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High Performance Normally-Off AlGaN/GaN MIS-HEMT Using Charge Storage Technique
(2019-01-01)
Han, Ping-Cheng
;
Yang, Chih-Yi
;
Lee, Ming-Wen
;
Wu, Jui-Sheng
;
Wu, Chia-Hsun
High-Performance In0.53Ga0.47As FinFETs for logic and RF Applications
(2019-01-01)
Chang, Edward Yi
;
Luc, Ho Quang
;
Lin, Chin Yueh
;
交大名義發表
;
National Chiao Tung University
Study of Charge Trapping Effects on AlGaN/GaN HEMTs Under UV Illumination With Pulsed I-V Measurement
(2020-06-01)
Nagarajan, Venkatesan
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Chen, Kun-Ming
;
Chen, Bo-Yuan
;
Huang, Guo-Wei
;
Chuang, Chia-Wei
The charge trapping effects on AlGaN/GaN HEMTs under UV illumination are investigated using the pulsed current-voltage (I-V) measurement method. The test samples are unpassivated Schottky-gate HEMTs and metal-insulator-semiconductor HEMTs (MIS-HEMTs) with SiN gate dielectric. For HEMTs, the dominant charge trapping sources are the surface trap states, whereas, for MIS-HEMTs, they are trap states in the SiN gate dielectric and GaN buffer. When these devices are shined with the UV light, the drain current increases apparently in both samples owing to the generated photocurrent. By combining the UV illumination and pulsed I-V measurement, we find out the UV light has less effect on the surface charge trapping in the unpassivated HEMTs. Moreover, in MIS-HEMTs, we observe the charge trapping in the SiN gate dielectric becomes more serious under UV illumination, whereas the charge trapping in the GaN buffer is suppressed significantly. These findings are important for designing a GaN-based HEMT for photonic applications. In addition, the different responses of the surface-, buffer-, and gate-dielectric-related charge trapping to the UV light suggest that it would be easier to distinguish the trap types by introducing the UV illumination during the pulse measurement.
High performance UV photodetector based on MoS2 layers grown by pulsed laser deposition technique
(2020-09-15)
Kumar, Sujit
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Sharma, Anjali
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Ho, Yen Teng
;
Pandey, Akhilesh
;
Tomar, Monika
Highly efficient ultraviolet (UV) photodetector based on Molybdenum Disulfide (MoS2) layers has been fabricated using pulsed laser deposition (PLD) technique. Systematic layer dependent photoresponse studies have been performed from single layer to 10 layers of MoS2 by varying the laser pulses to see the effect of the number of layers on the photoelectrical measurements. Raman and Photoluminescence studies have been carried out to ensure the growth of high-quality MoS2 layers. Layers of MoS2 grown at 100 pulses were found to exhibit the characteristic Raman phonon modes i.e. E-2g(1) and A(1g )at 383.8 cm(-1) and 405.1 cm(-1) respectively and Photoluminescence (PL) spectra show B exciton peak for MoS2 at around 625 nm suggesting the growth of high-quality MoS2 layers. Atomic force microscopy (AFM) thickness profiling and cross sectional-high resolution transmission electron microscopy (HRTEM) analysis gives the thickness of grown MoS2 to be 2.074 nm and 1.94 nm, respectively, confirming the growth of trilayers of MoS2. X-ray photoelectron spectroscopy (XPS) spectra of the grown trilayer sample show characteristic peaks corresponding to Molybdenum and Sulphur doublet (Mo4+ 3d(5/2,3/2) and S 2p(3/2,1/2)) confirming the chemical state of pure MoS2 phase without the presence of any Molybdenum oxide state. Dynamic photoelectrical studies with Indium Tin Oxide (ITO) as contact electrode upon UV laser illumination show superior responsivity of 3 x 10(4) A/W at 24 mu W optical power of the incident laser (lambda = 365 nm) and very high detectivity of 1.81 x 10(14) Jones at a low applied bias of 2 V. The obtained results are highly encouraging for the realization of low power consumption and highly efficient UV photodetectors based on MoS2 layers. (C) 2020 Elsevier B.V. All rights reserved.
Reliability Characterization of Gallium Nitride MIS-HEMT Based Cascode Devices for Power Electronic Applications
(2020-05-01)
Elangovan, Surya
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Cheng, Stone
;
Chang, Edward Yi
;
機械工程學系
;
材料科學與工程學系
We present a detailed study of dynamic switching instability and static reliability of a Gallium Nitride (GaN) Metal-Insulator-Semiconductor High-Electron-Mobility-Transistor (MIS-HEMT) based cascode switch under off-state (negative bias) Gate bias stress (V-GS,V- OFF). We have investigated drain channel current (I-DS,I- Max) collapse/degradation and turn-on and rise-time (t(R)) delay, on-state resistance (RDS-ON) and maximum transconductance (G(m, max)) degradation and threshold voltage (V-TH) shift for pulsed and prolonged off-state gate bias stress V-GS,V- OFF. We have found that as stress voltage magnitude and stress duration increases, similarly I-DS,I- Max and RDS-ON degradation, V-TH shift and turn-on/rise time (t(R)) delay, and G(m, max) degradation increases. In a pulsed off-state V-GS,V- OFF stress experiment, the device instabilities and degradation with electron trapping effects are studied through two regimes of stress voltages. Under low stress, V-TH shift, I-DS collapse, RDS-ON degradation has very minimal changes, which is a result of a recoverable surface state trapping effect. For high-stress voltages, there is an increased and permanent V-TH shift and high I-DS,I- Max and RDS-ON degradation in pulsed V-GS,V- Stress and increased rise-time and turn-on delay. In addition to this, a positive V-TH shift and G(m, max) degradation were observed in prolonged stress experiments for selected high-stress voltages, which is consistent with interface state generation. These findings provide a path to understand the failure mechanisms under room temperature and also to accelerate the developments of emerging GaN cascode technologies.
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.
Enhancement of electron transport properties of InAlGaN/AlN/GaN HEMTs on silicon substrate with GaN insertion layer
(2020-06-01)
Kao, Min-Lu
;
Ha, Minh Thien Huu
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Lin, Yuan
;
Weng, You-Chen
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Hsu, Heng-Tung
InAlGaN/AlN/GaN high electron mobility transistors (HEMTs) on a silicon substrate with high electron mobility is demonstrated for the first time. The InAlGaN/AlN/GaN heterostructures has a high electron mobility of 1540 cm(2) V-1 s(-1) and low sheet resistance of 228.2 omega sq(-1) by inserting a thin GaN interlayer (IL) between InAlGaN and AlN layers. The experimental results demonstrate that an optimized GaN IL contributes to a better atomic arrangement of the InAlGaN barrier layer in the InAlGaN/GaN HEMTs and results in better electron transport properties for the device. The InAlGaN/GaN device with 170 nm gate and 2 mu m source-to-drain distance shows a high maximum current density (I-max) of 1490 mA mm(-1) and high transconductance (g(m)) of 401 mS mm(-1). Such results demonstrate the potential of adopting InAlGaN/GaN heterostructure on silicon for low cost mm-wave applications in the future.
Study of E-Mode AlGaN/GaN MIS-HEMT with La-silicate Gate Insulator for Power Applications
(2020-02-01)
Huang, Kuan Ning
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Lin, Yueh-Chin
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Lin, Jia-Ching
;
Hsu, Chia Chieh
;
Lee, Jin Hwa
An enhancement-mode (E-mode) AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT) with La2O3/SiO2 gate insulator is investigated for high power application. The La2O3/SiO2 composite oxide formed amorphous La-silicate after post deposition annealing. Good oxide film quality and excellent La-silicate/AlGaN interface properties were achieved as evidenced by the capacitance-voltage (C-V) curves and hysteresis effect of the La-silicate on AlGaN/GaN metal-oxide-semiconductor capacitors. As a result, the E-mode AlGaN/GaN MIS-HEMT with La-silicate gate insulator shows good threshold voltage (V-th) stability and demonstrated only slightly increase in the dynamic on-resistance (R-on) after high drain bias stress test. The device also exhibits high current density of 752 mA/mm, high maximum transconductance of 210 mS/mm, low subthreshold swing of 104 mV/decade, and I-ON/I-OFF = 10(7) when tested at V-DS = 10 V. Furthermore, low on-resistance of 7.6 omega mm, high breakdown voltage of 670 V, and excellent delay time of 4.2 ps were achieved, demonstrating the La-silicate MIS-HEMTs have the potential to be used for power electronic applications.
Ohmic Contacts with low contact resistance for GaN HEMTs
(2019-01-01)
Chang, Edward Yi
;
Lin, Yen-Ku
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材料科學與工程學系
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電子工程學系及電子研究所
;
國際半導體學院
GaN-based high electron mobility transistor (HEMT) is a promising candidate for high-frequency and high-power applications due to its outstanding material properties, such as high electric breakdown field and high peak electron drift velocity. A low contact resistance (R-c) contact is essential for the device performance including output power, power efficiency, frequency response and noise performances. To obtain low contact resistances, several studies using different metallization schemes have been demonstrated. A standard Ti/Al/Ni/Au metal stack is a conventional ohmic contact of GaN HEMTs. Ti reacts with AlGaN to form TiN, which results in the creation of nitrogen vacancies which act as donors in AlGaN layers. The resultant N-type doped AlGaN and the conductive TiN facilitate tunneling mechanism of carriers at the interface.
Low resistive InGaN film grown by metalorganic chemical vapor deposition
(2020-01-01)
Shrestha, Niraj Man
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Chauhan, Prerna
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Wong, Yuen-Yee
;
Li, Yiming
;
Samukawa, Seiji
Indium gallium nitride (InGaN) samples were grown on sapphire substrate with low temperature GaN buffer by metalorganic chemical vapor deposition (MOCVD) under varying growth conditions, such as temperature, pressure and ammonia flow. Although high indium composition is considered as indispensable parameter for sheet carrier concentration (n(s)) and low sheet resistance (R-s), our outcomes disclose that higher indium composition in InGaN film doesn't always have high n(s) and low R-s. Acceptor nature of carbon related defects, a major trapping sites for electrons, plays a crucial role to limit the carrier concentrations in the InGaN specially grown at low pressure, low temperature and low ammonia flow. Furthermore, study of metal contacts deposited on the grown samples by transmission line method (TLM) shows that carrier concentration is the most important factor to obtain low contact resistance. The measured contact resistance for the sample with 4.5x 10(16) cm(2) carrier concentration is 0.13 Omm which is among the lowest contact resistance for GaN based materials grown by MOCVD. This proves that the use of InGaN in source and drain contact region can surpassingly reduce contact resistance and significantly improve device performance of AlGaN/GaN device.

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