Barrier Thickness Dependence of Electrical Properties and DC Device Characteristics of AlGaN/GaN Heterostructure Field-Effect Transistors Grown by Plasma-Assisted Molecular-Beam Epitaxy
TL;DR: In this paper, the authors report on the barrier thickness dependence of the electrical properties and DC device characteristics of Al0.4Ga0.6N/GaN heterostructure field effect transistors (HFETs).
Abstract: We report on the barrier thickness dependence of the electrical properties and DC device characteristics of Al0.4Ga0.6N/GaN heterostructure field-effect transistors (HFETs). The HFET structures with 8–25-nm-thick AlGaN barrier layers were grown on sapphire substrates by plasma-assisted molecular-beam epitaxy. All of the fabricated HFET devices with a gate length of 1 µm showed a good DC performance and an excellent pinch-off characteristic. The extrinsic transconductance of the HFET devices increased from 185 to 360 mS/mm with decreasing AlGaN barrier thickness from 25 to 8 nm, while the maximum drain current for a gate bias of +1.0 V decreased from 1.1 to 0.68 A/mm.
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TL;DR: In this article, the characteristics of high-electron mobility transistors with barrier thickness between 33 and 3 nm, which are grown on sapphire substrates by metal-organic chemical vapor deposition, were discussed.
Abstract: We discuss the characteristics of high-electron mobility transistors with barrier thicknesses between 33 and 3 nm, which are grown on sapphire substrates by metal-organic chemical vapor deposition. The maximum drain current (at VG = 2.0 V) decreased with decreasing barrier thickness due to the gate forward drive limitation and residual surface-depletion effect. Full pinchoff and low leakage are observed. Even with 3-nm ultrathin barrier, the heterostructure and contacts are thermally highly stable (up to 1000degC).
121 citations
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...However, in planar AlGaN/GaN devices, the channel sheet carrier density starts to decrease already at a barrier thickness of around 20 nm [7], [8]....
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TL;DR: In this paper, the authors employed two novel techniques, which were thin, high-Al-composition AlGaN barrier layers and SiN gate-insulating, passivation layers formed by catalytic chemical vapor deposition, to enhance high-frequency device characteristics by suppressing the short channel effect.
Abstract: Al/sub 0.4/Ga/sub 0.6/N/GaN heterostructure field-effect transistors (HFETs) with an AlGaN barrier thickness of 8 nm and a gate length (L/sub G/) of 0.06-0.2 /spl mu/m were fabricated on a sapphire substrate. We employed two novel techniques, which were thin, high-Al-composition AlGaN barrier layers and SiN gate-insulating, passivation layers formed by catalytic chemical vapor deposition, to enhance high-frequency device characteristics by suppressing the short channel effect. The HFETs with L/sub G/=0.06-0.2 /spl mu/m had a maximum drain current density of 1.17-1.24 A/mm at a gate bias of +1.0 V and a peak extrinsic transconductance of 305-417 mS/mm. The current-gain cutoff frequency (f/sub T/) was 163 GHz, which is the highest value to have been reported for GaN HFETs. The maximum oscillation frequency (f/sub max/) was also high, and its value derived from the maximum stable gain or unilateral gain was 192 or 163 GHz, respectively.
107 citations
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...the high Al composition enhances polarization in AlGaN and increases sheet electron density [4]....
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TL;DR: In this paper, the effect of SiN surface passivation by catalytic chemical vapor deposition (Cat-CVD) on Al/sub 0.4/N-GaN heterostructure field effect transistors (HFETs) was investigated.
Abstract: The effect of SiN surface passivation by catalytic chemical vapor deposition (Cat-CVD) on Al/sub 0.4/Ga/sub 0.6/N-GaN heterostructure field-effect transistors (HFETs) was investigated. The channel sheet resistance was reduced by the passivation due to an increase in electron density, and the device characteristics of the thin-barrier HFETs were significantly improved by the reduction of source and drain resistances. The AlGaN(8 nm)-AlN(1.3 nm)-GaN HFET device with a source/drain distance of 3 /spl mu/m and a gate length of 1 /spl mu/m had a maximum drain current density of 0.83 A/mm at a gate bias of +1.5 V and an extrinsic maximum transconductance of 403 mS/mm. These results indicate the substantial potential of Cat-CVD SiN-passivated AlGaN-GaN HFETs with thin and high Al composition barrier layers.
63 citations
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...with the same length of the S/D separation and gate have been described in the previous report [5]....
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TL;DR: In this article, a SiN-passivated T-gate AlGaN/GaN high-electron-mobility transistors (HEMTs) with a 0.15-µm gate were fabricated on a Si substrate with an 8-nm-thick AlGAN barrier, which exhibited a unity current gain cutoff frequency fT of 63 GHz and maximum oscillation frequency fmax of 124 GHz.
Abstract: AlGaN/GaN high-electron-mobility transistors (HEMTs) with a 0.15-µm gate were fabricated on a Si substrate with an 8-nm-thick AlGaN barrier. The device exhibited a unity current gain cutoff frequency fT of 63 GHz and maximum oscillation frequency fmax of 124 GHz. Its three-terminal OFF-state breakdown voltage BVgd is as high as 132 V. The estimated Johnson's figure of merit (=BVgd × fT) is 8.32 × 1012 V/s (8.32 THzV), which is the highest value ever reported for a conventional SiN-passivated T-gate AlGaN/GaN HEMTs on a Si substrate without an additional field plate or gamma gate.
32 citations
TL;DR: Al-gated AlGaN∕GaN high-electron-mobility transistors (HEMTs) on 4in. Si were fabricated by inserting 3nm of Al metal as a gate prior to the deposition of Pd∕Ti∕Au as discussed by the authors.
Abstract: AlGaN∕GaN high-electron-mobility transistors (HEMTs) on 4in. Si were fabricated by inserting 3nm of Al metal as a gate prior to the deposition of Pd∕Ti∕Au. The increase of drain current (IDSmax) density and decrease of extrinsic transconductance (gmmax) have been observed in the Al-gated AlGaN∕GaN HEMTs. The increase of IDmax is due to the increase of two-dimensional electron gas sheet carrier density, which was confirmed by capacitance-voltage (C-V) measurements. Moreover, the Al layer inserted-gate HEMT exhibited negative threshold voltage (Vth) shift. The Al and AlGaN interface shows Al-based oxide layer which was confirmed by Auger electron spectrum and x-ray photoelectron spectrum.
25 citations
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TL;DR: In this paper, a sub-50-nm-gate i-AlGaN/GaN high electron mobility transistors (HEMTs) were fabricated on sapphire and measured their DC and RF characteristics at room temperature.
Abstract: We fabricated sub-50-nm-gate i-AlGaN/GaN high electron mobility transistors (HEMTs) on sapphire and measured their DC and RF characteristics at room temperature. The fabricated HEMTs exhibited true device operation and good pinch-off characteristics down to a gate length Lg of 25 nm. For the HEMTs with a source–drain spacing Lsd of 2 μm, we obtained the Lg dependence of the cutoff frequency fT under a drain–source voltage Vds of 3 V. The peak fT was measured to be 102 GHz at Lg = 35 nm. At Lg = 25 nm, fT started to decrease due to the short-channel effect. The highest fT of 110 GHz was obtained by reducing Lsd from 2 to 1.5 μm and by increasing Vds from 3 to 4 V. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
39 citations
01 May 2003
22 citations
TL;DR: In this paper, a recessed gate AlGaN/GaN high electron mobility transistors (HEMTs) were fabricated on a sapphire substrate and optimized the layer structure and the electrode arrangement of the HEMT.
Abstract: Recessed gate AlGaN/GaN high electron mobility transistors (HEMTs) grown on sapphire substrate have been fabricated. In order to improve FET performances, we optimized the layer structure and the electrode arrangement of the HEMT, and hence 0.15 μm gate-length AlGaN/GaN-HEMTs with recessed gate were successfully fabricated and the obtained transconductance was as high as 450 mS/mm. In this paper we describe the improvement of HEMT layer structures on sapphire substrate, the optimisation of an offset arrangement of gate electrodes, and the results of DC/RF measurements of our HEMTs. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
20 citations
TL;DR: In this paper, the improved performance of AlGaN/GaN heterojunction field effect transistors using a delta-doping approach along with an AlN binary barrier is reported.
Abstract: The improved performance of AlGaN/GaN heterojunction field-effect transistors using a delta-doping approach along with an AlN binary barrier is reported. Low-pressure metalorganic chemical vapor deposition was used to grow the epitaxial heterostructures on semi-insulating SiC substrates. The maximum carrier mobility of µ=1,066 cm2/V-s and sheet carrier density of ns~2.30×1013 cm-2 yields a large nsµ product of 2.45×1016 V-s. Devices with 0.15 µm gate lengths exhibited a maximum current density of IDSmax=1.82 A/mm (at VG=+1 V) and a peak transconductance of gm=331 mS/mm. Furthermore, fT~55 GHz and fmax~115 GHz were measured.
8 citations