RF Power Measurements of InAlN/GaN Unstrained HEMTs on SiC Substrates at 10 GHz

Jessen, Gregg H.; Gillespie, J.; Via, G. D.; Crespo, A.; Langley, Derrick; Aumer, M. E.; Ward, Chris; Henry, H.G.; Thomson, D. B.; Partlow, Deborah P.

doi:10.1109/led.2007.895417

Cited by 29 publications

(10 citation statements)

References 13 publications

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“…Traditionally, Ti/Al/X/Au ohmic metallization scheme was widely used in InAlN/GaN HEMTs, where X could be Ni, Mo, Ti, etc., [5][6][7][8][9][10] and it acted as a diffusion barrier layer to the Au cap layer. These Ti/Al based contacts usually need high annealing temperature (>800 C) to achieve a low contact resistance.…”

Section: Introductionmentioning

confidence: 99%

Low thermal budget Hf/Al/Ta ohmic contacts for InAlN/GaN-on-Si HEMTs with enhanced breakdown voltage

Liu¹,

Singh²,

Ngoo³

et al. 2014

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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Articles you may be interested inTi/Al/Ti/Ni/Au ohmic contacts on AlGaN/GaN high electron mobility transistors with improved surface morphology and low contact resistanceThe authors have studied the electrical characteristics of Hf/Al/Ta ohmic contacts on In 0.18 Al 0.82 N/GaN heterostructure grown on Si (111) substrate. With annealing at 600 C in vacuum (which is $200 C lower than that for traditional Ti/Al/Ni/Au contacts), a minimum ohmic contact resistance of $0.58 XÁmm and specific contact resistivity of $6.75 Â 10 À6 XÁcm 2 are obtained. The minimum contact resistance of Hf/Al/Ta contacts is comparable to that of Ti/Al/Ni/Au contacts. Owing to the lower annealing temperature, Hf/Al/Ta contacts exhibit better surface morphology and edge acuity. More importantly, Hf/Al/Ta contacts show a smooth interface with In 0.18 Al 0.82 N/GaN, whereas spike structures that penetrate the In 0.18 Al 0.82 N layer are observed for Ti/Al/Ni/Au contacts. As a result, the source-carrier-injection induced breakdown mechanism is reduced in the In 0.18 Al 0.82 N/GaN-on-Si high electron mobility transistors (HEMTs) with Hf/Al/Ta ohmic contacts, thereby leading to an improved three-terminal off-state breakdown voltage by about 100 V ($53.5% improvement), in comparison to Ti/Al/Ni/Au based HEMTs.

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Section: Introductionmentioning

confidence: 99%

Low thermal budget Hf/Al/Ta ohmic contacts for InAlN/GaN-on-Si HEMTs with enhanced breakdown voltage

Liu¹,

Singh²,

Ngoo³

et al. 2014

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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“…and a Au capping layer. [4][5][6][7][8][9][10][11] In order to realize a low contact resistivity for the aforementioned ohmic contact scheme, the metal stack is usually annealed at high temperature (∼800…”

mentioning

confidence: 99%

Mechanisms of Ohmic Contact Formation and Carrier Transport of Low Temperature Annealed Hf/Al/Ta on In_0.18Al_0.82N/GaN-on-Si

Liu

Singh

Kyaw

et al. 2014

ECS J. Solid State Sci. Technol.

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The mechanisms of ohmic contact formation and carrier transport of low temperature (600 GaN based high mobility electron transistors (HEMTs) are of interest for applications in high-temperature, high-speed and high-power devices owing to the wide bandgap, high saturation velocity and high critical breakdown field of GaN.1,2 To realize high performance in AlGaN/GaN and InAlN/GaN HEMTs, good ohmic contacts with low resistivity are critical. Although very low contact resistance can be achieved by means of regrowth technique, 3 alloyed ohmic contacts are still most widely used due to their fabrication simplicity and low cost. The typical ohmic metal stacks are Ti/Al based (e.g., Ti/Al/X/Au), where Ti is the bottom layer, followed by Al, a diffusion barrier layer X (where X = Ni, Mo and Ti, etc.) and a Au capping layer. [4][5][6][7][8][9][10][11] In order to realize a low contact resistivity for the aforementioned ohmic contact scheme, the metal stack is usually annealed at high temperature (∼800• C), which leads to the presence of randomly distributed TiN inclusions, so-called contact inclusions or contact spikes, formed at the metal-semiconductor interface. 8,12 The presence of contact inclusions has shown to be vital to achieving good ohmic properties by Kim et al. 13 for InAlN/GaN HEMTs, as contact inclusions provide direct electron transport paths through the InAlN barrier layer to the 2DEG channel. On the other hand, these contact inclusions can also lead to lower breakdown voltage for GaN based HEMTs. 14,15 In our recent study, 16 we have proposed a low thermal budget (≤600• C) Hf/Al/Ta ohmic contact scheme on unintentionally doped In 0.18 Al 0.82 N/GaN grown on Si substrate, which has demonstrated low contact resistivity, smooth surface morphology and metalsemiconductor interface. In addition, the In 0.18 Al 0.82 N/GaN HEMTs fabricated with Hf/Al/Ta ohmic contacts have shown significantly improved breakdown voltage, compared to devices with traditional Ti/Al/Ni/Au ohmic contacts, owing to the source-carrier-injection mechanism suppressed by the smooth metal-semiconductor interface in the former. Our low thermal budget Hf/Al/Ta ohmic contacts show that even with the absence of contact inclusions, good ohmic contact properties can be achieved. This is in contrast to the result of Kim et al., which has shown the necessity of contact inclusions to ohmic contact formation. We noted that our InAlN layer is much thinner than that of Kim et al., hence may not need the presence of contact inclusions for good ohmic contact formation. In addition, it is noted that although analytically studies on the transport mecha- * Electrochemical Society Active Member.z E-mail: a0068100@nus.edu.sg; elecef@nus.edu.sg nism of ohmic contacts with spike structures on AlGaN/GaN 17,18 and InAlN/GaN 13,19 heterostructures have been reported, similar studies for ohmic contacts with a smooth metal-semiconductor interface on InAlN/GaN have not been reported. Hence, the Hf/Al/Ta contacts can be used to understand the carrier transport mechani...

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“…Despite this, with the inclusion of an AlN spacer layer to improve the 2DEG mobility, 5,20 respectable performances have been demonstrated. 21,22,23 In this manuscript, we report on the effect of the barrier layer composition on the gate lag suffered by these devices and find that the lag increases as the layers move further from lattice matching. Additionally, we find that though the gate lag is not attributable to the amount of gate leakage, it is correlated to the rate of change of the gate leakage current, suggesting that as gate leakage paths open up as bias is changing, traps that are responsible for gate lag become activated and can contribute to the lag.…”

Section: Introductionmentioning

confidence: 94%

Measurements of gate lag in high-quality nearly lattice matched InAlN/AlN/GaN HFET structures

Leach

et al. 2010

SPIE Proceedings

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The promise of InAlN-based HFET devices stems from the relatively large band and spontaneous polarization discontinuities and at the interface and the lack of misfit strain when grown lattice matched to GaN. However, there still exists some question as to what the true lattice matching condition of InAlN to GaN is due to discrepancies in the literature values of lattice parameters of the InN binary, and of the InAlN bowing parameters. We used the gate lag measurement as a supplementary technique to verify lattice matching to the underlying GaN, as we expect the strain in layers one source of lag, associated with piezoelectric charge at the surface. We observe very low lag for nearly lattice matched barrier and barriers under tensile strain, and a marked increase as the composition deviates from the lattice matched condition toward compressively strained layers. Additionally, FETs fabricated on a nearly lattice matched InAlN layer boasted a maximum drain current of over 1.5A/mm and ~2.0A/mm and transconductances of ~275mS/mm and ~300mS/mm at DC and in pulsed modes, respectively, and a cutoff frequency of 15.9GHz (an f T *L G product of 10.3) for a gate length of 0.65μm.

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RF Power Measurements of InAlN/GaN Unstrained HEMTs on SiC Substrates at 10 GHz

Cited by 29 publications

References 13 publications

Low thermal budget Hf/Al/Ta ohmic contacts for InAlN/GaN-on-Si HEMTs with enhanced breakdown voltage

Low thermal budget Hf/Al/Ta ohmic contacts for InAlN/GaN-on-Si HEMTs with enhanced breakdown voltage

Mechanisms of Ohmic Contact Formation and Carrier Transport of Low Temperature Annealed Hf/Al/Ta on In_0.18Al_0.82N/GaN-on-Si

Measurements of gate lag in high-quality nearly lattice matched InAlN/AlN/GaN HFET structures

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RF Power Measurements of InAlN/GaN Unstrained HEMTs on SiC Substrates at 10 GHz

Cited by 29 publications

References 13 publications

Low thermal budget Hf/Al/Ta ohmic contacts for InAlN/GaN-on-Si HEMTs with enhanced breakdown voltage

Low thermal budget Hf/Al/Ta ohmic contacts for InAlN/GaN-on-Si HEMTs with enhanced breakdown voltage

Mechanisms of Ohmic Contact Formation and Carrier Transport of Low Temperature Annealed Hf/Al/Ta on In0.18Al0.82N/GaN-on-Si

Measurements of gate lag in high-quality nearly lattice matched InAlN/AlN/GaN HFET structures

Contact Info

Product

Resources

About

Mechanisms of Ohmic Contact Formation and Carrier Transport of Low Temperature Annealed Hf/Al/Ta on In_0.18Al_0.82N/GaN-on-Si