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Low-Frequency Noise Characterization of AlGaN & x002F;GaN HEMTs and MIS-HEMTs Under UV Illumination
(2020-01-01)
Nagarajan, Venkatesan
;
Chen, Kun-Ming
;
Lin, Hsin-Yi
;
Hu, Hsin-Hui
;
Huang, Guo-Wei
The low-frequency noise characteristics of AlGaN & x002F;GaN HEMTs and MIS-HEMTs are investigated in the dark condition and under UV illumination. The test devices with a 3-& x03BC;m-thick GaN buffer and a 25-nm-thick Al_0.22Ga_0.78N barrier layer were fabricated on the silicon wafer. For MIS-HEMTs, a 25-nm-thick SiN layer was deposited as a gate dielectric. The measured low-frequency noises show a 1 & x002F;f spectrum and can be described by the carrier number fluctuation model. Different noise responses to the UV light between HEMTs and MIS-HEMTs were observed. By comparing the noise data in dark and under UV illumination, the noise sources under the gate and in the ungated gate-drain access region have been identified. From these results, we can find a design guideline to improve the noise and reliability of GaN-based devices for optoelectronic applications.
Analysis of the back-barrier effect in AlGaN/GaN high electron mobility transistor on free-standing GaN substrates
(2020-01-25)
Liu, Xinke
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Wang, Hao-Yu
;
Chiu, Hsien-Chin
;
Chen, Yuxuan
;
Li, Dabing
The effect of AlGaN back-barrier on AlGaN/GaN high electron mobility transistors (HEMTs) using freestanding GaN wafer has been investigated in this work. With the introducing back-barrier structure, the leakage path underneath the buffer (native nitrogen-vacancies and GaOx compounds of the HVPE-grown free-standing GaN surface) layer can be suppressed by lift-up the conduction band. As compared with AlGaN/GaN HEMTs on SiC wafer, AlGaN/GaN HEMTs on free-standing GaN wafer show enhanced drain current ( 700 mA/mm), improved transconductance (143 mS/mm), less current collapse (12%), higher current gain cut-off frequency (13 GHz), and maximum stable gain cut-off frequency (24 GHz), which is attributed to the higher epi quality layer on free-standing GaN wafer. (C) 2019 Elsevier B.V. All rights reserved.
Recess-Free Normally-off GaN MIS-HEMT Fabricated on Ultra-Thin-Barrier AlGaN/GaN Heterostructure
(2019-01-01)
Han, Ping-Cheng
;
Wu, Chia-Hsun
;
Ho, Yu-Hsuan
;
Yan, Zong-Zheng
;
Chang, Edward Yi
In this work, a recess-free thin AlGaN barrier metal-insulator-semiconductor high electron mobility transistor (MIS-HEMT) with high threshold voltage of 3.19V, high maximum drain current of 716 mA/mm and high breakdown voltage of 906V is demonstrated for the first time. Three different thin barrier structures were compared for device performance. In addition, long-term reliability measurements were carried out to investigate the interface quality of the devices with and without gate recess. The recessfree device exhibits a smaller Vth hysteresis and a more stable performance than those of gate recessed devices. Overall, the recess-free thin barrier AlGaN/GaN MIS-HEMT demonstrates promising performance for power switching applications.
Evaluation of an InAs HEMT with source-connected field plate for high-speed and low-power logic applications
(2019-07-01)
Yao, Jing Neng
;
Lin, Yueh Chin
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Lin, Min Song
;
Huang, Ting Jui
;
Hsu, Heng Tung
In this study, we have presented a source-connected field plate (SCFP) InAs high electron mobility transistor (HEMT) and evaluated its potential for using in high-speed and low-power logic applications. The fabricated device demonstrated good electrical characteristics including low subthreshold swing (SS) of 76 mV/decade, drain induced barrier lowering (DIBL) of 44 mV/V, I-ON/I-OFF ratio of 2.4x10(4), an off-state gate leakage current of less than 5x10(-6) A/mm and a G(m,max) of 1100 mS/mm at V-DS = 0.5 V. When increasing the drain-source bias (V-DS) to 1.0 V, the G(m,max) increased to 1750 mS/mm with a cut-off frequency of 113 GHz. These results revealed that the fabrication of source-connected field plate InAs HEMTs achieved excellent device performance for high-speed and low-power logic applications.
Effect of AlN Spacer on the AlGaN/GaN HEMT Device Performance at Millimeter-wave Frequencies
(2018-01-01)
Wang, Chun
;
Hsu, Heng-Tung
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Huang, Ting-Jui
;
Fan, Jun-Kai
;
Chang, Edward Yi
The effect of the AlN spacer on the performance of AlGaN/GaN HEMT devices at 38 GHz is experimentally investigated. The measurement results revealed that the device with spacer showed superior performance in terms of the maximum drain current. RF wise, substantial improvement in the cut-off frequency and the maximum oscillation frequency was also observed for devices with spacer. A saturated output power density of 4.21 W/mm with 35.02% power-added efficiency (PAE) at 38 GHz were achieved for device with 70nm gate length.
AlGaAs/InGaAs high electron mobility transistor grown on Si substrate with Ge/GexSi1-x metamorphic buffer layers
(2008-09-01)
Chang, Edward Yi
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Huang, Jui-Chien
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Lin, Yueh-Chin
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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.
Novel Metamorphic HEMTs With Highly Doped InGaAs Source/Drain Regions for High Frequency Applications
(2010-10-01)
Sahoo, Kartika Chandra
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Kuo, Chien-I
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Li, Yiming
;
Chang, Edward Yi
;
材料科學與工程學系
In this paper, we report the first result of a strained In(0.52)Ga(0.48) As channel high-electron mobility transistor (HEMT) featuring highly doped In(0.4)Ga(0.6) As source/drain (S/D) regions. A lattice mismatch of 0.9% between In(0.52)Ga(0.48) As and In(0.4)Ga(0.6) As S/D has resulted in a lateral strain in the In(0.52)Ga(0.48) As channel region, where the series resistance is reduced with highly doped S/D regions. An experimentally validated device simulation is advanced for the proposed HEMT, and the results of this paper have shown that there are 60% drive-current and 100% transconductance improvements, compared with the conventional structure. A remarkable 150-GHz increase in the cutoff frequency has been seen for the proposed structure over the conventional one as well for the shown devices.
A versatile low-resistance ohmic contact process with ohmic recess and low-temperature annealing for GaN HEMTs
(2018-09-01)
Lin, Yen-Ku
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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.
High-Performance GaN MOSHEMTs Fabricated With ALD Al2O3 Dielectric and NBE Gate Recess Technology for High Frequency Power Applications
(2017-06-01)
Lin, Yen-Ku
;
Noda, Shuichi
;
Huang, Chia-Ching
;
Lo, Hsiao-Chieh
;
Wu, Chia-Hsun
High-performance GaN metal-oxidesemi-conductor high-electron-mobility transistors (MOSHEMTs) using Al2O3 gate dielectric deposited by atomic layer deposition (ALD) and damage-free neutral beam etch (NBE) gate recess process for millimeter-wave power applications are demonstrated. The high-quality ALD Al2O3 reduces the gate leakage current of the device and the NBE method eliminates the plasma-induced defects in the nitride materials. The MOSHEMT device fabricated exhibits a high maximum drain current density (I-DS,I-max ) of 1.65 A/mm and a high peak extrinsic transconductance (g(m.ext) ) of 653 mS/mm. The MOSHEMT device also demonstrates excellent RF performances, including f(T)/f(MAX) = 183/191 GHz, NFmin = 2.56 dB with G(AS) = 5.61 dB at 54 GHz, and an output power density of 2.7 W/mm associated with a power-added efficiency of 20.9% and a linear power gain of 9.4 dB at 38 GHz. To the best of our knowledge, the noise performance at 54 GHz is the best reported so far for the AlGaN/GaN HEMTs.
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.

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