Effect of gate length on DC performance of AlGaN/GaN HEMTs grown by MBE

Johnson, J. W.; Baca, Albert G.; Briggs, Ronald D.; Shul, R. J.; Wendt, Joel R.; Monier, C.; Ren, F.; Pearton, S. J.; Dabiran, A. M.; Wowchack, A. M.; Polley, C.J; Chow, P. P.

doi:10.1016/s0038-1101(01)00255-6

Cited by 37 publications

(15 citation statements)

References 22 publications

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“…[16][17][18][19][20][21] This problem is manifested by a collapse in the drain current or frequency dispersion in transconductance and output resistance, leading to severely reduced output power and power-added efficiency. Several mechanisms have been identified, including the presence of surface states between the gate and drain that deplete the channel in this region with time constant long enough to disrupt modulation of the channel charge during large signal operation or of trap states in the buffer layer.…”

Section: Resultsmentioning

confidence: 99%

“…[9][10][11][12]19 The RF performance of AlGaN/GaN HEMTs is a strong function of gate length (L G ), with a linear f T versus L G -1 relationship observed. 19,20 Karmalkar et al 21 noted that transistors with f max > f T can have useful power gains for f > f T and up to f max since a current gain of <1 may be compensated by a voltage gain > 1 for f T < f < f max . A typical working frequency for monolithic microwave integrated circuits (MMICs) based on HEMTs is expected to be 2/3 f max .…”

Section: Resultsmentioning

confidence: 99%

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Microwave Performance of AlGaN/GaN High-Electron-Mobility Transistors on Si/SiO2/Poly-SiC Substrates

Anderson

Ren

Kim

et al. 2007

Journal of Elec Materi

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The radiofrequency (RF) performance of AlGaN/GaN high-electron-mobility transistors (HEMTs) grown by molecular beam epitaxy (MBE) on Si-on-poly-SiC (SopSiC) substrates formed by the Smart-Cut TM process is reported. This provides a low-cost, high-thermal-conductivity substrate for power applications. HEMTs with a 0.5 lm gate length show cutoff frequencies (f T ) of 18 to 27 GHz for gate-to-drain distances of 3 to 32 lm and a maximum frequency of oscillation (f max ) of 43 to 47 GHz. The f max values are slightly lower than comparable devices on sapphire, SiC or Si alone. This approach looks promising for applications requiring cheap large-area substrates and better thermal management than provided by pure Si substrates alone.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Microwave Performance of AlGaN/GaN High-Electron-Mobility Transistors on Si/SiO2/Poly-SiC Substrates

Anderson

Ren

Kim

et al. 2007

Journal of Elec Materi

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“…AlGaN/GaN high electron mobility transistors (HEMTs) show great promise for high power and high frequency applications such as inverter units in hybrid electric vehicles, advanced radar systems, and satellite-based communication networks, due to their high sheet carrier concentration, high electron mobility, and radiation hardness. [1][2][3][4][5] In order to lower the cost of HEMTs, larger diameter substrates are needed. Currently, HEMT structures are grown on non-native sapphire, SiC and Si substrates or on native substrates of vapor phase epitaxy (VPE) GaN wafers.…”

mentioning

confidence: 99%

“…Currently, HEMT structures are grown on non-native sapphire, SiC and Si substrates or on native substrates of vapor phase epitaxy (VPE) GaN wafers. [4][5][6] HEMTs grown on sapphire substrates suffer from poor heat dissipation and higher defect density due to the relative larger lattice mismatch to GaN. SiC has very good thermal conductivity and has less lattice mismatch to GaN, but high quality semi-insulating SiC substrates are quite expensive.…”

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confidence: 99%

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AlGaN/GaN High Electron Mobility Transistor Grown and Fabricated on ZrTi Metallic Alloy Buffer Layers

Ren

Pearton

Ahn

et al. 2017

ECS J. Solid State Sci. Technol.

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AlGaN/GaN high electron mobility transistors (HEMTs) were demonstrated for structures grown on ZrTi metallic alloy buffer layers, which provided lattice matching of the in-plane lattice parameter ("a-parameter") to hexagonal GaN. The quality of the GaN buffer layer and HEMT structure were confirmed with X-ray 2θ and rocking scans as well as cross-section transmission electron microscopy (TEM) images. The X-ray 2θ scans showed full widths at half maximum (FWHM) of 0.06 • , 0.05 • and 0.08 • for ZrTi alloy, GaN buffer layer, and the entire HEMT structure, respectively. TEM of the lower section of the HEMT structure containing the GaN buffer layer and the AlN/ZrTi/AlN stack on the Si substrate showed that it was important to grow AlN on the top of ZrTi prior to growing the GaN buffer layer. The estimated threading dislocation (TD) density in the GaN channel layer of the HEMT structure was in the 10 8 cm −2 range. AlGaN/GaN high electron mobility transistors (HEMTs) show great promise for high power and high frequency applications such as inverter units in hybrid electric vehicles, advanced radar systems, and satellite-based communication networks, due to their high sheet carrier concentration, high electron mobility, and radiation hardness. [1][2][3][4][5] In order to lower the cost of HEMTs, larger diameter substrates are needed. Currently, HEMT structures are grown on non-native sapphire, SiC and Si substrates or on native substrates of vapor phase epitaxy (VPE) GaN wafers. [4][5][6] HEMTs grown on sapphire substrates suffer from poor heat dissipation and higher defect density due to the relative larger lattice mismatch to GaN. SiC has very good thermal conductivity and has less lattice mismatch to GaN, but high quality semi-insulating SiC substrates are quite expensive. Although Si substrates have fairly low cost and are available in larger diameters, the greater lattice mismatch to GaN requires the growth of thick AlGaN buffers prior to GaN growth to reduce the threading dislocation density.7-9 These thick AlGaN layers are usually defective and thermally resistive, which hinders device heat dissipation. Free-standing VPE-grown GaN wafers are currently limited to 2-3 diameter and are very expensive. Recently, it was reported that high quality GaN layers could be grown by RF plasma-assisted molecular beam epitaxy (PA-MBE) or metal-organic chemical vapor deposition (MOCVD) on high-quality, single-crystal ZrTi refractory metal alloys deposited by plasma sputtering on c-plane sapphire and Si substrates.10 These ZrTi refractory metal alloys are not only lattice-matched to GaN, but have similar coefficient of thermal expansion (CTE) to that of GaN. 10 By employing these ZrTi alloys as buffer layers, there is no need to grow thick AlGaN buffers, potentially allowing both photonic and electronic GaN-based device structure to be grown on large-area Si substrates, hence reducing the cost of device fabrication. AlGaN/GaN HEMT grown on sapphire with ZrTi alloys as buffer layers has been demonstrated. 11In this work, we...

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Analytical performance evaluation of AlGaN/GaN metal insulator semiconductor heterostructure field effect transistor and its comparison with conventional HFETs for high power microwave applications

Aggarwal

Agrawal

Gupta

et al. 2007

Micro & Optical Tech Letters

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In this work, a comprehensive analytical model for AlGaN/GaN MISHFET has been presented to evaluate the drain current characteristics, transconductance, and cut‐off frequency of the insulated device. The model takes into account polynomial dependence of sheet carrier density on position of quasi Fermi level to consider the quantum effects and to validate it from subthreshold to high conduction region. The effect of spontaneous and piezoelectric polarization at the AlGaN/GaN interface and parasitic source/drain resistances have also been incorporated in the analysis. Its advantages over conventional HFET structure are discussed in detail. For a MISHFET with quarter micron gate length, the cut‐off frequency is reported to be 52 GHz. The MISHFET shows remarkable 36% increase in drain saturation current. The model has a broad utility as it is equally applicable to HFETs as well. The present model is based on closed form expression and does not involve any fitting parameter. The results obtained are compared with experimental data and show excellent agreement, thereby proving the validity of the model. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 331–338, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23073

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Effect of gate length on DC performance of AlGaN/GaN HEMTs grown by MBE

Cited by 37 publications

References 22 publications

Microwave Performance of AlGaN/GaN High-Electron-Mobility Transistors on Si/SiO2/Poly-SiC Substrates

Microwave Performance of AlGaN/GaN High-Electron-Mobility Transistors on Si/SiO2/Poly-SiC Substrates

AlGaN/GaN High Electron Mobility Transistor Grown and Fabricated on ZrTi Metallic Alloy Buffer Layers

Analytical performance evaluation of AlGaN/GaN metal insulator semiconductor heterostructure field effect transistor and its comparison with conventional HFETs for high power microwave applications

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