Low resistive Au-free, Ta-based, recessed ohmic contacts to InAlN/AlN/GaN heterostructures

Bergsten, Johan; Malmros, Anna; Tordjman, M.; Gamarra, Piero; Lacam, C.; Forte-Poisson, M.A. di; Rorsman, Niklas

doi:10.1088/0268-1242/30/10/105034

Cited by 25 publications

(15 citation statements)

References 31 publications

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“…The recess etch was made with a low power Cl/Ar-plasma, and the metal stack was Ta/Al/Ta (10/280/20 nm). [12][13][14] After annealing at 550 C, the contact resistance was measured to be 0.33 X Â mm. The gates were defined in a two-step electron-beam lithography process.…”

Section: à3mentioning

confidence: 99%

Carbon doped GaN buffer layer using propane for high electron mobility transistor applications: Growth and device results

Bergsten

Nilsson

et al. 2015

Applied Physics Letters

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The creation of a semi insulating (SI) buffer layer in AlGaN/GaN High Electron Mobility Transistor (HEMT) devices is crucial for preventing a current path beneath the two-dimensional electron gas (2DEG). In this investigation, we evaluate the use of a gaseous carbon gas precursor, propane, for creating a SI GaN buffer layer in a HEMT structure. The carbon doped profile, using propane gas, is a two stepped profile with a high carbon doping (1.5 × 1018 cm−3) epitaxial layer closest to the substrate and a lower doped layer (3 × 1016 cm−3) closest to the 2DEG channel. Secondary Ion Mass Spectrometry measurement shows a uniform incorporation versus depth, and no memory effect from carbon doping can be seen. The high carbon doping (1.5 × 1018 cm−3) does not influence the surface morphology, and a roughness root-mean-square value of 0.43 nm is obtained from Atomic Force Microscopy. High resolution X-ray diffraction measurements show very sharp peaks and no structural degradation can be seen related to the heavy carbon doped layer. HEMTs are fabricated and show an extremely low drain induced barrier lowering value of 0.1 mV/V, demonstrating an excellent buffer isolation. The carbon doped GaN buffer layer using propane gas is compared to samples using carbon from the trimethylgallium molecule, showing equally low leakage currents, demonstrating the capability of growing highly resistive buffer layers using a gaseous carbon source.

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Section: à3mentioning

confidence: 99%

Carbon doped GaN buffer layer using propane for high electron mobility transistor applications: Growth and device results

Bergsten

Nilsson

et al. 2015

Applied Physics Letters

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“…Recessed and Ta-based ohmic contacts produced contact resistances of %0.3 Ω mm as extracted from transmission line measurements for all samples. [21][22][23] HEMTs with gate lengths (L g ) of 40, 70, 100, 150, and 200 nm, a gatesource distance (L GS ) of 1 μm, gate-drain distances (L GD ) of 1 and 2.5 μm, and a gate width of 2 Â 50 um were fabricated. The dimensions were verified with a scanning electron microscope.…”

Section: Methodsmentioning

confidence: 99%

Impact of the Channel Thickness on Electron Confinement in MOCVD‐Grown High Breakdown Buffer‐Free AlGaN/GaN Heterostructures

Chen¹,

Wen²,

Thorsell

et al. 2022

Physica Status Solidi (a)

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The 2D electron gas (2DEG) confinement on high electron mobility transistor (HEMT) heterostructures with a thin undoped GaN channel layer on the top of a grain‐boundary‐free AlN nucleation layer is studied. This is the first time demonstration of a buffer‐free epi‐structure grown with metal–organic chemical vapor deposition with thin GaN channel thicknesses, ranging from 250 to 150 nm, without any degradation of the structural quality and 2DEG properties. The HEMTs with a gate length of 70 nm exhibit good DC characteristics with peak transconductances of 500 mS mm−1 and maximum saturated drain currents above 1 A mm−1. A thinner GaN channel layer improves 2DEG confinement because of the enhanced effectiveness of the AlN nucleation layer acting as a back‐barrier. An excellent drain‐induced barrier lowering of only 20 mV V−1 at a VDS of 25 V and an outstanding critical electric field of 0.95 MV cm−1 are demonstrated. Good large‐signal performance at 28 GHz with output power levels of 2.0 and 3.2 W mm−1 and associated power‐added efficiencies of 56% and 40% are obtained at a VDS of 15 and 25 V, respectively. These results demonstrate the potential of sub‐100 nm gate length HEMTs on a buffer‐free GaN‐on‐SiC heterostructure.

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“…%) typically require a high alloy temperature while, in agreement with our observations, the optimum alloy temperature is typically in the 500-600°C range for Al-rich ohmic metal stacks. 16) For both Au-containing [20][21][22][23][24] and Au-free ohmic contacts, [25][26][27][28][29][30][31] it was shown that the ohmic contact resistance can be further improved by partial or complete removal of the AlGaN barrier. Indeed, because of the insulating nature of the AlGaN barrier, ohmic contact formation relies partly on carrier tunneling across this barrier, and partial or complete removal of the AlGaN barrier was shown to facilitate ohmic contact formation.…”

Section: Introductionmentioning

confidence: 99%

Impact of crystal orientation on ohmic contact resistance of enhancement-mode p-GaN gate high electron mobility transistors on 200 mm silicon substrates

Hove¹,

Posthuma²,

Geens³

et al. 2018

Jpn. J. Appl. Phys.

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p-GaN gate enhancement mode power transistors were processed in a Si CMOS processing line on 200 mm Si(111) substrates using Au-free metallization schemes. Si/Ti/Al/Ti/TiN ohmic contacts were formed after full recessing of the AlGaN barrier, followed by a HCl-based wet cleaning step. The electrical performance of devices aligned to the ½11 20 and the perpendicular ½1 100 directions was compared. The ohmic contact resistance was decreased from 1 Ω&mm for the ½11 20 direction to 0.35 Ω&mm for the ½1 100 direction, resulting in an increase of the drain saturation current from 0.5 to 0.6 A/mm, and a reduction of the on-resistance from 6.4 to 5.1 Ω&mm. Moreover, wafer mapping of the device characteristics over the 200 mm wafer showed a tighter statistical distribution for the ½1 100 direction. However, by using an optimized sulfuric/ammonia peroxide (SPM/APM) cleaning step, the ohmic contact resistance could be lowered to 0.3 Ω&mm for both perpendicular directions.

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Low resistive Au-free, Ta-based, recessed ohmic contacts to InAlN/AlN/GaN heterostructures

Cited by 25 publications

References 31 publications

Carbon doped GaN buffer layer using propane for high electron mobility transistor applications: Growth and device results

Carbon doped GaN buffer layer using propane for high electron mobility transistor applications: Growth and device results

Impact of the Channel Thickness on Electron Confinement in MOCVD‐Grown High Breakdown Buffer‐Free AlGaN/GaN Heterostructures

Impact of crystal orientation on ohmic contact resistance of enhancement-mode p-GaN gate high electron mobility transistors on 200 mm silicon substrates

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