oxide semiconductor metamorphic high electron mobility transistor (MOS-MHEMT) by using ozone water oxidation treatment to form an 8.5 nm thick gate oxide with a superior surface flatness. The proposed MHEMT with (without) ozone treatment has demonstrated a lower gate leakage density of 2μA/mm (0.48 mA/mm) at Vgd =-5 V, improved output conductance (gd) of 8.5 (33.1) mS/mm, gate-voltage swing of 0.9 (0.45) V, enhanced output power of 18.34 (13.43) dBm, and power-added efficiency of 46.8 (26.3)% at 300 K, with gate dimensions of 1×200 μm2. © 2010 The Electrochemical Society.


Lee C.-S.,Feng Chia University | Chou B.-Y.,National Cheng Kung University | Yang S.-H.,Feng Chia University | Hsu W.-C.,National Cheng Kung University | And 6 more authors.
IEEE Transactions on Electron Devices | Year: 2011

A novel Γ-gate Al0.24Ga0.76As/In 0.15Ga0.85As metal-oxide-semiconductor (MOS) high-electron-mobility transistor (MOS-HEMT) by using methods of ozone water oxidation and shifted exposure has been comprehensively investigated. Effective gate-length reduction, improved gate insulation, and formations of a field plate and a full surface passivation within the drain-source region are simultaneously achieved. The present Γ-gate MOS-HEMT has demonstrated superior device performances, including improvements of 523% (12.8%) in two-terminal gate-drain breakdown, 137% (36.1%) in on-state drain-source breakdown, 16.1% (11.8%) in maximum extrinsic transconductance (g m, max), 34.5% (9.7%) in intrinsic voltage gain (AV), 27.8% (16.2%) in power-added efficiency, 34.5% (19.8%) in minimum noise figure (NFmin) , and 28%/39.3% (11.4%/21.6%) in unity-gain cutoff frequency/maximum oscillation frequency (fT/fmax), as compared to a conventional Schottky-gate (MOS-gate) device fabricated upon the same epitaxial structure by using an identical optical mask set. Investigations of optimum extracted parasitics, small-signal device parameters, and high-temperature device characteristics at 300 K-450 K are also made in this work. © 2006 IEEE.


Lee C.-S.,Feng Chia University | Hsu W.-C.,Institute of Microelectronics, Singapore | Hsu W.-C.,National Cheng Kung University | Chou B.-Y.,Institute of Microelectronics, Singapore | And 7 more authors.
IEEE Transactions on Electron Devices | Year: 2015

Comparative studies for TiO2-passivated Al0.25Ga0.75N/GaN heterostructure FETs (HFETs) and TiO2-dielectric MOS-HFETs using nonvacuum ultrasonic spray pyrolysis deposition technique are made. Optimum device performances are obtained by tuning the layer thickness of TiO2 to 20 nm. High relative permittivity (k) of 53.6 and thin effective oxide thickness of 1.45 nm are also obtained. Pulse-IV, Hooge coefficient (α H), Transmission Electron Microscopy, and atomic force microscope have been performed to characterize the interface, atomic composition, and surface flatness of the TiO2 oxide. Superior improvements for the present TiO2-dielectric MOS-HFET/TiO2-passivated HFETs are obtained, including 47.6%/23.8% in two-terminal gate-drain breakdown voltage (BV GD), 111%/22.2% in two-terminal gate-drain turn-ON voltage (VON), 47.9%/39.4% in ON-state breakdown (BVDS), 12.2%/10.2% in drain-source current density (IDS at VGS) = 0V (IDSS0), 27.2%/11.7% in maximum IDS (IDS, max), 3/1-order enhancement in on/off current ratio (IONIOFF), 58.8%/17.6% in gate-voltage swing linearity, 25.1%/13.2% in unity-gain cutoff frequency (fT), 40.6%/24.7% in maximum oscillation frequency (fmax), and 33.8%/15.6% in power-added efficiency with respect to a Schottky-gated HFET fabricated on the identical epitaxial structure. The present MOS-HFET has also shown stable electrical performances when the ambient temperature is varied from 300 to 450 K. © 1963-2012 IEEE.


Lai Y.-A.,National Cheng Kung University | Chen C.-N.,National Cheng Kung University | Su C.-C.,National Cheng Kung University | Hung S.-H.,National Cheng Kung University | And 4 more authors.
Progress In Electromagnetics Research C | Year: 2011

A compact double-balanced monolithic star mixer for Ka-band applications using 0.25μm GaAs pHEMT process is presented. With multi-coupled lines technology, the proposed dual 180° hybrid is produced and applied to a star mixer successfully. The proposed hybrid adopts the power divider and two types of multi-coupled lines to improve the return loss and isolation at the balance outputs of a traditional dual Marchand balun. Output ports are allowed to locate arbitrarily, eliminating a complex layout while the dual 180° hybrid is applied to double balanced star mixers. As the measurement results show, the proposed mixer achieves an operation bandwidth of 27 to 36 GHz with the best conversion loss of 6.3 dB at 28 GHz. In addition, the chip dimension can be manufactured as small as 0.81 mm2.


Liu H.-Y.,National Cheng Kung University | Lee C.-S.,Feng Chia University | Hsu W.-C.,National Cheng Kung University | Tseng L.-Y.,Feng Chia University | And 3 more authors.
IEEE Transactions on Electron Devices | Year: 2013

Al0.3Ga0.7N AlN}/GaN metal-oxide-semiconductor high electron mobility transistors (HEMTs) grown on Si substrates by using ozone water oxidation method are investigated. Superior improvements of 52.2% in two-terminal gate-drain breakdown voltage (BVGD), 30.3% in drain-source current density (IDS) at VGS=0VIDSS0), 43.6% in maximum IDS(IDS,\max), 34.7% in maximum extrinsic transconductance (gm,\max), and 52.7%/34.3% in unity-gain cutoff/maximum oscillation frequency (fT/fmax) are achieved as compared with a reference Schottky-gated HEMT. Thermal stability is studied by conducting temperature-dependent characterizations of devices at ambient temperatures of 300-550 K. Time-dependent electrical reliability analyses for the devices stressed in off-state (VGS=-20V and VDS=0V) for 0-60 h and on-state (VGS=2 V and VDS=20V) for 0-20 h are also made to physically investigate the dominant degradation mechanisms. Excellent reliability and thermal stability at 300-550 K are achieved by the present design. © 1963-2012 IEEE.


Hu C.-C.,National Cheng Kung University | Lin M.-S.,National Cheng Kung University | Wu T.-Y.,National Cheng Kung University | Adriyanto F.,National Cheng Kung University | And 3 more authors.
ECS Transactions | Year: 2011

Barium-doped TiO 2 films deposited on GaN layers at low temperature through a simple liquid-phase deposition method is investigated. The use as a gate dielectric in AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistors (MOSHEMTs) is also demonstrated. The electrical characteristics of the metal-oxide-semiconductor (MOS) structure on n-doped GaN show that the leakage current density is about 5.09 × 10 -9 A/cm 2 at 1 MV/cm, and the breakdown field is more than 13 MV/cm. The maximum drain current density of the AlGaN/GaN MOSHEMTs is higher than that of HEMTs, in which a wider gate voltage swing, a lower sub-threshold swing (112mV/dec), and a higher I ON/I OFF ratio (4.5 × 10 5) are obtained. ©The Electrochemical Society.


Wu T.-Y.,National Cheng Kung University | Sze P.-W.,Kao Yuan University | Hu C.-C.,National Cheng Kung University | Huang T.-J.,National Cheng Kung University | And 3 more authors.
ECS Transactions | Year: 2011

Through a simple, low-temperature liquid-phase deposition (LPD) method, SrTiO 3 thin films were deposited on GaN as the gate dielectric for metal oxide semiconductor high electron mobility transistor application. X-ray photoelectron spectroscopy was employed to characterize the films. Electrical characteristics of the SrTiO 3 films on GaN showed that the lowest leakage current was 4.2×10 -9 A/cm 2 at -1 MV/cm after annealing at 400°C AlGaN/GaN MOSHEMTs with LPD-SrTiO 3 of 20 nm-thick as the gate dielectric were also fabricated. The suppressed gate leakage current improves both subthreshold slope and on/off current ratio. Wider gate voltage swing and flatter transconductance of the MOSHEMT demonstrate better device linearity. ©The Electrochemical Society.


Hu C.-C.,National Cheng Kung University | Chiu C.-A.,National Cheng Kung University | Yu C.-H.,National Cheng Kung University | Xu J.-X.,National Cheng Kung University | And 4 more authors.
Vacuum | Year: 2015

AlGaN/GaN metal-oxide-semiconductor high electron mobility transistor (MOSHEMT) with a liquid phase deposited (LPD) ZrO2 thin film as gate insulator was fabricated. Compared with the conventional HEMT, the maximum drain current increases from 492 to 627 mA/mm, and leakage current is four orders magnitude lower. The gate swing voltage and off-state breakdown were also improved while applying ZrO2 oxide layer. © 2015 Elsevier Ltd.All rights reserved.


Hu C.-C.,National Cheng Kung University | Lin M.-S.,National Cheng Kung University | Wu T.-Y.,National Cheng Kung University | Adriyanto F.,National Cheng Kung University | And 3 more authors.
IEEE Transactions on Electron Devices | Year: 2012

Barium-doped TiO 2 films deposited on GaN layers at low temperature through a simple liquid phase deposition method is investigated. The use as a gate dielectric in AlGaN/GaN metal-oxide-semiconductor high-electron mobility transistors (MOSHEMTs) is also demonstrated. The electrical characteristics of the MOS structure on n-doped GaN show that the leakage current density is about 5.09 × 10 -9 A/cm 2 at 1 MV/cm, and the breakdown field is more than 13 MV/cm. The maximum drain current density of the AlGaN/GaN MOSHEMTs is higher than that of HEMTs, in which a wider gate voltage swing and a lower subthreshold swing (110 mV/decade) are obtained. The gate leakage current density is significantly improved, and the gate pulse measurement shows that the current collapse is more suppressed for MOSHEMTs. © 2006 IEEE.

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