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International Journal of Microwave Science and Technology
Volume 2012 (2012), Article ID 418264, 5 pages
http://dx.doi.org/10.1155/2012/418264
Research Article

Copper-Metalized GaAs pHEMT with Cu/Ge Ohmic Contacts

1Microelectronics Department, Research and Production Company “Micran”, 47 Vershinina Street, Tomsk 634045, Russia
2RF Electronics Department, Submicron Technologies, 8 Akademicheskiy Avenue, Tomsk 634021, Russia

Received 29 November 2010; Accepted 1 March 2011

Academic Editor: Rüdiger Quay

Copyright © 2012 E. V. Anichenko et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The fully Cu-metalized GaAs pHEMT using developed Cu/Ge-based ohmic contacts and T-gate Ti/Mo/Cu with length of the 150 nm has been successfully fabricated for the high-frequency applications. The fabricated Cu-metalized pHEMT has a maximum drain current of 360 mA/mm, an off-state gate-drain breakdown of 7 V, and a transconductance peak of 320 mS/mm at 𝑉 d s = 3  V. The maximum stable gain value was about 15 dB at frequency 10 GHz. The current gain cutoff frequency of the copper-metalized device is about 60 GHz at 𝑉 d s = 3  V, and maximum frequency of oscillations is beyond 100 GHz. This work investigated in detail the formation of Cu/Ge ohmic contacts to n-GaAs with an atomic hydrogen preannealing step. It was shown that after the first preliminary annealing is carried out in a flow of atomic hydrogen with a flow density of atoms of 1 0 1 3 / 1 0 1 6 at. c m 2 s − 1 a reduction in specific contact resistance by 2 / 2 . 5 times is observed. The reduction in specific contact resistance is apparently caused by the action of the hydrogen atoms which minimise the rate of the oxidizing reactions and activate solid phase reactions forming the ohmic contact during the thermal treatment process.