Impact of layer structure on performance of unpassivated AlGaN∕GaN∕SiC HEMTs

Bernát, J.; Wolter, M.; Fox, A.; Marso, Michel; Flynn, J. S.; Brandes, George R.; Kordoš, P.

doi:10.1049/el:20040021

Cited by 20 publications

(12 citation statements)

References 6 publications

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“…dc and rf results of the HEMT devices are presented elsewhere. 8 Room temperature Hall effect measurements on the van der Pauw patterns ͑Table I͒ show the expected dependence on the carrier supply doping level. The sheet carrier density n Hall increases with increasing doping level while the mobility Hall is reduced.…”

Section: Institut Für Schichten Und Grenzflächen (Isg) and Cni-centermentioning

confidence: 87%

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Influence of a carrier supply layer on carrier density and drift mobility of AlGaN/GaN/SiC high-electron-mobility transistors

Marso

Bernát

Javorka

et al. 2004

Applied Physics Letters

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Sheet carrier concentration and low-field drift mobility of intentionally undoped and modulation-doped AlGaN/GaN heterostructures on SiC substrate were evaluated by capacitance-voltage and channel conductivity measurements. Sheet carrier concentration and average mobility at 0 V gate bias correspond to standard Hall results. Sheet carrier density increases from 6.8×1012 cm−2 for the undoped sample up to 1×1013 cm−2 for the device with the highest doping concentration, while the mobility decreases from 1800 to 1620 cm2/V s. The local mobility, on the other hand, depends only on the actual sheet carrier density and is not influenced by the doping concentration of the carrier supply layer. It reaches a maximum value of 2100 cm2/V s at a carrier density of 3×1012 cm−2.

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Section: Institut Für Schichten Und Grenzflächen (Isg) and Cni-centermentioning

confidence: 87%

“…On the other hand, this result supports our previous observation of better overall AlGaN/GaN HEMT performance using doped structure in comparison to undoped one. 8 …”

Section: Institut Für Schichten Und Grenzflächen (Isg) and Cni-centermentioning

confidence: 99%

Influence of a carrier supply layer on carrier density and drift mobility of AlGaN/GaN/SiC high-electron-mobility transistors

Marso

Bernát

Javorka

et al. 2004

Applied Physics Letters

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“…The larger drain saturation current at the doped devices increases the power performance at low frequencies, e.g. at 2 GHz [3]. In this work we investigate the influence of a carrier supply layer on the small signal RF performance of MOCVD grown AlGaN/GaN HEMTs on SiC substrate.…”

Section: Introductionmentioning

confidence: 99%

Influence of carrier supply doping on the RF properties of AlGaN/GaN/SiC high‐electron‐mobility transistors

Marso¹,

Bernát²,

Javorka³

et al. 2005

phys. stat. sol. (c)

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We have fabricated undoped as well as modulation-doped AlGaN/GaN HEMTs on SiC substrate. The influence of the carrier supply layer on device performance is investigated by Hall, channel conductivity, small signal RF and delay time evaluation. While the doping layer improves the DC performance it degrades the RF behaviour of the device with the highest carrier supply doping of 5x10 18 cm -3. The channel conductivity measurements show identical dependence of the mobility on carrier concentration for all samples. The saturation velocity, extracted by evaluation of the total delay time as function of the inverse drain current, decreases from 0.86x10 7 cm/s for the undoped device to 0.7x10 7 cm/s for the highest doped HEMT. This result shows that the degradation of RF performance is due to the reduction of the effective saturation velocity caused by the carrier supply layer.

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“…The intentionally undoped structure consists of a 40 nm thick AlN nucleation layer, 3 µm GaN buffer, followed by a 30 nm Al 0.28 GaN barrier layer. Room temperature Hall measurements yield a 2DEG carrier concentration of 7.1x10 12 cm -2 and a mobility of 1835 cm 2 /V s. The devices are prepared using the standard HEMT fabrication process (for details see [7]). No mesa etching is performed to avoid a parasitic photocurrent created in the unshielded buffer between the contact pads.…”

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confidence: 99%

An AlGaN/GaN two‐color photodetector based on an AlGaN/GaN/SiC HEMT layer structure

Marso

Fox

Heidelberger

et al. 2006

Phys. Status Solidi (c)

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The optoelectronic properties of MSM diodes that are based on an AlGaN/GaN HEMT layer system are investigated as function of the applied bias. For low voltages, the two-dimensional electron gas acts as a barrier for the depletion layer. Therefore, only the upper AlGaN barrier layer contributes to the photocurrent. In the high voltage regime the depletion region penetrates the GaN buffer that adds the spectral responsivity of GaN to the pure AlGaN behaviour in the low voltage regime. The ratio of the responsivities at 350 nm and 300 nm wavelength can be switched from 0.01 at 2.5 V to 0.8 at 4 V bias. This property makes the MSM-2DEG a candidate for use as two-color photodetector. Device fabrication uses standard HEMT processing steps, allowing integration in HEMT circuits without the need of sophisticated growth or etching techniques. 1 Introduction In the last years, GaN based transistors have shown their potential for high power and temperature applications. However, layer growth and device fabrication technology are not yet mature to integrate devices with different layer systems on the same substrate. Therefore, the monolithic integration of components with different functionalities is limited to devices using the same layer structure. In this work we investigate a metal-semiconductor-metal diode that is based on a HEMT layer structure (MSM-2DEG, Fig. 1). Fabrication of the MSM-2DEG diode consists of standard HEMT fabrication steps (mesa etching, Schottky electrode and contact pad fabrication), allowing easy integration in HEMT circuits. The MSM-2DEG device has been analyzed extensively for use as varactor diode and as photodetector [1][2][3][4]. In this work we investigate the bias dependence of the spectral responsivity of the AlGaN/GaN MSM-2DEG photodetector.

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Impact of layer structure on performance of unpassivated AlGaN∕GaN∕SiC HEMTs

Cited by 20 publications

References 6 publications

Influence of a carrier supply layer on carrier density and drift mobility of AlGaN/GaN/SiC high-electron-mobility transistors

Influence of a carrier supply layer on carrier density and drift mobility of AlGaN/GaN/SiC high-electron-mobility transistors

Influence of carrier supply doping on the RF properties of AlGaN/GaN/SiC high‐electron‐mobility transistors

An AlGaN/GaN two‐color photodetector based on an AlGaN/GaN/SiC HEMT layer structure

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