Ohmic Contacts on N-Face n-Type GaN After Low Temperature Annealing

L. Redaelli1, A. Muhin1,2, S. Einfeldt1, P. Wolter1, L. Weixelbaum1, and M. Kneissl1,3

Published in:

IEEE Photonics Technol. Lett., vol. 25, no. 13, pp. 1278-1281 (2013).

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The electrical properties of different metal systems for ohmic contacts on the nitrogen-face of c-plane n-type GaN substrates are investigated. The metal contacts are compatible with the fabrication process and the packaging technology for group III-nitride laser diodes. The metal system Ti/Al/Mo/Ti/Ni/Au/Ti/Pt is determined as the best suitable, since it is ohmic already after annealing at a temperature of 450 °C for 60 s. This annealing temperature is high enough to make the contact insensitive against later soldering on a heat-sink at 330 °C. At the same time, the temperature is low enough that the Pd-based p-contact, previously annealed at 530 °C, does not degrade. In addition, the Ti/W/Al and Pd/Ti/Al metal systems form low-resistance ohmic contacts, too, although they require a longer annealing time of several minutes or a higher temperature of 500 °C.

1 Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, D-12489 Berlin, Germany
2 Technische Universität Ilmenau, 98693 Ilmenau, Germany
3 Institute for Solid State Physics, Technische Universität Berlin, 10623 Berlin, Germany

Index Terms:

GaN laser diodes, contacts to n-GaN, N-face GaN, GaN wet-chemical etching, TMAH.