Origin of improved RF performance of AlGaN/GaN MOSHFETs compared to HFETs

Marso, Michel; Heidelberger, G.; Indlekofer, K. M.; Bernát, J.; Fox, A.; Kordoš, P.; Lüth, H.

doi:10.1109/ted.2006.875819

Cited by 81 publications

(62 citation statements)

References 33 publications

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“…2 for HFET and 9 nm oxide MOSHFET, were found. This is in contradiction to reported observation that the peak drift mobility in AlGaN/GaN MOSHFET with SiO 2 gate oxide is higher than that of HFET due to the screening of the Coulomb interactions of the charged surface and interface states by electrostatic induction in the gate metallization of the MOSHFET [14].…”

Section: Methodscontrasting

confidence: 99%

Characterization of AlGaN/GaN MOSHFETs with Al₂O₃ as gate oxide

Gregušová

Stoklas

Ćičo

et al. 2007

Phys. Status Solidi (c)

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PACS 73.40. Qv, 85.30.Tv We report on AlGaN/GaN metal-oxide-semiconductor heterostructure field-effect transistors (MOSHFETs) with MOCVD deposited Al 2 O 3 as a gate oxide. Properties of MOSHFETs with 9 nm and 14 nm thick Al 2 O 3 are compared with conventional HFETs prepared simultaneously on the same layer structure. Lower gate leakage current (~10 −5 A/mm at −10 V) and higher saturated drain current (up to 40 %) are obtained for MOSHFETs than those for HFETs. In contradiction to previously reported data, the extrinsic transconductance for MOSHFETs is also higher (up to 37% of peak values) than that for HFET. This indicates on semi-conductive rather than insulating properties of Al 2 O 3 gate oxide. Pulsed I−V measurements (pulse width 1 µs) yielded lower but still measurable current collapse in MOSHFETs compared to HFETs. Nevertheless, obtained results show that Al 2 O 3 gate oxide, after optimising its microstructure and thickness, can be preferable for the preparation of AlGaN/GaN MOSHFETs. 1 Introduction The GaN-based heterostructure field-effect transistors (HFETs) offer superior characteristics in terms of high-frequency output power, breakdown field and operating temperature when compared with GaAs-based HFETs. Recently, there is a growing interest in exploring AlGaN/GaN metal-oxide-semiconductor HFETs (MOSHFETs) because of lower gate leakage currents as well as possible application of high positive gate voltages thereby increasing voltage swing. In the first studies on AlGaN/GaN MOSHFETs, SiO 2 [1] and SiN [2, 3] were chosen as a good candidate for the gate dielectric applications. SiN was originally proposed as the passivation layer of AlGaN/GaN HFETs, i.e. to reduce their current collapse, and a density of interface states about ten times lower than that for SiO 2 was found [4]. However, the current collapse problem is not mitigated sufficiently using these two types of a gate dielectric [5]. This is the main reason that another, novel type, dielectrics such as AlN, MgO, Al 2 O 3 , ZrO, Sc 2 O 3 , Ga 2 O 3 , HfO 2 , Gd 2 O 3 are under study [6---9], and references therein]. However, the preference of a gate dielectric type has not been defined yet. Moreover, significantly better device performance was recently observed if a semi-conducting layer was used instead of highly insulating one [10]. Thin layer of Al 2 O 3 might fulfil well requirements on a gate material for GaN-based devices. The dielectric constant of Al 2 O 3 is larger than that of SiN and SiO 2 , ε = 8−10, its breakdown filed is high, E br > 10 MV/cm, and Al 2 O 3 can be prepared in different crystalline forms by various deposition techniques. Oxidation of thin MBE grown Al layer [11], sputtering [12] and plasma enhanced atomic layer deposition [13] were used to prepare AlGaN/GaN MOSHFETs with Al 2 O 3 as a gate oxide. Unfortunately, current collapse evaluation and large-signal rf measurements are not reported yet.

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Section: Methodscontrasting

confidence: 99%

Characterization of AlGaN/GaN MOSHFETs with Al₂O₃ as gate oxide

Gregušová

Stoklas

Ćičo

et al. 2007

Phys. Status Solidi (c)

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“…While keeping the merits of conventional Schottky-gate-based HFETs, i.e., a high density of two-dimensional electron gas ͑2DEG͒ at the AlGaN/GaN interface, high cutoff and maximum frequencies, and the thermal and chemical stability of AlGaN and GaN, MISHFETs offer many advantages over HFETs, such as lower gate leakage current, higher breakdown voltage, better thermal stability of the gate, mitigation of current collapse, a wider range of gate voltage sweep, and higher maximum drain current and output power. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] These features are crucial for applications in high-power, high-temperature electronics, 7,17 particularly to realize low on-resistance and normally off highpower FETs. 15,18 Although the standard high frequency capacitancevoltage ͑C-V͒ measurement at room temperature ͑RT͒ is usually done on metal/insulator/semiconductor heterostructure ͑MISH͒ capacitors and/or metal/semiconductor heterostructure ͑MSH͒ Schottky diodes before the fabrication and characterization of the MISHFET devices, the C-V data are often used only to estimate the thicknesses of the insulator film and/or the AlGaN layer 1,4,12,16,19 or to calculate the 2DEG density.…”

Section: Introductionmentioning

confidence: 99%

Effects of interface states and temperature on the C-V behavior of metal/insulator/AlGaN/GaN heterostructure capacitors

Miczek

Mizue

Hashizume

et al. 2008

Journal of Applied Physics

179

141

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The impact of states at the insulator/AlGaN interface on the capacitance-voltage ͑C-V͒ characteristics of a metal/insulator/AlGaN/GaN heterostructure ͑MISH͒ capacitor was examined using a numerical solver of a Poisson equation and taking into account the electron emission rate from the interface states. A parallel shift of the theoretical C-V curves, instead of the typical change in their slope, was found for a MISH device with a 25-nm-thick AlGaN layer when the SiN x / AlGaN interface state density D it ͑E͒ was increased. We attribute this behavior to the position of the Fermi level at the SiN x / AlGaN interface below the AlGaN valence band maximum when the gate bias is near the threshold voltage and to the insensitivity of the deep interface traps to the gate voltage due to a low emission rate. A typical stretch out of the theoretical C-V curve was obtained only for a MISH structure with a very thin AlGaN layer at 300°C. We analyzed the experimental C-V characteristics from a SiN x / Al 2 O 3 / AlGaN/ GaN structure measured at room temperature and 300°C, and extracted a part of D it ͑E͒. The relatively low D it ͑ϳ10 11 eV −1 cm −2 ͒ in the upper bandgap indicates that the SiN x / Al 2 O 3 bilayer is applicable as a gate insulator and as an AlGaN surface passivant in high-temperature, high-power AlGaN/GaN-based devices.

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“…GaN/AlGaN heterojunction field effect transistors (HFET's) have been demonstrated for high power, high frequency applications and are being actively commercialized. High gate leakage due to the Schottky gate on HFET devices has led to investigation of metal oxide semiconductor heterojunction field effect transistors (MOSHFETs, MOS-HFETs, MISHFETs) which have been shown to decrease gate leakage [1] and for some dielectrics increase transconductance [2,3]. Numerous gate dielectrics have been evaluated for these purposes including PECVD SiO 2 [4], Si 3 N 4 [4], Al 2 O 3 [5], AlON [6], Ga 2 O 3 [7], HfO 2 [8], Sc 2 O 3 [9], and Zr 2 O 3 [10].…”

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confidence: 99%

“…Numerous gate dielectrics have been evaluated for these purposes including PECVD SiO 2 [4], Si 3 N 4 [4], Al 2 O 3 [5], AlON [6], Ga 2 O 3 [7], HfO 2 [8], Sc 2 O 3 [9], and Zr 2 O 3 [10]. Threshold voltage for HFET and MOSHFET devices is typically less than zero [2][3][4][5][6][7][8][9][10] resulting in devices which are normally on. For power semiconductor applications, it is strongly desirable to have enhancement mode devices for safety and simplified circuit design.…”

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confidence: 99%

Performance improvement of AlGaN/GaN high electron mobility transistors with atomic layer deposition (ALD) of SiO₂ and HfAlO dielectrics

Kirkpatrick

Lee

Yang

et al. 2011

Phys. Status Solidi C

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GaN metal oxide semiconductor heterojunction field effect transistors have been fabricated with SiO2 and HfAlO gate dielectrics deposited via atomic layer deposition. These transistors have threshold voltages more positive than ‐4 V and exhibit 3 orders of magnitude lower gate leakage than Schottky gated heterojunction field effect transistors (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Origin of improved RF performance of AlGaN/GaN MOSHFETs compared to HFETs

Cited by 81 publications

References 33 publications

Characterization of AlGaN/GaN MOSHFETs with Al₂O₃ as gate oxide

Characterization of AlGaN/GaN MOSHFETs with Al₂O₃ as gate oxide

Effects of interface states and temperature on the C-V behavior of metal/insulator/AlGaN/GaN heterostructure capacitors

Performance improvement of AlGaN/GaN high electron mobility transistors with atomic layer deposition (ALD) of SiO₂ and HfAlO dielectrics

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Origin of improved RF performance of AlGaN/GaN MOSHFETs compared to HFETs

Cited by 81 publications

References 33 publications

Characterization of AlGaN/GaN MOSHFETs with Al2O3 as gate oxide

Characterization of AlGaN/GaN MOSHFETs with Al2O3 as gate oxide

Effects of interface states and temperature on the C-V behavior of metal/insulator/AlGaN/GaN heterostructure capacitors

Performance improvement of AlGaN/GaN high electron mobility transistors with atomic layer deposition (ALD) of SiO2 and HfAlO dielectrics

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Characterization of AlGaN/GaN MOSHFETs with Al₂O₃ as gate oxide

Characterization of AlGaN/GaN MOSHFETs with Al₂O₃ as gate oxide

Performance improvement of AlGaN/GaN high electron mobility transistors with atomic layer deposition (ALD) of SiO₂ and HfAlO dielectrics