Optimization of recessed ohmic contacts for AlGaN/AlN/GaN heterostructures using C(V) characterization of MSHM structures

Fagerlind, Martin; Rorsman, Niklas

doi:10.1002/pssc.201001053

Cited by 10 publications

(12 citation statements)

References 8 publications

(9 reference statements)

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“…Additional recess etching into the AlGaN barrier for contact metallization processes becomes necessary to reduce the contact resistance. 10,11 In this work, we show that the 2DEG mobility can be greatly improved in metalorganic chemical vapor deposition (MOCVD)-grown AlGaN/GaN heterostructures by sharpening the interface, without inserting an AlN ex layer. The effect of different AlGaN/GaN interface structures on the 2DEG properties is presented, utilizing high-resolution scanning transmission electron microscopy (STEM).…”

mentioning

confidence: 87%

Room-temperature mobility above 2200 cm2/V·s of two-dimensional electron gas in a sharp-interface AlGaN/GaN heterostructure

Chen

Persson

Nilsson

et al. 2015

Applied Physics Letters

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mentioning

confidence: 87%

Room-temperature mobility above 2200 cm2/V·s of two-dimensional electron gas in a sharp-interface AlGaN/GaN heterostructure

Chen

Persson

Nilsson

et al. 2015

Applied Physics Letters

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“…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

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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.

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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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Optimization of recessed ohmic contacts for AlGaN/AlN/GaN heterostructures using C(V) characterization of MSHM structures

Cited by 10 publications

References 8 publications

Room-temperature mobility above 2200 cm2/V·s of two-dimensional electron gas in a sharp-interface AlGaN/GaN heterostructure

Room-temperature mobility above 2200 cm2/V·s of two-dimensional electron gas in a sharp-interface AlGaN/GaN heterostructure

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

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