Browsing by Author "Chang, Edward Yi"

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2H-Silicon Carbide Epitaxial Growth on c-Plane Sapphire Substrate Using an AlN Buffer Layer and Effects of Surface Pre-Treatments
(2015-05-01)
Luong, Tien-Tung
;
Binh Tinh Tran
;
Ho, Yen-Teng
;
Wei, Ting-Wei
;
Wu, Yue-Han
The effects of surface pre-treatments and the role of an AN buffer layer for 2H-SiC growth on c-plane sapphire substrates by thermal CVD are investigated. While the crystallinity of SiC directly grown on sapphire substrate always degrades with a hydrogen pre-treatment but improves by optimizing carbonization, the crystallinity of SiC grown on sapphire substrate using an AN buffer grown by MOCVD improves with sufficient time of exposure to the H pre-treatment but always deteriorates with carbonization. Detailed microstructural analysis by phi-scan x-ray diffraction reveals that SiC film grown on sapphire substrate consists of crystalline domains with two different crystallographic orientations which are rotated relative to each other along the [111] axis by 60 degrees. A highly oriented hexagonal 2H-SiC film is obtained on low-cost c-plane sapphire substrate by using an AN buffer. 2H-SiC is unambiguously determined not only by phi-scan x-ray diffraction but also by high-resolution transmission electron microscopy. The growth relationship between 2H-SiC and 2H-AlN are coherent due to the favorable bonding of C and Al between SiC and AlN.
30 GHz 2-Stage MMIC Low Noise Amplifier using GaAs Pseudomorphic HEMT
(2013)
Rasmi, Amiza
;
Azmi, I. M.
;
Rahim, A. I. A.
;
Hsu, Heng-Tung
;
Chang, Edward Yi
30-GHz Low-Noise Performance of 100-nm-Gate-Recessed n-GaN/AlGaN/GaN HEMTs
(2010-02-01)
Chang, Chia-Ta
;
Hsu, Heng-Tung
;
Chang, Edward Yi
;
Kuo, Chien-I
;
Huang, Jui-Chien
We demonstrate a 100-nm-gate-recessed n-GaN/AlGaN/GaN high-electron mobility transistor (HEMT) with low-noise properties at 30 GHz. The recessed GaN HEMT exhibits a low ohmic-contact resistance of 0.28 Omega . mm and a low gate leakage current of 0.9 mu A/mm when biased at V(GS) = -3 V and V(DS) = 10 V. At the same bias point, a minimum noise figure of 1.6 dB at 30 GHz and an associated gain of 5 dB were achieved. To the best of our knowledge, this is the best noise performance reported at 30 GHz for gate-recessed AlGaN/GaN HEMTs.
460-nm InGaN-Based LEDs Grown on Fully Inclined Hemisphere-Shape-Patterned Sapphire Substrate With Submicrometer Spacing
(2009-10-01)
Chang, Chia-Ta
;
Hsiao, Shih-Kuang
;
Chang, Edward Yi
;
Hsiao, Yu-Lin
;
Huang, Jui-Chien
This letter investigates 460-nm InGaN-based light-emitting diodes (LEDs) grown on a hemisphere-shape-patterned sapphire substrate (HPSS) with submicrometer spacing. The full-width at half-maximum of the (102) plane rocking curves for GaN layer grown on a conventional sapphire substrate (CSS) and HPSS are 480 and 262 arcsec, respectively. Such improvement is due to the reduction of the pure edge threading dislocations. At the forward current of 20 mA, the light output power of the LEDs grown on CSS and HPSS were 4.05 and 5.86 mW, respectively. This improvement of 44% light-output power can be attributed to the improved quality of the material and the increase of the light extraction by the fully inclined facets of the HPSS.
60 GHz broadband Ms-to-CPW hot-via flip chip interconnects
(2007-11-01)
Wu, Wei-Cheng
;
Hsu, Li-Han
;
Chang, Edward Yi
;
Kaernfelt, Camilla
;
Zirath, Herbert
In this letter, the microstrip-to-coplanar waveguide (MS-to-CPW) hot-via flip chip interconnect has been experimentally demonstrated to have broadband performance from dc to 67 GHz. The interconnect structures with the hot-via transitions were first designed and optimized by using the electromagnetic simulation tool. Three types of designs were investigated in this letter. The interconnect structures were then fabricated and radio frequency (RF) tested up to 67 GHz. The optimized interconnect structure with the compensation design demonstrated excellent RF characteristics with the insertion loss less than 0.5 dB and the return loss below 18 dB over a very broad bandwidth from dc to 67 GHz. This is to our knowledge the best result reported for this frequency range.
A 40-nm-Gate InAs/In(0.7)Ga(0.3)As Composite-Channel HEMT with 2200 mS/mm and 500-GHz f(T)
(2009)
Kuo, Chien-I
;
Hsu, Heng-Tung
;
Wu, Chien-Ying
;
Chang, Edward Yi
;
Miyamoto, Yasuyuki
A 40-nm T-gate high-electron-mobility-transistor with InAs/In(0.7)Ga(0.3)As composite-channel has been fabricated. The device exhibits a transconductance (g.) of 2200 mS/mm, a cutoff frequency f(T) of 506 GHz and a minimum noise figure of 1.21 dB at a frequency of 58 GHz. These performances make the device well-suited for millimeter-wave or sub-millimeter-wave applications.
A 60-nm-thick enhancement mode In0.65Ga0.35As/InAs/In0.65Ga0.35As high-electron-mobility transistor fabricated using Au/Pt/Ti non-annealed ohmic technology for low-power logic applications
(2016-02)
Fatah, Faiz Aizad
;
Lin, Yueh-Chin
;
Liu, Ren-Xuan
;
Yang, Kai-Chun
;
Lin, Tai-We
A 60-nm-thick E-mode In0.65Ga0.35As/InAs/In0.65Ga0.35As high-electron-mobility transistor (HEMT) was successfully fabricated and evaluated by using Au/Pt/Ti-based non-annealed ohmic technology for high-speed and low-power logic applications. The device exhibited a minimal SS of 69mV/decade, a lower DIBL of 30mV/V, an ION/IOFF ratio above 1.2 x 10(4) at V-DS = 0.5V and a high f(T) of 378GHz and f(max) of 214GHz at V-DS = 1.0V. These results demonstrate that non-annealed ohmic contacts can be used for fabricating E-mode In0.65Ga0.35As/InAs/In0.65Ga0.35As HEMTs with excellent electrical characteristics. The fabricated HEMTs are likely to find use in future high-speed and low-power logic applications. (C) 2016 The Japan Society of Applied Physics.
A Cu-based alloyed ohmic contact system on n-type GaAs
(2007-12-03)
Chen, Ke-Shian
;
Chang, Edward Yi
;
Lin, Chia-Ching
;
Lee, Cheng-Shih
;
Huang, Wei-Ching
An alloyed Pd/Ge/Cu Ohmic contact to n-type GaAs is reported for the first time. The Pd/Ge/Cu Ohmic contact exhibited a very low specific contact resistance of 5.73x10(-7) Omega cm(2) at a low annealing temperature of 250 degrees C. This result is comparable to the reported Pd/Ge and Au/Ge/Ni Ohmic contact systems to n-type GaAs with doping concentrations about 1x10(18) cm(-3). The Ohmic contact formation mechanisms and microstructure evolution were investigated using secondary ion mass spectrometry, x-ray diffraction, transmission electron microscopy, and energy dispersive spectrometer. The Ohmic contact behavior was related to the formation of Cu(3)Ge and PdGa(x)As(y) compounds after annealing. (c) 2007 American Institute of Physics.
A delta-doped InGaP/InGaAs pHEMT with different doping profiles for device-linearity improvement
(2007-07-01)
Lin, Yueh-Chin
;
Chang, Edward Yi
;
Yamaguchi, Hiroshi
;
Wu, Wei-Cheng
;
Chang, Chun-Yen
In this paper, delta-doped InGaP/InGaAs pseudomorphic high-electron-mobility transistors (pHEMTs) with doping-profile modifications are investigated in order to improve the device linearity. The proposed modification was based on the third-order intermodulation distortion (IM3) and the third-order intercept point (IP3) analysis using a simple equivalent circuit of the devices. The correlations of the extrinsic transconductance (Gm) with IM3 and IP3 indicate that the flatness of Gin, as a function of gate-bias causes a lower IM3 level. On the other hand, a high Gm with a flatter Gm distribution results in higher IP3 value for the device. Therefore, doping modifications that improve the flatness of the Gm distribution will also improve the device linearity. Doping modifications in the Schottky layer (Schottky layer doped) and in the channel layer (channel doped) of the conventional delta-doped InGaP/InGaAs pHEMT were investigated. It was also found that extra doping, either in the channel region or in the Schottky layer, improved the flatness of the Gm distribution under different gate-bias conditions. This achieved a lower IM3 and a higher IP3 with a small sacrifice in the peak Gm value. The power performances of these devices were tested at different drain biases. Even though it had the lowest electron mobility among the three different types of devices studied, the channel-doped device demonstrated the best overall linearity performance, the highest IP3 value, the lowest IM3 level, and the best adjacent-channel power ratio under code-division multiple-access modulation.
A novel AlGaN/GaN multiple aperture vertical high electron mobility transistor with silicon oxide current blocking layer
(2015-08-01)
Shrestha, Niraj Man
;
Wang, Yuen Yee
;
Li, Yiming
;
Chang, Edward Yi
;
材料科學與工程學系
In this work, a new AlGaN/GaN vertical high electron mobility transistor (HEMT) with silicon oxide (SiO2) current blocking layer (CBL) is designed and studied numerically for high-power devices. To overcome the excessive vertical leakage through CBL layer in conventional p-GaN CBL vertical HEMT, large band-gap material, SiO2 is, for the first time, introduced as a CBL material. The band-gap of SiO2 leads to a large barrier which can effectively suppress the vertical leakage even at high drain bias and enhance the breakdown voltage to 1270 V (154% enhancement compared with the conventional p-GaN CBL vertical HEMT). In addition, a device with four parallel apertures is proposed to reduce the aperture resistance, where the total aperture thickness is equal to the aperture thickness of the conventional one. Therefore, the drain current is increased. We not only focus on the vertical leakage control, but also, on the drain current boost (7% improvement). (c) 2014 Elsevier Ltd. All rights reserved.
A Novel Metamorphic High Electron Mobility Transistors with (In(x)Ga(1-x)As)(m)/(InAs)(n) Superlattice Channel Layer for Millimeter-Wave Applications
(2009)
Kuo, Chien-I
;
Hsu, Heng-Tung
;
Lu, Jung-Chi
;
Chang, Edward Yi
;
Wu, Chien-Ying
High performance MHEMTs using (In(x)Ga(1-x)As)(m)/(InAs)(n) superlattice structure as a channel layer have been fabricated successfully. These HEMTs with 80 nm gate length exhibit high drain current density of 392 mA/mm at drain bias 1.0 V and transconductance of 991 mS/mm at drain bias 1.2 V. Comparison with regular In(x)Ga(1-x)As channel, the superlattice channel HEMTs show an outstanding performance because of high electron mobility, and better carrier confinement in the (In(x)Ga(1-x)As)(m)/(InAs)(n) channel layer. The current gain cutoff frequency (f(T)) and maximum oscillation frequency (f(max)) were extracted to be 304 GHz and 162 GHz, respectively. The device demonstrated a 0.75 dB noise figure with an associated gain 9.6 dB at 16 GHz. The excellent device performance shows that the superlattice channel can be practically used for high-frequency and millimeter-wave application.
A simple extraction method for parasitic series resistances in GaN HEMTs considering non-quasi-static effects
(2019-05-01)
Nagarajan, Venkatesan
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Chen, Kun-Ming
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Wang, Huan-Chung
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Singh, Sankalp Kumar
;
Anandan, Deepak
A simple technique for extracting the bias-dependent parasitic series resistances of the GaN-based high electron mobility transistor (HEMT) is demonstrated in this paper. With considering the non-quasi-static effect in devices, new analytical Z-parameter formulations are derived to determine parasitic resistances using the curve-fitting algorithm. More accuracy parasitic resistances can be obtained over a wide fitting frequency range compared to the conventional method which ignores the non-quasi-static effect. Here the intrinsic parameters are then calculated directly from intrinsic Y-parameters after de-embedding the parasitic elements in the small-signal equivalent circuit. An excellent agreement between the measured and simulated S-parameters from 100 MHz to 40 GHz is achieved, which validates the feasibility of our method for extracting the bias-dependent parasitic resistances.
A versatile low-resistance ohmic contact process with ohmic recess and low-temperature annealing for GaN HEMTs
(2018-09-01)
Lin, Yen-Ku
;
Bergsten, Johan
;
Leong, Hector
;
Malmros, Anna
;
Chen, Jr-Tai
Deeply recessed ohmic contacts for GaN-based high electron mobility transistors (HEMTs) are demonstrated. It is shown that low-resistance ohmic contacts can be achieved with recessing beyond the AlGaN Schottky barrier where the ohmic contacts are formed on the sidewall of the recess. This makes the process versatile and relatively insensitive to the exact recess depth. The ohmic contact is based on a gold-free metallization scheme consisting of a Ta/Al/Ta metal stack requiring a low-temperature annealing. Important parameters for this type of ohmic contact process include the metal coverage, slope of the etched sidewall, bottom Ta-layer thickness, as well as annealing temperature and duration. The optimized contact resistance is as low as 0.24 Omega mm after annealing at 575 degrees C. Moreover, this sidewall contact approach was successfully implemented on different epitaxial heterostructures with different AlGaN barrier thickness as well as with and without AlN exclusion layer. All the samples exhibited excellent contact resistances in a wide range of recess depths. The Ta-based, sidewall ohmic contact process is a promising method for forming an ohmic contact on a wide range of GaN HEMT epitaxial designs.
Accurate Performance Evaluation of HEMT Devices for High-Speed Logic Applications through Rigorous Device Modelling Technique
(2007)
Hsu, Heng-Tung
;
Chang, Chia-Yuan
;
Hsu, Heng-Shou
;
Chang, Edward Yi
;
材料科學與工程學系
Tremendous progress has been made recently in the research of novel nanotechnology for future nano-electronic applications. Among all the possible technologies, III-V FETs particularly the heterostructure High Electron Mobility Transistors (HEMT) have demonstrated promising results to be the future device technology for high-speed logic applications. Precise evaluation of the delay performance for HEMT requires highly accurate intrinsic device models extracted from available measurements. In this paper, a rigorous device modelling technique based on 3-D full wave electromagnetic analysis of the device structure is presented. This technique is efficient and accurate, and the determined equivalent circuit model fits the measured S-parameter very well within the frequency range of interest.
[ADJUSTABLE COLLIMATOR AND SPUTTERING APPARATUS WITH THE SAME]
(2005-09-08)
Lee, Cheng-Shih
;
Chang, Edward Yi
An adjustable collimator and a sputtering apparatus with the same are provided. The adjustable collimator comprises an adjustable main body, first and second collimating elements. The adjustable main body has an interior space, a top portion, a bottom portion and an adjuster between the top portion and the bottom portion. The adjuster is adapted for adjusting a relative distance between the top portion and the bottom portion. A first collimating element fixed inside the interior space of the top portion in a manner to move with the top portion and a second collimating element fixed inside the interior space of the bottom portion to move with the bottom portion. When the adjustable collimator applies to sputtering apparatus, it can easily control the incident angel of the molecule of the sputtering material by adjusting a relative distance between the top and bottom portion.
AlGaAs/InGaAs high electron mobility transistor grown on Si substrate with Ge/Ge(x)Si(1-x) metamorphic buffer layers
(2008-09-01)
Chang, Edward Yi
;
Huang, Jui-Chien
;
Lin, Yueh-Chin
;
Hsieh, Yen-Chang
;
Chang, Chia-Yuan
Al(0.12)Ga(0.88)As/In(0.18)Ga(0.82)As high-electron-mobility transistor (HEMT) growth oil a Si substrate using the Ge/Ge(x)Si(1-x) buffer is demonstrated. This is the first demonstration of Al(0.12)Ga(0.88)As/In(0.18)Ga(0.82)As HEMT growth on a Ge/Ge(x)Si(1-x) metamorphic buffer layer. The electron mobility ill tile In(0.18)Ga(0.82)As channel of the HEMT sample was 3.550cm(2)/(Vs). After fabrication. the HEMT device demonstrated a saturation current of 150mA/mm with a transconductance 01 155mS/ inns. The wel behaved characteristics of the HEMT device oil the Si substrate are believed to be due to the very thin buffer layer achieved and the lack of tile antiphase boundary (APB) formation and Ge diffusion into the GaAs layers.
AlGaAs/InGaAs high electron mobility transistor grown on Si substrate with Ge/GexSi1-x metamorphic buffer layers
(2008-09-01)
Chang, Edward Yi
;
Huang, Jui-Chien
;
Lin, Yueh-Chin
;
Hsieh, Yen-Chang
;
Chang, Chia-Yuan
Al0.12Ga0.88As/In0.18Ga0.82As high-electron-mobility transistor (HEMT) growth oil a Si substrate using the Ge/GexSi1-x buffer is demonstrated. This is the first demonstration of Al0.12Ga0.88As/In0.18Ga0.82As HEMT growth on a Ge/GexSi1-x metamorphic buffer layer. The electron mobility ill tile In0.18Ga0.82As channel of the HEMT sample was 3.550cm(2)/(Vs). After fabrication. the HEMT device demonstrated a saturation current of 150mA/mm with a transconductance 01 155mS/ inns. The wel behaved characteristics of the HEMT device oil the Si substrate are believed to be due to the very thin buffer layer achieved and the lack of tile antiphase boundary (APB) formation and Ge diffusion into the GaAs layers.
AlGaN/GaN HEMTs With Damage-Free Neutral Beam Etched Gate Recess for High-Performance Millimeter-Wave Applications
(2016-11)
Lin, Yen-Ku
;
Noda, Shuichi
;
Lo, Hsiao-Chieh
;
Liu, Shih-Chien
;
Wu, Chia-Hsun
The electrical performances of gate-recessed AlGaN/GaN high-electron mobility transistors (HEMTs) fabricated using the damage-free neutral beam etching (NBE) method are demonstrated. The NBE method could eliminate the plasma-induced defects generated by irradiating ultraviolet/VUV photons in the conventional inductively coupled plasma reactive ion etching method. The AlGaN/GaN HEMT device fabricated using the new gate recess process exhibited superior electrical performances, including a maximum drain current density (I-DS,I-max) of 1.54 A/mm, low 1/f noise, a current-gain cutoff frequency (f(T)) of 153 GHz, a maximum frequency of oscillation (f(MAX)) of 167 GHz, and a minimum noise figure (NFmin) of 3.28 dB with an associated gain (G(AS)) of 5.06 dB at 54 GHz. Such superior characteristics confirm the inherent advantages of adopting the damage-free NBE process in fabricating GaN devices for millimeter-wave applications.
AlGaN/GaN HEMTs With Damage-Free Neutral Beam Etched Gate Recess for High-Performance Millimeter-Wave Applications (vol 37, pg 1395, 2016)
(2017-01)
Lin, Yen-Ku
;
Noda, Shuichi
;
Lo, Hsiao-Chieh
;
Liu, Shih-Chien
;
Wu, Chia-Hsun
AlGaN/GaN HEMTs With Damage-Free Neutral Beam Etched Gate Recess for High-Performance Millimeter-Wave Applications (vol 37, pg 1395, 2016)
(2017-01)
Lin, Yen-Ku
;
Noda, Shuichi
;
Lo, Hsiao-Chieh
;
Liu, Shih-Chien
;
Wu, Chia-Hsun