Self-aligned-gate GaN-HEMTs with heavily-doped n&lt;sup&gt;&amp;#x002B;&lt;/sup&gt;-GaN ohmic contacts to 2DEG

Shinohara, Kazuhiko; Regan, D.; Corrion, A.; Brown, David F.; Tang, Yan; Wong, Joel; Candia, G. de; Schmitz, A.; Fung, Helen; Kim, S.; Micovic, M.

doi:10.1109/iedm.2012.6479113

Cited by 52 publications

(45 citation statements)

References 3 publications

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“…State-of-art gallium nitride based electronic devices have demonstrated excellent performance in highfrequency and high-power applications [1][2][3][4][5] . These devices are on thick GaN buffer layers, most of which are on SiC substrates for efficient thermal dissipation.…”

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confidence: 99%

Strained GaN quantum-well FETs on single crystal bulk AlN substrates

Ganguly

et al. 2017

Applied Physics Letters

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We report the first realization of molecular beam epitaxy grown strained GaN quantum well field-effect transistors on single-crystal bulk AlN substrates. The fabricated double heterostructure FETs exhibit a twodimensional electron gas (2DEG) density in excess of 2×10 13 /cm 2 . Ohmic contacts to the 2DEG channel were formed by n + GaN MBE regrowth process, with a contact resistance of 0.13 Ω·mm. Raman spectroscopy using the quantum well as an optical marker reveals the strain in the quantum well, and strain relaxation in the regrown GaN contacts. A 65-nm-long rectangular-gate device showed a record high DC drain current drive of 2.0 A/mm and peak extrinsic transconductance of 250 mS/mm. Small-signal RF performance of the device achieved current gain cutoff frequency f T ∼ 120 GHz. The DC and RF performance demonstrate that bulk AlN substrates offer an attractive alternative platform for strained quantum well nitride transistors for future high-voltage and high-power microwave applications.State-of-art gallium nitride based electronic devices have demonstrated excellent performance in highfrequency and high-power applications 1-5 . These devices are on thick GaN buffer layers, most of which are on SiC substrates for efficient thermal dissipation. The heteroepitaxially grown GaN layers inherently incorporate high density of dislocations (typically ∼ 10 9 /cm 2 ), which give rise to reliability issues and degrade breakdown characteristics.In this letter we show that thin strained GaN quantum well double heterostructures on bulk AlN substrates offer an attractive alternative approach for high-performance nitride electronics. To meet the scaling requirements for high-speed high-power RF applications, tight electrostatic control and quantum confinement of charge carriers are highly desired. The wide direct band gap of AlN (∼6.2 eV) and its large band offset with GaN offers the maximal vertical confinement of carriers in nitride channels. The large polarization charge of AlN induces high density two-dimensional electron gases (2DEG) in the quantum well, which is desired for high current drive and lateral scaling of gate lengths. The thermal conductivity of AlN, estimated 6 to be as high as ∼340 W/m·K can be comparable 7 to that of SiC ∼370 W/m·K, and offers the potential benefit of reducing thermal boundary resistance. Thus AlN simultaneously satisfies the conflicting requirements of high thermal conductivity and high electrical resistivity for high-power microwave electronics. Importantly, the low dislocation density (∼ 10 4 /cm 2 ) of single-crystal bulk AlN substrates has the potential for defect-free channels and barriers in principle, which is a promising prospective for improving thermal robustness, reliability, breakdown, and noise characteristics of these devices 8 . The presence of a very thin GaN quantum well active region embedded in the AlN/GaN/AlN double heta) Electronic mail: djena@cornell.edu. erostructure also enables selective optical-marker based Raman metrology of strain 9 present in the active layer...

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confidence: 99%

Strained GaN quantum-well FETs on single crystal bulk AlN substrates

Ganguly

et al. 2017

Applied Physics Letters

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“…Monte Carlo simulations in GaN have predicted peak electron drift velocities as high as 3 x 10 7 cm/s, with comparatively lower saturation velocities up to ~ 2 x 10 7 cm/s, limited mainly by optical phonon scattering [7][8][9][10][11] . From the total time delay analysis in recent ultra-scaled GaN HEMT results, the average electron velocity, vave, of the devices was found to be in the range from 1 × 10 7 to 2.8 × 10 7 cm/s [1][2][3][4] .…”

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confidence: 99%

“…III-nitride high electron mobility transistors (HEMTs) have demonstrated promising high frequency operation for RF power amplifying applications [1][2][3][4] . Their high current and power gain capability, and further increases in the operation frequency could enable high power electronics in the mm-wave and THz regime.…”

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confidence: 99%

Density-dependent electron transport and precise modeling of GaN high electron mobility transistors

Bajaj

Shoron

Park

et al. 2015

Applied Physics Letters

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Abstract:We report on the direct measurement of two-dimensional sheet charge density dependence of electron transport in AlGaN/GaN high electron mobility transistors. Pulsed IV measurements established increasing electron velocities with decreasing sheet charge densities, resulting in saturation velocity of 1.9 x 10 7 cm/s at a low sheet charge density of 7.8 x 10 11 cm -2 . A new optical phonon emission-based electron velocity model for GaN is also presented. It accommodates stimulated LO phonon emission which clamps the electron velocity with strong electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs.a)

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“…Intensive work with normally-off AlGaN/GaN HEMTs is underway and different approaches, each with specific advantages and drawbacks, are pursued to appreciate normally-off operation. Examples are thin AlGaN barriers within the gate, fluorine treatment, GaN cap layers, the piezo neutralization technique, and hybrid MIS-HEMT structures [12][13][14][15][16][17][18][19][20][21]. Though AlGaN/GaN HEMTs have excellent RF power performance, it is still worth investigating potential ways to improve them to better meet the increasing demand for highpower microwave devices.…”

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confidence: 99%