High-transconductance GaN MODFETs

Aktaş, Özgür; Kim, W.; Fan, Z.; Stengel, Franck; Botchkarev, A.; Salvador, A.; Sverdlov, B.; Mohammad, S. Noor; Morkoç̌, H.

doi:10.1109/iedm.1995.497215

Cited by 15 publications

(12 citation statements)

References 3 publications

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“…1- 4 The challenge of growing high quality and defect-free GaN and its alloys, In 1Ϫx Ga x N and Al 1Ϫx Ga x N, is still formidable due to the lack of lattice matched substrates. Most of the previous work has been devoted to the growth of GaN on Al 2 O 3 by metal organometallic vapor pressure epitaxy ͑MOVPE͒ 2,3 or molecular beam epitaxy ͑MBE͒.…”

confidence: 99%

“…4 Successful MBE and MOVPE growth of wurtzitic GaN has been demonstrated on various substrates such as 6H-SiC, 6 MgAl 2 O 4 , 7 Si͑111͒, 8 GaAs, 9 and ZnO͑0001͒. 10,11 Sverdlov et al 6 discussed the possible causes of the dense network of threading defects in epitaxial hexagonal GaN films grown on nonisomorphic substrates and have suggested that the stacking mismatch between the substrate and the epitaxial layer is responsible for many of these defects.…”

confidence: 99%

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Optical properties of GaN grown on ZnO by reactive molecular beam epitaxy

Hamdani

Botchkarev

Kim

et al. 1997

Applied Physics Letters

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108

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High quality wurtzite GaN epilayers have been grown on ZnO(0001) substrates by reactive molecular beam epitaxy. Photoluminescence and reflectivity measurements point to high quality presumably due to the near match of both the crystal lattice parameter and the stacking order between GaN and ZnO. In addition, the good films lack the characteristic yellow photoluminescence band. Any misorientation of the GaN epilayer planes with respect to the ZnO substrate is not detectable with polarized reflectivity. The x-ray double crystal diffraction measurements indicate this misorientation is much smaller than those for GaN epilayers on SiC and Al2O3 .

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confidence: 99%

Optical properties of GaN grown on ZnO by reactive molecular beam epitaxy

Hamdani

Botchkarev

Kim

et al. 1997

Applied Physics Letters

Self Cite

108

View full text Add to dashboard Cite

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“…[1][2][3][4][5] Sapphire remains the current substrate of choice for the growth of GaN thin films despite a large ͑12.6%͒ lattice mismatch. However, the growth of thin AlN 6,7 or GaN 8 layers at lower temperatures prior to depositing the GaN active layer has been found to improve significantly the heterostructure in terms of both structural and optoelectronic properties, promoting lateral growth of the epilayer.…”

Section: Introductionmentioning

confidence: 99%

In situ transmission electron microscopy of AlN growth by nitridation of (0001) α-Al2O3

Yeadon

Marshall

Hamdani

et al. 1998

Journal of Applied Physics

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“…[1][2][3][4] Ohmic-contact resistances should be reduced as low as possible to obtain high-efficiency performance of devices. [5][6][7][8][9][10] For GaN electronic and optical devices, Lin et al first reported the Ti/ Al metal scheme. 5 Fan et al obtained a 10 −7 ⍀ cm 2 level of contact resistivity with the Ti/ Al/ Ni/ Au metal scheme.…”

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confidence: 99%

Investigation of Ta∕Ti∕Al∕Ni∕Au ohmic contact to AlGaN∕GaN heterostructure field-effect transistor

Kim

Jeon

et al. 2005

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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An AlGaN / GaN wide band-gap semiconductor with the Ta/ Ti/ Al/ Ni/ Au ohmic contact ͑7.5 ϫ 10 −7 ⍀ cm 2 ͒ was demonstrated by 700°C annealing for 1 min. High-resolution electron microscopy and synchrotron-radiation x-ray diffraction showed that nitride phases were formed at the interface between the metal and the AlGaN layer. The thick formation of TaN / TiN interfacial layers appears to be responsible for the good ohmic contact behavior in Ta/ Ti/ Al/ Ni/ Au metal scheme. The surface morphology of Ta-based contacts is superior to that of the Ti/ Al/ Ni/ Au metal scheme. The fabricated heterostructure field-effect transistor exhibited the saturation drain current density of 605 mA/ mm and transconductance of 246 mS/ mm.The GaN wide band-gap semiconductors have desirable material properties including a large band gap, low value of the dielectric constant, high thermal conductivity, and high critical-electric field for breakdown. Especially, the AlGaN / GaN heterostructure has been demonstrated to produce a two-dimensional electron gas ͑2DEG͒ that has high sheet-charge density on the order of 10 13 cm −2 , excellent saturation velocity of about 2 ϫ 10 7 V / cm, and roomtemperature mobility in the range of 1000-1500 cm 2 /V s. These make possible attracting devices for high-temperature, high-frequency, and high-power applications. [1][2][3][4] Ohmic-contact resistances should be reduced as low as possible to obtain high-efficiency performance of devices. 5-10 For GaN electronic and optical devices, Lin et al. first reported the Ti/ Al metal scheme. 5 Fan et al. obtained a 10 −7 ⍀ cm 2 level of contact resistivity with the Ti/ Al/ Ni/ Au metal scheme. 6 Ti/ Al metallization with hightemperature annealing ͑Ͼ800°C͒ has also been used as the standard ohmic contact on AlGaN / GaN heterostructure field-effect transistors ͑HFETs͒ in order to achieve low contact resistivity ͑Ͻ10 −5 ⍀ cm 2 ͒. 8-10 Liu et al. first reported that the Ti/ Al metal scheme on AlGaN / GaN showed contact resistivity of 3.2ϫ 10 −6 ⍀ cm 2 with 950°C heat treatment. 11 Qiao et al. recently reported that the addition of a Ta layer below the Ti/ Al metal layer leads to contact resistivity as low 5 ϫ 10 −7 ⍀ cm 2 at the 950°C annealing temperature. 12,13 Because high-temperature annealing has some drawbacks, such as surface roughness, it is necessary to develop new methods which reduce contact resistivity at moderate annealing temperatures. Many attempts have been made to find a way of lowering the contact resistivity and improving the surface characteristics. Recent results have shown that the additional layers on the Ti/ Al metal scheme ͑Ni/ Au, Pt/ Au, and Ti/ Au͒ reduce the contact resistivity at moderate-temperature annealing. The reported contact resistivity is 2.8ϫ 10 −6 ⍀ cm 2 with 700°C heat treatment for Ti/ Al/ Ni/ Au, 5.3ϫ 10 −6 ⍀ cm 2 with 800°C heat treatment for Ti/ Al/ Ti/ Au, and 4.7ϫ 10 −7 ⍀ cm 2 with 850°C heat treatment for Ti/ Al/ Mo/ Au. [14][15][16][17] The tunneling effect due to nitride formation at the AlGaN interface is genera...

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High-transconductance GaN MODFETs

Cited by 15 publications

References 3 publications

Optical properties of GaN grown on ZnO by reactive molecular beam epitaxy

Optical properties of GaN grown on ZnO by reactive molecular beam epitaxy

In situ transmission electron microscopy of AlN growth by nitridation of (0001) α-Al2O3

Investigation of Ta∕Ti∕Al∕Ni∕Au ohmic contact to AlGaN∕GaN heterostructure field-effect transistor

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