Electrical properties, microstructure, and thermal stability of Ta-based ohmic contacts annealed at low temperature for GaN HEMTs

Malmros, Anna; Blanck, H.; Rorsman, Niklas

doi:10.1088/0268-1242/26/7/075006

Cited by 83 publications

(55 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Apart from a low contact resistance a smooth surface morphology is important for the detection of alignment marks and scaling of the drain/source-gate dis-tance. It has been demonstrated previously that Ta/Al/Ta metallization can produce low-resistive ohmic contacts to AlGaN/GaN when annealed at the comparatively very low temperature of 550 °C [3]. In this study we show that also InAlN/AlN/GaN HEMTs may be fabricated with Ta-based ohmic contacts.…”

Section: Introductionsupporting

confidence: 53%

Evaluation of an InAlN/AlN/GaN HEMT with Ta‐based ohmic contacts and PECVD SiN passivation

Malmros

Gamarra

Thorsell

et al. 2014

Phys. Status Solidi C

View full text Add to dashboard Cite

An InAlN/AlN/GaN HEMT with Au‐free Ta‐based ohmic contacts and a high‐quality PECVD SiN pas‐sivation is reported. The ohmic contacts were annealed at 550 °C, resulting in a contact resistance of 0.64 Ωmm. The gate length was 50 nm. The device performance and the process were evaluated by performing DC‐, pulsed IV‐, RF‐, and load‐pull measurements. It was observed that current slump was effectively mitigated by the passivation layer. The DC channel current density increased by 71 % to 1170 mA/mm at the knee of the IV curve, and the transconductance increased from 382 to 477 mS/mm after passivation. At the same time the gate leakage increased, and the extrinsic fmax decreased from 207 to 140 GHz. Output powers of 4.1 and 3.5 W/mm were measured after passivation at 31 and 40 GHz, respectively. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

show abstract

Section: Introductionsupporting

confidence: 53%

Evaluation of an InAlN/AlN/GaN HEMT with Ta‐based ohmic contacts and PECVD SiN passivation

Malmros

Gamarra

Thorsell

et al. 2014

Phys. Status Solidi C

View full text Add to dashboard Cite

show abstract

“…Ohmic contacts were formed by self-aligned recessing, metalstack evaporation, and liftoff. The structure was recessed to a depth just above the AlN exclusion layer [19] and a [20]. The gates were defined in a twostep electron beam lithography process.…”

Section: B Hemt Fabricationmentioning

confidence: 99%

Dispersive Effects in Microwave AlGaN/AlN/GaN HEMTs With Carbon-Doped Buffer

Gustafsson

Chen

Bergsten

et al. 2015

IEEE Trans. Electron Devices

View full text Add to dashboard Cite

Aluminium gallium nitride (AlGaN)/GaN high-electron mobility transistor performance is to a large extent affected by the buffer design, which, in this paper, is varied using different levels of carbon incorporation. Three epitaxial structures have been fabricated: 1) two with uniform carbon doping profile but different carbon concentration and 2) one with a stepped doping profile. The epitaxial structures have been grown on 4H-SiC using hot-wall metal-organic chemical vapor deposition with residual carbon doping. The leakage currents in OFF-state at 10 V drain voltage were in the same order of magnitude (10 −4 A/mm) for the high-doped and stepped-doped buffer. The high-doped material had a current collapse (CC) of 78.8% compared with 16.1% for the stepped-doped material under dynamic I-V conditions. The low-doped material had low CC (5.2%) but poor buffer isolation. Trap characterization revealed that the high-doped material had two trap levels at 0.15 and 0.59 eV, and the low-doped material had one trap level at 0.59 eV.Index Terms-Current collapse (CC), dispersion, gallium nitride (GaN), high-electron mobility transistor (HEMT), trap levels.

show abstract

“…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

View full text Add to dashboard Cite

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.

show abstract

Electrical properties, microstructure, and thermal stability of Ta-based ohmic contacts annealed at low temperature for GaN HEMTs

Cited by 83 publications

References 24 publications

Evaluation of an InAlN/AlN/GaN HEMT with Ta‐based ohmic contacts and PECVD SiN passivation

Evaluation of an InAlN/AlN/GaN HEMT with Ta‐based ohmic contacts and PECVD SiN passivation

Dispersive Effects in Microwave AlGaN/AlN/GaN HEMTs With Carbon-Doped Buffer

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

Contact Info

Product

Resources

About