Effect of Gate Leakage in the Subthreshold Characteristics of AlGaN/GaN HEMTs

Chung, J. W.; Roberts, John C.; Piner, Edwin L.; Palacios, Tomás

doi:10.1109/led.2008.2005257

Cited by 191 publications

(96 citation statements)

References 11 publications

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“…3 are not matched in AlGaN/GaN HEMTs with Schottky gates, and therefore gate insulator dielectrics are often used to achieve low leakage and high breakdown. [24][25][26][27] Although effective in reducing gate and subthreshold leakage, gate insulators in III-N materials bring about effects associated with their high interface state trap densities, including a reduction in transconductance and a negative shift in V TH .…”

Section: Resultsmentioning

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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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%

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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“…18 And the observed improvements in subthreshold characteristics of Al 2 O 3 /AlInN/GaN MOS-HEMT also suggest such high quality gate insulator. 19 As shown in Fig. 2(b), the AlInN/GaN SB-HEMT and MOS-HEMT exhibits complete pinch-off characteristics with the threshold voltage (V th ) of À4 and À7 V, respectively.…”

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confidence: 91%

Enhanced two dimensional electron gas transport characteristics in Al2O3/AlInN/GaN metal-oxide-semiconductor high-electron-mobility transistors on Si substrate

Freedsman

Watanabe

Urayama

et al. 2015

Applied Physics Letters

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The authors report on Al2O3/Al0.85In0.15N/GaN Metal-Oxide-Semiconductor High-Electron-Mobility Transistor (MOS-HEMT) on Si fabricated by using atomic layer deposited Al2O3 as gate insulator and passivation layer. The MOS-HEMT with the gate length of 2 μm exhibits excellent direct-current (dc) characteristics with a drain current maximum of 1270 mA/mm at a gate bias of 3 V and an off-state breakdown voltage of 180 V for a gate-drain spacing of 4 μm. Also, the 1 μm-gate MOS-HEMT shows good radio-frequency (rf) response such as current gain and maximum oscillation cut-off frequencies of 10 and 34 GHz, respectively. The capacitance-voltage characteristics at 1 MHz revealed significant increase in two-dimensional electron gas (2DEG) density for the MOS-HEMT compared to conventional Schottky barrier HEMTs. Analyses using drain-source conductivity measurements showed improvements in 2DEG transport characteristics for the MOS-HEMT. The enhancements in dc and rf performances of the Al2O3/Al0.85In0.15N/GaN MOS-HEMT are attributed to the improvements in 2DEG characteristics.

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“…The devices are intentionally left unpassivated. Usually, the sub-threshold drain leakage current, a limiting factor for device performance, has strong dependence on the reverse bias gate current [11]. The reverse bias gate leakage current of the Schottky device at V GS = −40 V is about 20 μA/mm, representing a low value.…”

mentioning

confidence: 99%

High f _T and f _MAX for 100 nm unpassivated rectangular gate AlGaN/GaN HEMT on high resistive silicon (111) substrate

et al. 2015

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A high current gain cutoff frequency ( f T ) of 90 GHz and a peak maximum oscillation frequency ( f MAX ) as high as 150 GHz are reported for a rectangular-shaped gate AlGaN/GaN high-electron mobility transistor (HEMT) on a high resistive silicon (HR-Si) substrate. The combined high f T /f MAX values for 100 nm unpassivated gate device demonstrate the high-quality heterostructure on silicon substrate. The reported high-performance RF device characteristics are comparable and even superior to the existing passivated AlGaN/ GaN HEMTs of similar gate length. In addition, good DC characteristics have been recorded with the drain current density and an extrinsic transconductance of 0.6 A/mm and 157 mS/mm, respectively.Introduction: With the remarkable combination of superior physical properties and highly scaled device geometries, GaN-based highelectron mobility transistors (HEMTs) remain a good choice of device for high-power, wideband and high-temperature applications [1,2]. The high breakdown field, high-electron saturation velocity and large sheet carrier densities together with the implementation of short gate geometries (i.e. L g < 0.1 μm) make the GaN system the leading contender for solid-state power amplifiers at the microwave-and millimetrewave frequency range (30-300 GHz) [3][4][5]. Compared with the mature GaN technology on sapphire and SiC substrates, the handling of high power densities of GaN on the high resistive silicon (HR-Si) substrate promises a low-cost solution, provided the high-quality device grade GaN heterostructure is realised.The emerging reports on the millimetre-wave frequency performances of AlGaN/GaN-based HEMTs showcase the high-frequency solution of GaN on Si. For example, a fully passivated 75 nm gate AlGaN/GaN HEMT on Si demonstrates that a high f T /f MAX = 152/149 GHz with a large signal operation yields an output power of 2 W/mm at 40 GHz [6]. An attractive RF performance has been reported for GaN on Si with f T /f MAX = 100/206 GHz for a T-shaped 90 nm gate length [7]. A similar gate geometry AlGaN/GaN HEMT with the incorporation of a AlGaN back barrier yielding a high breakdown voltage (BV = 100 V) and a high f MAX of 226 GHz with a simultaneous f T of 63 GHz has been reported for L g = 160 nm [8]. It is obvious that the enhancement of f T / f MAX for the AlGaN/GaN HEMT is still a major concern although high f MAX has been achieved for highly scaled devices with SiN passivation. Only a few reports have been published for 0.1 μm gate AlGaN/ GaN HEMT technology exhibiting high f T /f MAX with passivation [9, 10]. Hence, further performance enhancement for millimetre-wave applications warrants the implementation of deeply scaled devices which involves complicated gate geometries and process techniques.In this Letter, we report a simple AlGaN/GaN HEMT heterostructure with a rectangular shaped 0.1 μm gate demonstrating good performance in both the DC and the RF regimes.

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Effect of Gate Leakage in the Subthreshold Characteristics of AlGaN/GaN HEMTs

Cited by 191 publications

References 11 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

Enhanced two dimensional electron gas transport characteristics in Al2O3/AlInN/GaN metal-oxide-semiconductor high-electron-mobility transistors on Si substrate

High f _T and f _MAX for 100 nm unpassivated rectangular gate AlGaN/GaN HEMT on high resistive silicon (111) substrate

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Effect of Gate Leakage in the Subthreshold Characteristics of AlGaN/GaN HEMTs

Cited by 191 publications

References 11 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

Enhanced two dimensional electron gas transport characteristics in Al2O3/AlInN/GaN metal-oxide-semiconductor high-electron-mobility transistors on Si substrate

High f T and f MAX for 100 nm unpassivated rectangular gate AlGaN/GaN HEMT on high resistive silicon (111) substrate

Contact Info

Product

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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

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

High f _T and f _MAX for 100 nm unpassivated rectangular gate AlGaN/GaN HEMT on high resistive silicon (111) substrate