High Electron Mobility Transistors With Al<sub>0.65</sub>Ga<sub>0.35</sub>N Channel Layers on Thick AlN/Sapphire Templates

Muhtadi, Sakib; Hwang, Seong Mo; Coleman, Antwon; Asif, Fatima; Simin, Grigory; Chandrashekhar, M. V. S.; Khan, Asif

doi:10.1109/led.2017.2701651

Cited by 53 publications

(31 citation statements)

References 18 publications

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“…31 It is especially favored at high x because of its high critical electric field, estimated at E C ≥ 1.1 × 10 7 V/cm for Al 0.70 Ga 0.30 N. Table I provides a compilation of Al x Ga 1-x N-channel HEMTs with x ≥ 0.5 using various approaches to ohmic contacts for comparison to the present work. Notably, Muhtadi et al used a Zr/Al/Mo/Au planar metal stack with x = 0.65 which resulted in a current density of 250 mA/mm at a threshold voltage of approximately −10 V and an offset voltage approaching 5 V. 9 No contact resistivity numbers were provided, although they are estimated at approximately 60 -mm for V DS >5 V from the data in the paper. Tokuda et al and Yafune et al utilized Zr/Al/Mo/Au metal stacks while Ti/Al based metals were deemed unsatisfactory.…”

Section: Resultsmentioning

confidence: 99%

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Al_0.85Ga_0.15N/Al_0.70Ga_0.30N High Electron Mobility Transistors with Schottky Gates and Large On/Off Current Ratio over Temperature

Baca

Klein

Allerman

et al. 2017

ECS J. Solid State Sci. Technol.

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AlGaN-channel high electron mobility transistors (HEMTs) are among a class of ultra wide-bandgap transistors that are promising candidates for RF and power applications. Long-channel Al x Ga 1-x N HEMTs with x = 0.7 in the channel have been built and evaluated across the −50 • C to +200 • C temperature range. These devices achieved room temperature drain current as high as 46 mA/mm and were absent of gate leakage until the gate diode forward bias turn-on at ∼2.8 V, with a modest −2.2 V threshold voltage. A very large I on /I off current ratio, of 8 × 10 9 was demonstrated. A near ideal subthreshold slope that is just 35% higher than the theoretical limit across the temperature range was characterized. The ohmic contact characteristics were rectifying from −50 • C to +50 • C and became nearly linear at temperatures above 100 • C. An activation energy of 0.55 eV dictates the temperature dependence of off-state leakage. AlGaN-channel high electron mobility transistors (HEMTs) are among a class of ultra wide-bandgap transistors (UWBG) that are promising candidates for power and RF applications.1-9 Their promise derives from the large critical electric field, which scales as a power law with the bandgap of the material, 10 e.g. E C ∼ E G 2.5 (the exact dependence is a topic of active research) and provides favorable power and RF figures of merit. Enhancement-mode HEMTs are required for power applications, while depletion-mode HEMTs are suitable for RF applications. Power electronics applications utilize GaN/AlGaN HEMTs with dielectric insulators as a means of achieving a large gate voltage swing for high current density and low on-resistance. The dielectric insulators also suppress gate leakage, but at the expense of substantial interface charge density and the potential for hot electrons inducing unwanted trapped charges in the dielectric. These latter effects make gates employing dielectric insulators unsuitable for RF applications with GaN/AlGaN HEMTs.Al y Ga 1-y N/Al x Ga 1-x N HEMTs with high Al in the channel, x = 0.7 and larger, have promising figures of merit and are candidates for next generation power and RF applications. 1,7,11,12 With a bandgap of >5.8 eV, the Al 0.85 Ga 0.15 N barrier is practically an insulator, but since it is combined with a modest conduction band offset to the Al x Ga 1-x N channel it has both insulator and Schottky-like properties. As a crystallographic insulator-like material, it has potential for a very good interface with nearly lattice matched Al x Ga 1-x N channel adjacent to the 2-dimensional electron gas (2DEG). Even as a Schottky barrier it can have a large turn-on voltage to enhance the voltage swing and current drive capability. Although promising, Al x Ga 1-x N channel HEMTs lack maturity and do not yet match the high current density of AlGaN/GaN HEMTs due both to the difficulty of achieving good ohmic contacts and the lack of aggressive dimensional scaling to compensate for limitations of the low-field electron mobility, which is limited by alloy scattering.In this work ...

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Section: Resultsmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9] Their promise derives from the large critical electric field, which scales as a power law with the bandgap of the material, 10 e.g. E C ∼ E G 2.5 (the exact dependence is a topic of active research) and provides favorable power and RF figures of merit.…”

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confidence: 99%

Al_0.85Ga_0.15N/Al_0.70Ga_0.30N High Electron Mobility Transistors with Schottky Gates and Large On/Off Current Ratio over Temperature

Baca

Klein

Allerman

et al. 2017

ECS J. Solid State Sci. Technol.

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“…Here we take this to be a constant value of 10 13 cm −2 over the entire composition range, consistent with experimental reports on Al-rich AlGaN/AlGaN heterostructures. 4,5,7,9 Other authors have taken the approach that n s is proportional to E C , 18 which eliminates n s from the LFOM and makes it proportional to E C 3 rather than E C 2 . Thus, in such a situation the LFOM has the same dependence on critical field as the UFOM (UFOM = εμE C 3 /4 where ε is the dielectric constant of the semiconductor (F/cm) and μ is the bulk mobility).…”

Section: Derivation Of the Lfommentioning

confidence: 99%

Analysis of 2D Transport and Performance Characteristics for Lateral Power Devices Based on AlGaN Alloys

Coltrin

Baca

Kaplar

2017

ECS J. Solid State Sci. Technol.

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Predicted lateral power device performance as a function of alloy composition is characterized by a standard lateral device figure-ofmerit (LFOM) that depends on mobility, critical electric field, and sheet carrier density. The paper presents calculations of AlGaN electron mobility in lateral devices such as HEMTs across the entire alloy composition range. Alloy scattering and optical polar phonon scattering are the dominant mechanisms limiting carrier mobility. Due to the significant degradation of mobility from alloy scattering, at room temperature Al fractions greater than about 85% are required for improved LFOM relative to GaN using a conservative sheet charge density of 1 × 10 13 cm −2 . However, at higher temperatures at which AlGaN power devices are anticipated to operate, this "breakeven" composition decreases to about 65% at 500 K, for example. For high-frequency applications, the Johnson figure-of-merit (JFOM) is the relevant metric to compare potential device performance across materials platforms. At room temperature, the JFOM for AlGaN alloys is predicted to surpass that of GaN for Al fractions greater than about 40%.

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“…Lately, the most advanced nitride HEMTs have achieved initial commercialization up to 650 V. However, with the maturity of device fabrication technology, it has become increasingly difficult to further scaling up the breakdown voltages (BV) and improving the device reliability at high temperatures. Therefore, in view of the larger bandgap and superior thermal stability of AlGaN over GaN, AlGaN channel devices have been proposed as promising candidate to further improve the performance limits of nitride HEMTs in high-voltage and high-temperature applications [6][7][8][9][10][11][12][13]. Recently, the successful implementation of AlGaN channel metal-oxidesemiconductor field-effect-transistors (MOSFETs) have also been reported [14].…”

Section: Main Textmentioning

confidence: 99%

High-performance AlGaN double channel HEMTs with improved drain current density and high breakdown voltage

Zhang

Wang

et al. 2020

Preprint

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In this work, for the first time, AlGaN double channel heterostructure is proposed and grown by metal organic chemical vapor deposition (MOCVD), and high-performance AlGaN double channel high electron mobility transistors (HEMTs) are fabricated and investigated. The implementation of double channel feature effectively improves the transport properties of AlGaN channel heterostructures. On one hand, the total two dimensional electron gas (2DEG) density is promoted due to the double potential wells along the vertical direction and the enhanced carrier confinement. On the other hand, the average 2DEG density in each channel is reduced, and the mobility is elevated resulted from the suppression of carrier-carrier scattering effect. As a result, the maximum drain current density (Imax) of AlGaN double channel HEMTs reaches 473 mA/mm with gate voltage of 0V. Moreover, the superior breakdown performance of the AlGaN double channel HEMTs is also demonstrated. These results not only show the great application potential of AlGaN double channel HEMTs in microwave power electronics, but also develops a new thinking for the studies of group III nitride based electronic devices.

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High Electron Mobility Transistors With Al_0.65Ga_0.35N Channel Layers on Thick AlN/Sapphire Templates

Cited by 53 publications

References 18 publications

Al_0.85Ga_0.15N/Al_0.70Ga_0.30N High Electron Mobility Transistors with Schottky Gates and Large On/Off Current Ratio over Temperature

Al_0.85Ga_0.15N/Al_0.70Ga_0.30N High Electron Mobility Transistors with Schottky Gates and Large On/Off Current Ratio over Temperature

Analysis of 2D Transport and Performance Characteristics for Lateral Power Devices Based on AlGaN Alloys

High-performance AlGaN double channel HEMTs with improved drain current density and high breakdown voltage

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High Electron Mobility Transistors With Al0.65Ga0.35N Channel Layers on Thick AlN/Sapphire Templates

Cited by 53 publications

References 18 publications

Al0.85Ga0.15N/Al0.70Ga0.30N High Electron Mobility Transistors with Schottky Gates and Large On/Off Current Ratio over Temperature

Al0.85Ga0.15N/Al0.70Ga0.30N High Electron Mobility Transistors with Schottky Gates and Large On/Off Current Ratio over Temperature

Analysis of 2D Transport and Performance Characteristics for Lateral Power Devices Based on AlGaN Alloys

High-performance AlGaN double channel HEMTs with improved drain current density and high breakdown voltage

Contact Info

Product

Resources

About

High Electron Mobility Transistors With Al_0.65Ga_0.35N Channel Layers on Thick AlN/Sapphire Templates

Al_0.85Ga_0.15N/Al_0.70Ga_0.30N High Electron Mobility Transistors with Schottky Gates and Large On/Off Current Ratio over Temperature

Al_0.85Ga_0.15N/Al_0.70Ga_0.30N High Electron Mobility Transistors with Schottky Gates and Large On/Off Current Ratio over Temperature