Annealing temperature dependence of Ohmic contact resistance and morphology on InAlN/GaN high electron mobility transistor structures

Ti/Al/Ni/Au Ohmic contact metallization on InAlN/GaN heterostructures both with and without a thin GaN cap layer was annealed at different temperatures. The minimum transfer resistance for the contacts of 0.65   Ω     mm (specific contact resistivity of 2 × 10 − 5   Ω   cm 2 ) was achieved after 800...

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Bibliographic Details
Published in:Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena Microelectronics and nanometer structures processing, measurement and phenomena, 2011-03, Vol.29 (2)
Main Authors: Lo, C.-F., Liu, L., Chang, C. Y., Ren, F., Craciun, V., Pearton, S. J., Heo, Y. W., Laboutin, O., Johnson, J. W.
Format: Article
Language:English
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Summary:Ti/Al/Ni/Au Ohmic contact metallization on InAlN/GaN heterostructures both with and without a thin GaN cap layer was annealed at different temperatures. The minimum transfer resistance for the contacts of 0.65   Ω     mm (specific contact resistivity of 2 × 10 − 5   Ω   cm 2 ) was achieved after 800   ° C annealing for structures without the GaN cap, while those with the cap exhibited their lowest resistance at higher temperatures. The contact morphology showed considerable roughening by 750   ° C but the carrier mobility was stable until annealing temperatures of 850   ° C . Diffuse scattering experiments showed that the morphological roughness of the InAlN/GaN interface increased as a result of annealing at these temperatures and the data were consistent with outdiffusion of Ga into the InAlN. Unpassivated high electron mobility transistors with a gate dimension of 0.7 × 180   μ m 2 were fabricated using these contacts and showed a maximum drain current of 1.3 A/mm and an extrinsic transconductance of 366 mS/mm. The presence of the GaN cap increased the effective barrier height of Ni/Au Schottky contacts from 0.91 to 1.01 eV on the heterostructure.
ISSN:1071-1023
2166-2746
1520-8567
2166-2754
DOI:10.1116/1.3545811