Low resistance ohmic contact to n-GaN with a separate layer method

Wu, Yifeng; Jiang, Wei; Keller, B.P.; Keller, S.; Kapolnek, D.; DenBaars, Steven P.; Mishra, Umesh K.; Wilson, B.L.H.

doi:10.1016/s0038-1101(96)00151-7

Cited by 50 publications

(31 citation statements)

References 7 publications

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“…The specific contact resistance was as low as ϳ7.7ϫ10 Ϫ6 ⍀ cm 2 , which is compatible with the previously reported value on n-GaN. 9 The self-aligned device differs from a conventional device in that n-GaN regions were selectively regrown adjacent to the gate electrode, effectively reducing parasitic resistances and eliminating the extension of gate depletion region. However, the compromise that one makes in such a self-aligned device is a reduced gate-drain breakdown voltage.…”

Section: ͓S0003-6951͑98͒03047-2͔supporting

confidence: 89%

High-transconductance self-aligned AlGaN/GaN modulation-doped field-effect transistors with regrown ohmic contacts

Chen

Keller

Parish

et al. 1998

Applied Physics Letters

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Self-aligned AlGaN/GaN modulation-doped field-effect transistors (MODFETs) with high transconductances have been demonstrated on a sapphire substrate. Source and drain were selectively regrown with ∼1700 Å of n-GaN adjacent to the gate electrode. Source resistance was reduced to 0.95 Ω mm from 1.4 to 1.8 Ω mm with conventional GaN-based MODFETs. These self-aligned devices show a record high value of extrinsic transconductance ∼400 mS/mm for AlGaN/GaN MODFETs with a gate length of 1.2 μm.

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Section: ͓S0003-6951͑98͒03047-2͔supporting

confidence: 89%

High-transconductance self-aligned AlGaN/GaN modulation-doped field-effect transistors with regrown ohmic contacts

Chen

Keller

Parish

et al. 1998

Applied Physics Letters

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“…When necessary, Al or Au layers were deposited on top of the contacts after processing to reduce the contact metal sheet resistance to permit an accurate determination of the actual contact resistivity. A similar procedure has been used by Wu et al 8 for Ti contacts to n-GaN. Auger electron spectroscopy depth profiles were performed using a Kratos Analytical XSAM 800 pci.…”

Section: Methodsmentioning

confidence: 99%

Study of contact resistivity, mechanical integrity, and thermal stability of Ti/Al and Ta/Al ohmic contacts to n-type GaN

Luther

Mohney

DeLucca

et al. 1998

Journal of Elec Materi

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“…The temperatures where ohmic contact behavior was observed for vacuum annealing are comparable to the tempera- tures requried to form ohmic contacts by halogen lamp rapid thermal annealing. 7,8,15 The variation of the specific contact resistivity as a function of operating temperature is shown in Fig. 5 for the Cr/ Al/Ni/Au contacts on n-GaN (1.1ϫ10 18 cm Ϫ3 ) vacuum annealed at 950°C for 2 min, where the optimum values of c were achieved for this metallization system.…”

Section: B Vacuum Annealingmentioning

confidence: 99%

“…Aluminum, with the work function of 4.08 eV, which is close to the electron affinity of GaN ͑4.1 eV͒, is an excellent candidate for forming ohmic contacts to n-type GaN. There are several reports [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] on ohmic contacts to n-GaN with varying results. Of all the metal systems proposed, the Ti/Al bilayer metal system is presently the most widely used.…”

Section: Introductionmentioning

confidence: 99%

Cr/Al and Cr/Al/Ni/Au ohmic contacts to n-type GaN

Papanicolaou

Edwards

Rao

et al. 2000

Journal of Applied Physics

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Disorder induced semiconductor to metal transition and modifications of grain boundaries in nanocrystalline zinc oxide thin film J. Appl. Phys. 112, 073101 (2012) Control of normal and abnormal bipolar resistive switching by interface junction on In/Nb:SrTiO3 interface Appl. Phys. Lett. 101, 133506 (2012) Cross-plane electronic and thermal transport properties of p-type La0.67Sr0.33MnO3/LaMnO3 perovskite oxide metal/semiconductor superlattices J. Appl. Phys. 112, 063714 (2012) Polarization Coulomb field scattering in In0.18Al0.82N/AlN/GaN heterostructure field-effect transistorsIn this work we investigate the performance of Cr/Al and Cr/Al/Ni/Au ohmic contacts on n-type GaN. Annealing of the contacts was achieved by using a low temperature conventional quartz tube furnace in an Ar ambient and a new vacuum annealing technique using a tungsten strip heater. Low specific contact resistivity ( c ) metallizations were achieved with furnace annealing at considerably lower temperatures ͑550-600°C͒ than those typically required for GaN contacts by halogen lamp rapid thermal annealing ͑ϳ900°C͒. Vacuum annealing was found to require temperatures similar to those used in halogen lamp rapid thermal annealing for forming ohmic contacts on n-type GaN, but with minimal oxidation of the Al surface. For the Cr/Al bilayer on GaN with n doping of 10 18 cm Ϫ3 , minimum specific contact resistivities of 1.6ϫ10 Ϫ4 ⍀ cm 2 and 2.3ϫ10 Ϫ5 ⍀cm 2 were achieved for furnace annealing and vacuum annealing, respectively. Our experiments showed that, when Cr was used as a contact material, the simultaneous presence of Cr and Al was necessary in order to obtain the best possible ohmic properties. Furthermore, the Cr/Al contacts maintained good stability at elevated temperatures. The Cr/Al/Ni/Au system offers lower c values and even greater temperature stability than the Cr/Al system when annealed in the 800-1200°C temperature range. Atomic force microscopy investigations indicated that the introduction of the Ni/Au overlayer had the effect of increasing the surface roughness after annealing.

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Low resistance ohmic contact to n-GaN with a separate layer method

Cited by 50 publications

References 7 publications

High-transconductance self-aligned AlGaN/GaN modulation-doped field-effect transistors with regrown ohmic contacts

High-transconductance self-aligned AlGaN/GaN modulation-doped field-effect transistors with regrown ohmic contacts

Study of contact resistivity, mechanical integrity, and thermal stability of Ti/Al and Ta/Al ohmic contacts to n-type GaN

Cr/Al and Cr/Al/Ni/Au ohmic contacts to n-type GaN

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