Low-resistance ohmic contacts on <i>p</i>-type GaN using Ni/Pd/Au metallization

Chu, C. Y. Cyrus; Yu, C. C.; Wang, Y. K.; Tsai, Jang-Zern; Lai, Fang I.; Wang, S. C.

doi:10.1063/1.1327276

Cited by 60 publications

(16 citation statements)

References 17 publications

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“…On the other hand, for p-type GaN, because of the difficulty in achieving high carrier density and the absence of suitable metals with high work function, a high-quality ohmic contact with very low contact resistivity (∼10 −7 Ω · cm 2 ) is still not achieved. For p-type GaN, however, the best result (4.5 × 10 −6 Ω · cm 2 ) could be obtained from the Be-doped (Concentration 8.1 × 10 19 cm −3 ) sample with Ni/Pd/Au contacts [22]. A very recent study showed that ohmic contacts to n-SiC are formed by using a pure Ni-based layer with a thin underlying Si layer.…”

Section: A Terahertz Performance Comparison Of Gan and Sic Impatts: mentioning

confidence: 97%

“…A specific contact resistance of 1.0 × 10 −4 Ω · cm 2 can be achieved in this technique. If a similar metal composition is deposited on the Be-implanted p ++ -type GaN layer with a carrier density of 8.1 × 10 19 cm −3 , without further annealing process, the sample will show good ohmic contact with a contact resistance of 4.5 × 10 −6 Ω · cm 2 [22]. A new metallization scheme has recently been developed for obtaining very low ohmic contact to n-GaN [21].…”

Section: ) Fabrication Issues Related To Gan Impatt Diodementioning

confidence: 99%

“…Using photolithography and liftoff techniques, low-resistance contact metals, an alloy of Ni (20 nm)/Pd (20 nm)/Au (100 nm) [22], can be deposited inside the windows by an electron beam evaporator. The metal contacts should then be annealed in air, nitrogen, and oxygen ambient conditions at different annealing temperatures ranging from 350 • C to 650 • C. The measurement of specific contact resistance may be done by a circular TLM (CTLM) system.…”

Section: ) Fabrication Issues Related To Gan Impatt Diodementioning

confidence: 99%

See 2 more Smart Citations

Photosensitivity Analysis of Gallium Nitride and Silicon Carbide Terahertz IMPATT Oscillators: Comparison of Theoretical Reliability and Study on Experimental Feasibility

Mukherjee¹,

Mazumder

Roy³

2008

IEEE Trans. Device Mater. Relib.

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Reliability of terahertz-frequency (∼1.0 THz) characteristics of wide-bandgap (WBG) wurtzite (Wz)-GaN-and 4H-SiC-based p ++ nn ++ -type single-drift-region (SDR) impact avalanche transit time (IMPATT) devices (normal and photoilluminated) is compared through a simulation scheme. The simulation experiment reveals that an RF power density of 3.37 × 10 11 W · m −2 (efficiency of 18.2%) at around 1.126 THz may be realized from the optimized unilluminated GaN IMPATT device, whereas the unilluminated 4H-SiC IMPATT device is expected to generate an RF power density of 1.35 × 10 11 W · m −2 (efficiency of 9%) at 1.05 THz. However, the parasitic series resistance reduces the maximum exploitable power density from the terahertz devices. Under optical illumination, additional photogenerated carriers are created in the devices, and these carriers change the admittance and negative resistance properties of the terahertz IMPATT diodes. The performance modulation of the terahertz devices is simulated, and the results are compared in this paper. Under external radiation, the operating frequencies of the GaN-and SiC-based diodes are found to shift upward by 6.0 and 40.0 GHz, respectively, with degradation of maximum output-power density level and device negative resistance. The extensive simulation experiments establish that, although the photosensitivity of the 4H-SiC-based IMPATT device is better than its GaN counterpart, the overall terahertz performance of the unilluminated GaN IMPATT device is far better than the 4H-SiC-based device, particularly in terms of output power and efficiency. The simulation results and the proposed experimental methodology presented here can be used for realizing optically tuned WBG IMPATT oscillators for terahertz communication.

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Section: A Terahertz Performance Comparison Of Gan and Sic Impatts: mentioning

confidence: 97%

Section: ) Fabrication Issues Related To Gan Impatt Diodementioning

confidence: 99%

Section: ) Fabrication Issues Related To Gan Impatt Diodementioning

confidence: 99%

See 1 more Smart Citation

Photosensitivity Analysis of Gallium Nitride and Silicon Carbide Terahertz IMPATT Oscillators: Comparison of Theoretical Reliability and Study on Experimental Feasibility

Mukherjee¹,

Mazumder

Roy³

2008

IEEE Trans. Device Mater. Relib.

View full text Add to dashboard Cite

show abstract

“…For p-type GaN, however, the best result (4.5 Â 10 À6 X cm 2 ) could be obtained from Be-doped (conc. 8.1 Â 10 19 cm À3 ) sample with Ni/Pd/Au contacts [19]. It is not worthy to mention that, in order to get appreciable power (Watt level) from a THz source, low specific contact resistance ($10 À7 X cm 2 ) should be achieved, since at THz region intrinsic diode negative resistance is usually very small.…”

Section: Resultsmentioning

confidence: 99%

Wide-Bandgap III–V nitride based avalanche transit-time diode in Terahertz regime: Studies on the effects of punch through on high frequency characteristics and series resistance of the device

Mukherjee¹,

Roy²

2010

Current Applied Physics

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“…A large variety of elemental and multicomponent metallizations have been explored for ohmic contacts to n-GaN and p-GaN. [3][4][5][6][7][8] Additionally, various surface treatment techniques such as wet chemical surface modification, 9 dry etching, 10 and laser etching 11 have been used to reduce the ohmic contact resistance, yet specific contact resistances are still sufficiently high so as to impact device performance, particularly for p-GaN.…”

Section: Introductionmentioning

confidence: 99%

Nanopatterned Contacts to GaN

Kim

Deb

Sands

2007

Journal of Elec Materi

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The effect of nanoscale patterning using a self-organized porous anodic alumina (PAA) mask on the electrical properties of ohmic and Schottky contacts to n-GaN was investigated with the aim of evaluating this approach as a method for reducing the specific contact resistance of ohmic contacts to GaN. The electrical characteristics of contacts to these nanopatterned GaN samples were compared with contacts to planar, chemically prepared (''as-grown'') GaN samples and reactive ion etched (RIE) GaN films without any patterning. The specific contact resistivities to unintentionally doped n-GaN using a Ti/Al bilayer metallization were determined to be 7.4 · 10 )3 W cm 2 for the RIE sample and 7.0 · 10 )4 W cm 2 for the PAA patterned sample. Schottky metal contacts with Pt and Ni were prepared on the three samples to validate the effects of RIE and nanopatterning on electrical behavior. The effective barrier height was decreased and the reverse current was increased significantly in the PAA patterned sample. The radius of curvature of the nanoscale corrugation in the patterned interface was smaller than the depletion width. The reduction of the depletion width at sharp corners enhanced the local tunneling current, reducing the specific contact resistivity and decreasing the effective barrier height. These results suggest that nanopatterning with PAA on GaN can significantly lower the contact resistance.

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Low-resistance ohmic contacts on p-type GaN using Ni/Pd/Au metallization

Cited by 60 publications

References 17 publications

Photosensitivity Analysis of Gallium Nitride and Silicon Carbide Terahertz IMPATT Oscillators: Comparison of Theoretical Reliability and Study on Experimental Feasibility

Photosensitivity Analysis of Gallium Nitride and Silicon Carbide Terahertz IMPATT Oscillators: Comparison of Theoretical Reliability and Study on Experimental Feasibility

Wide-Bandgap III–V nitride based avalanche transit-time diode in Terahertz regime: Studies on the effects of punch through on high frequency characteristics and series resistance of the device

Nanopatterned Contacts to GaN

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