Browsing by Author "Wong, Yuen-Yee"

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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
Characterization of AlInN Layer Grown on GaN/Sapphire Substrate by MOCVD
(2013-02-01)
Huang, Wei-Ching
;
Chang, Edward-Yi
;
Wong, Yuen-Yee
;
Lin, Kung-Liang
;
Hsiao, Yu-Lin
The AlInN layers have been grown with different growth parameters on GaN/sapphire substrates by metal-organic chemical vapor deposition (MOCVD). The effects of growth parameters such as pressure and temperature on the Al incorporation during AlInN material growth have been investigated. The results showed that lower pressure provides a tendency for higher Al incorporating in the AlInN layer. Besides, as the temperature was increased from 700 degrees C to 780 degrees C, an estimation of 4% reduction on the indium composition has been observed for each 20 degrees C increment. XRD analysis showed that the best crystal quality of AlInN occured at 80% Al composition because of the higher lattice matching with GaN. Based on the above criteria, an Al0.8In0.2N/GaN HEMT device with 2 mu m gate length has also been fabricated. The DC characteristics showed a saturated current, I-dss of 280 mA/mm and transconductance of 140 mS/mm.
Demonstrating 1 nm-oxide-equivalent-thickness La2O3 and HfO2 multi-layer composite oxides on In0.53Ga0.47As MOS capacitor
(2016-01-08)
Wu, Wen-Hao
;
Lin, Yueh-Chin
;
Hou, Tzu-Ching
;
Lin, Tai-Wei
;
Hsu, Hisang-Hua
The use of a high k composite dielectric composed of La2O3 and HfO2 layers as the gate dielectric for In0.53Ga0.47As MOS application is proposed. Two multi-layer structures of La2O3 (1 nm)/HfO2 (1 nm) and La2O3 (0.5 nm)/HfO2 (0.5 nm) were deposited and annealed at 450 and 500 degrees C for device performance comparison. X-ray photoelectron spectroscopy, TEM and C-V measurements were used for the interface analysis between the oxide and the semiconductor. Finally, a 1 nm equivalent-oxide-thickness dielectric with small hysteresis of 88 mV and D-it of 1.9 x 10(12) cm(-2) eV(-1) was achieved for six layers of an La2O3 (0.5 nm)/HfO2 (0.5 nm) composite oxide structure on an In0.53Ga0.47As MOS capacitor with a post-deposition annealing temperature of 450 degrees C.
Dependence of GaN Defect Structure on the Growth Temperature of the AlN Buffer Layer
(2008)
Wong, Yuen-Yee
;
Chang, Edward Yi
;
Yang, Tsung-Hsi
;
Chang, Jet-Rung
;
Chen, Yi-Cheng
The defect structure of the GaN film grown on sapphire by plasma-assisted molecular beam epitaxy (PAMBE) technique was found to be dependent on the AlN buffer layer growth temperature. This buffer growth temperature controlled the defect density in GaN film but had shown contrary effects on the density of screw threading dislocation (TD) and edge TD. The density of screw TD was high on lower temperature buffer but low on the higher temperature buffer. Meanwhile the density of edge TD had shown the opposite. Further examinations have suggested that the defect structure was closely related to the stress in the GaN film, which can be controlled by the growth temperature of the AlN buffer. Using the 525 degrees C AlN buffer, optimum quality GaN Film with relatively low screw and edge TDs were achieved.
Direct growth of a 40 nm InAs thin film on a GaAs/Ge heterostructure by metalorganic chemical vapor deposition
(2014-09-01)
Yu, Hung-Wei
;
Wang, Tsun-Ming
;
Nguyen, Hong-Quan
;
Wong, Yuen-Yee
;
Tu, Yung-Yi
In this paper, the authors directly grew an InAs thin film (40 nm) by metalorganic chemical vapor deposition on GaAs/Ge substrates by using flow-rate modulation epitaxy with an appropriate V/III ratio. The growth of a high-quality InAs thin film with periodic 90 degrees misfit dislocations was related to a uniform monolayer In atom distribution at the InAs/GaAs interface. The In monolayer effectively minimized the difference between surface energy and strain energy, producing a stable interface during material growth. The authors also found that a tightly controlled V/III ratio can improve the quality of the InAs islands on the GaAs/Ge heterostructures, though it is not the key factor in InAs thin-film growth. (C) 2014 American Vacuum Society.
Dislocation reduction in GaN film using Ga-lean GaN buffer layer and migration enhanced epitaxy
(2011-07-29)
Wong, Yuen-Yee
;
Chang, Edward Yi
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Wu, Yue-Han
;
Hudait, Mantu K.
;
Yang, Tsung-Hsi
A GaN buffer layer grown under Ga-lean conditions by plasma-assisted molecular beam epitaxy (PAMBE) was used to reduce the dislocation density in a GaN film grown on a sapphire substrate. The Ga-lean buffer, with inclined trench walls on its surface, provided an effective way to bend the propagation direction of dislocations, and it reduced the dislocation density through recombination and annihilation processes. As a result, the edge dislocation density in the GaN film was reduced by approximately two orders of magnitude to 2 x 10(8) cm(-2). The rough surface of the Ga-lean buffer was recovered using migration enhanced epitaxy (MEE), a process of alternating deposition cycle of Ga atoms and N(2) radicals, during the PAMBE growth. By combining these two methods, a GaN film with high-crystalline-quality and atomically-flat surface can be achieved by PAMBE on a lattice mismatch substrate. (C) 2011 Elsevier B.V. All rights reserved.
Effect of Nitridation on the Regrowth Interface of AlGaN/GaN Structures Grown by Molecular Beam Epitaxy on GaN Templates
(2012-08-01)
Wong, Yuen-Yee
;
Huang, Wei-Ching
;
Trinh, Hai-Dang
;
Yang, Tsung-Hsi
;
Chang, Jet-Rung
AlGaN/GaN structures were regrown on GaN templates using plasma- assisted molecular beam epitaxy (PA-MBE). Prior to the regrowth, nitridation was performed using nitrogen plasma in the MBE chamber for different durations (0 min to 30 min). Direct-current measurements on high-electron-mobility transistor devices showed that good pinch-off characteristics and good interdevice isolation were achieved for samples prepared with a 30-min nitridation process. Current-voltage measurements on Schottky barrier diodes also revealed that, for samples prepared without nitridation, the reverse-bias gate leakage current was approximately two orders of magnitudes larger than that of samples prepared with a 30-min nitridation process. The improvement in the electrical properties is a result of contaminant removal at the regrowth interface which may be induced by the etching effect of nitridation.
Effect of Postdeposition Annealing Temperatures on Electrical Characteristics of Molecular-Beam-Deposited HfO2 on n-InAs/InGaAs Metal-Oxide-Semiconductor Capacitors
(2012-02-01)
Trinh, Hai-Dang
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Lin, Yueh-Chin
;
Wang, Huan-Chung
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Chang, Chia-Hua
;
Kakushima, Kuniyuki
The electrical characteristics of molecular-beam-deposited HfO2/n-InAs/InGaAs metal-oxide-semiconductor capacitors with different postdeposition annealing (PDA) temperatures (400-550 degrees C) are investigated. Results show that the sample with the PDA temperature of 500 degrees C exhibits the best capacitance-voltage (C-V) behavior with small frequency dispersion and small hysteresis. The X-ray photoelectron spectroscopy (XPS) spectra show the reduction of the amount of As-related oxides to below the XPS detection level when the PDA temperature is up to 500 degrees C. As the PDA temperature was increased to above 500 degrees C, As and In atoms seem to diffuse significantly into HfO2, resulting in the degradation of C-V behavior. (C) 2012 The Japan Society of Applied Physics
Effects of Al(x)Ga(1-x)N interlayer for GaN epilayer grown on Si substrate by metal-organic chemical-vapor deposition
(2010-05-01)
Lin, Kung-Liang
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Chang, Edward-Yi
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Hsiao, Yu-Lin
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Huang, Wei-Ching
;
Luong, Tien-Tung
GaN film grown on Si substrate using multilayer AlN/Al(x)Ga(1-x)N buffer is studied by the low-pressure metal-organic chemical-vapor deposition method. The Al(x)Ga(1-x)N films with Al composition varying from 1 to 0.66 were used to accommodate the stress induced between GaN and the Si substrate during GaN growth. The correlation of the Al composition in the Al(x)Ga(1-x)N films with respect to the stress induced in the GaN film grown was studied using high-resolution x-ray diffraction, including symmetrical and asymmetrical omega/2 theta scans and reciprocal space maps. It is found that with proper design of the Al composition in the Al(x)Ga(1-x)N buffer layer, crack-free GaN film can be successfully grown on 6 in. Si (111) substrates using multilayer AlN and Al(x)Ga(1-x)N buffer layers. (C) 2010 American Vacuum Society. [DOI: 10.1116/1.3385672]
Effects of initial GaN growth mode on the material and electrical properties of AlGaN/GaN high-electron-mobility transistors
(2014-09-01)
Wong, Yuen-Yee
;
Chang, Edward Yi
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Huang, Wei-Ching
;
Lin, Yueh-Chin
;
Tu, Yung-Yi
AlGaN/GaN high-electron-mobility transistors (HEMTs) with different initial GaN growth modes were prepared on AIN/sapphire substrates. Secondary ion mass spectroscopy and Hall effect measurements confirmed that a highly conductive n-type region was generated at the GaN/AIN buffer interface during the three-dimensional to two-dimensional (3D-2D) growth mode transition. This n-type region was created by oxygen impurity incorporation during the 3D-2D growth mode transition, and its thickness increased with the transition time. The existence of this n-type conduction path not only changed the material properties but also degraded the device performance of HEMTs. (C) 2014 The Japan Society of Applied Physics
Effects of NH3 Flow Rate During AlGaN Barrier Layer Growth on the Material Properties of AlGaN/GaN HEMT Heterostructure
(2017-10-01)
Lumbantoruan, Franky J.
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Wong, Yuen-Yee
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Huang, Wei-Ching
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Yu, Hung-Wei
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Chang, Edward-Yi
NH3 flow rate during AlGaN barrier layer growth not only affects the growth efficiency and surface morphology as a result of parasitic reactions but also influences the concentration of carbon impurity in the AlGaN barrier. Carbon, which decomposes from metal precursors, plays a role in electron compensation for AlGaN/GaN HEMT. No 2-dimensional electron gas (2-DEG) was detected in the AlGaN/GaN structure if grown with 0.5 slm of NH3 due to the presence of higher carbon impurity (2.6 x 10(19) cm(-2)). When the NH3 flow rate increased to 6.0 slm, the carbon impurity reduced to 2.10 x 10(18) atom cm(-3) and the 2 DEG electron density recovered to 9.57 x 10(12) cm(-2).
Effects of Wet Chemical and Trimethyl Aluminum Treatments on the Interface Properties in Atomic Layer Deposition of Al(2)O(3) on InAs
(2010-11-01)
Trinh, Hai-Dang
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Chang, Edward Yi
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Wong, Yuen-Yee
;
Yu, Chih-Chieh
;
Chang, Chia-Yuan
The reduction of native oxides on an In As surface using various wet and dry chemical treatments including hydrochloric acid (HCl) treatment sulfide treatment and in situ trimethyl aluminum (TMA) treatment before the atomic layer deposition (ALD) of Al(2)O(3) on In As is studied X ray photoelectron spectrum (XPS) results show that the effect of surface cleaning by TMA was apparent almost after the first pulse but that TMA cleaning is not as effective as wet chemical surface cleaning The combination of wet chemical treatment and TMA pretreatment is the most effective method for In As surface cleaning as indicated by the XPS analysis Capacitance-voltage (C-V) and current density-voltage (J-V) characteristics on metal-oxide-semiconductor capacitance (MOSCAP) structures were also investigated to evaluate the Al(2)O(3)/n In As interface quality after different surface treatments and the results are consistent with the XPS analysis (C) 2010 The Japan Society of Applied Physics
Effects of Wet Chemical and Trimethyl Aluminum Treatments on the Interface Properties in Atomic Layer Deposition of Al2O3 on InAs
(2010-11-01)
Trinh, Hai-Dang
;
Chang, Edward Yi
;
Wong, Yuen-Yee
;
Yu, Chih-Chieh
;
Chang, Chia-Yuan
The reduction of native oxides on an In As surface using various wet and dry chemical treatments including hydrochloric acid (HCl) treatment sulfide treatment and in situ trimethyl aluminum (TMA) treatment before the atomic layer deposition (ALD) of Al2O3 on In As is studied X ray photoelectron spectrum (XPS) results show that the effect of surface cleaning by TMA was apparent almost after the first pulse but that TMA cleaning is not as effective as wet chemical surface cleaning The combination of wet chemical treatment and TMA pretreatment is the most effective method for In As surface cleaning as indicated by the XPS analysis Capacitance-voltage (C-V) and current density-voltage (J-V) characteristics on metal-oxide-semiconductor capacitance (MOSCAP) structures were also investigated to evaluate the Al2O3/n In As interface quality after different surface treatments and the results are consistent with the XPS analysis (C) 2010 The Japan Society of Applied Physics
Epitaxial Overgrowth of Gallium Nitride Nano-Rods on Silicon (111) Substrates by RF-Plasma-Assisted Molecular Beam Epitaxy
(2010)
Ku, Jui-Tai
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Yang, Tsung-Hsi
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Chang, Jet-Rung
;
Wong, Yuen-Yee
;
Chou, Wu-Ching
Strain-free gallium nitride (GaN) overgrowth on GaN nano-rods is realized by RF-plasma assisted molecular beam epitaxy (RF-MBE) on silicon (Si) substrate. The strain-free condition was identified by the strong free A exciton (FX(A)) photoluminescence (PL) peak at 3.478 eV and the E(2) high phonon Raman shift of 567 cm(-1). It is clearly demonstrated that the critical diameter of GaN nano-rods is around 80nm for the overgrowth of strain-free GaN. The blue-shift of PL peak energy and phonon Raman energy with decreasing the diameter of nano-rod result from the strain relaxation of overgrowth GaN. (C) 2010 The Japan Society of Applied Physics
Growth and Fabrication of AlGaN/GaN HEMT on SiC Substrate
(2012-01-01)
Wong, Yuen-Yee
;
Chiu, Yu-Sheng
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Luong, Tien-Tung
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Lin, Tai-Ming
;
Ho, Yen-Teng
AlGaN/GaN high electron mobility transistor (HEMT) was grown on silicon carbide substrate by metalorganic chemical vapor deposition technique. The AlGaN/GaN structure was optimized by tuning the growth conditions such as AlN buffer thickness, and the Al composition and thickness of AlGaN barrier layer. As a result, the X-ray rocking curve widths were 277 arcsec and 324 arcsec for the GaN (002) and (102) planes, respectively, indicating a high crystalline quality. Hall measurement showed that the AlGaN/GaN structure has a high electron mobility of 1840 (cm(2)/V-s) and a sheet electron concentration of 9.85 x10(12) cm-(2). Besides, HEMT device with sub-micron gate-length (0.7 mu m) was also successfully fabricated. DC measurement showed that the HEMT device has a saturated current of 800 mA/mm, a transconductance of 257 mS/mm and an off-state breakdown voltage larger than 100 V. For RF performance, the device has achieved an output power density (P-out), gain, and power added efficiency (PAE) of 7 W/mm, 23.5 dB and 61.7%, respectively, measured at 2 GHz frequency. On the other hand, the RF performance measured at 8 GHz showed that the device could achieve P-out, gain and PAE of 5.01 W/mm, 14.9 dB and 26.23% respectively.
Growth of High-Quality In(0.4)Ga(0.6)N Film on Si Substrate by Metal Organic Chemical Vapor Deposition
(2011-11-01)
Binh-Tinh Tran
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Chang, Edward-Yi
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Lin, Kung-Liang
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Wong, Yuen-Yee
;
Sahoo, Kartika Chandra
High-quality In(0.4)Ga(0.6)N film grown on GaN/AlN/Si(111) templates was obtained by metal organic chemical vapor deposition (MOCVD) with negligible phase separation. A template of high-quality GaN grown on a Si(111) substrate using AlN buffer layers was used for subsequent In(0.4)Ga(0.6)N growth. The GaN layer was 0.6 mu m thick with rocking-curve full width at half maximum (FWHM) for a GaN(002) peak better than 430 arcsec. The In(0.4)Ga(0.6)N film grown was 0.3 mu m thick with a dislocation density of 6 x 10(7) cm(-2) and X-ray (omega-2 theta) FWHM better than 130 arcsec. (C) 2011 The Japan Society of Applied Physics
Growth of High-Quality In0.4Ga0.6N Film on Si Substrate by Metal Organic Chemical Vapor Deposition
(2011-11-01)
Binh-Tinh Tran
;
Chang, Edward-Yi
;
Lin, Kung-Liang
;
Wong, Yuen-Yee
;
Sahoo, Kartika Chandra
High-quality In0.4Ga0.6N film grown on GaN/AlN/Si(111) templates was obtained by metal organic chemical vapor deposition (MOCVD) with negligible phase separation. A template of high-quality GaN grown on a Si(111) substrate using AlN buffer layers was used for subsequent In0.4Ga0.6N growth. The GaN layer was 0.6 mu m thick with rocking-curve full width at half maximum (FWHM) for a GaN(002) peak better than 430 arcsec. The In0.4Ga0.6N film grown was 0.3 mu m thick with a dislocation density of 6 x 10(7) cm(-2) and X-ray (omega-2 theta) FWHM better than 130 arcsec. (C) 2011 The Japan Society of Applied Physics
Impact of Q-Time on the Passivation of Al2O3/p-In0.53Ga0.47As Interfaces Using Various Surface Treatments
(2014)
Luc, Quang-Ho
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Chang, Edward Yi
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Trinh, Hai-Dang
;
Wong, Yuen-Yee
;
Do, Huy-Binh
In this article, we demonstrate the influences of atmosphere exposure duration between extrinsic chemical treatment and ALD chamber loading (Q-time) on the passivation effect of the Al2O3/p-In0.53Ga0.47As interfaces. With the use of various chemical solutions and TMA pretreatment, nice capacitance-voltage (C-V) characteristics of Al2O3/p-In0.53Ga0.47As metal-oxide-semiconductor capacitors (MOSCAPs) were obtained with different Q-times before the ALD-Al2O3 deposition. This confirms that Q-time is not the critical issue determining the Al2O3/In0.53Ga0.47As interface quality. X-ray photoelectron spectroscopy (XPS) analyzes in conjunction with the electrical characterizations have implied that the InGaAs native oxides might not play a major role on the interface trap states formation. (C) 2014 The Electrochemical Society. All rights reserved.