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Low-Frequency Noise Characterization of AlGaN & x002F;GaN HEMTs and MIS-HEMTs Under UV Illumination
(2020-01-01)
Nagarajan, Venkatesan
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Chen, Kun-Ming
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Lin, Hsin-Yi
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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
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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
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Wu, Chia-Hsun
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Ho, Yu-Hsuan
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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
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Lin, Yueh Chin
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Lin, Min Song
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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 Field Plate on the RF Performance of AlGaN/GaN HEMT Devices
(2012-01-01)
Chiang, Che-Yang
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Hsu, Heng-Tung
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Chang, Edward Yi
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材料科學與工程學系
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Department of Materials Science and Engineering
This paper examines the effect of the field plate structure on the RF performance of AlGaN/GaN High Electron Mobility Transistor (HEMT) devices. While the field plate structure helps to increase the breakdown voltage of the device through modulating the electric field locally, it induces additional feedback capacitance from drain to gate. Such feedback capacitors may impact the overall RF performance of the device especially at high frequencies. Systematic investigations on the small signal as well as power performance as functions of the drain biases are presented. (C) 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of Garry Lee
High Electron Mobility AlGaN/AlN/GaN HEMT Structure With a Nano-scale AlN Interlayer
(2012-01-01)
Huang, Shih-Chun
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Chen, Wen-Ray
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Hsu, Yu-Ting
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Lin, Jia-Ching
;
Chang, Kuo-Jen
Epitaxies of AlGaN/AlN/GaN high electron mobility transistor (HEMT) structures with different thickness of nano-scale AlN interlayers have been realized by metalorganic chemical vapor deposition (MOCVD) technology. After epitaxy, high resolution X-ray diffraction (HRXRD), temperature-dependent Hall Effect and atomic force microscopy (AFM) measurements were used to characterize the properties of these samples. First, it was found that the Al composition of AlGaN layer increases from 21.6 to 34.2% with increasing the thickness of AlN interlayer from 0 to 5 nm under the same AlGaN growth conditions. This result may due to the influences of compressive stress and Al incorporation induced by the AlN interlayer. Then, we also found that the room-temperature (RT) electron mobility stays higher than 1500 cm(2)/Vs in the samples within AlN interlayer thickness range of 1.5 nm, on the other hand, the low-temperature (80K) electron mobility drops dramatically from 8180 to 5720 cm(2)/Vs in the samples with AlN interlayer thickness increasing from 1 to 1.5 nm. Furthermore, it was found that the two-dimensional electron gas (2DEG) density increases from 1.15x10(13) to 1.58x10(13) cm(-2) beyond the AlN interlayer thickness of 1 nm. It was also found that the temperature-independent 2DEG densities are observed in the samples with AlN interlayer thickness of 0.5 and 1 nm. The degenerated characteristics of the samples with AlN thickness thicker than 1.5 nm show the degraded crystalline quality which matched the observation of surface defects and small cracks formations from their AFM images. Finally, the 2DEG mobilities of the proposed structures can be achieved as high as 1705 and 8180 cm(2)/Vs at RT and 80K, respectively.
Effect of AlN Spacer on the AlGaN/GaN HEMT Device Performance at Millimeter-wave Frequencies
(2018-01-01)
Wang, Chun
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Hsu, Heng-Tung
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Huang, Ting-Jui
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Fan, Jun-Kai
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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
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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
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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.

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