Special Issue Paper

Journal of Electronic Materials

, Volume 32, Issue 5, pp 335-340

First online:

Long-term thermal stability of Ti/Al/Mo/Au ohmic contacts on n-GaN

  • D. SelvanathanAffiliated withDepartment of Electrical and Computer Engineering and Micro and Nanotechnology Laboratory, University of Illinois at Urbana Champaign
  • , L. ZhouAffiliated withDepartment of Electrical and Computer Engineering and Micro and Nanotechnology Laboratory, University of Illinois at Urbana Champaign
  • , V. KumarAffiliated withDepartment of Electrical and Computer Engineering and Micro and Nanotechnology Laboratory, University of Illinois at Urbana Champaign
  • , I. AdesidaAffiliated withDepartment of Electrical and Computer Engineering and Micro and Nanotechnology Laboratory, University of Illinois at Urbana Champaign
  • , N. FinneganAffiliated withMaterials Research Laboratory, University of Illinois at Urbana Champaign

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Abstract

Improved performance of the ohmic contacts on n-GaN has been demonstrated with the use of MoAu as the capping layer on TiAl metallization. Contact resistance as low as 0.13 Θ-mm was achieved in these ohmic contacts when annealed at 850°C for 30 sec. We have studied the long-term thermal stability of these contacts at 500°C, 600°C, 750°C, and 850°C, respectively. The Ti/Al/Mo/Au metallization forms low contact-resistance ohmic contacts on n-GaN that are stable at 500°C and 600°C after 25 h of thermal treatment. The ohmic-contact performance degrades after 10 h of thermal treatment at 750°C, while the contacts exhibit nonlinear current-voltage (I-V) characteristics after 1 h of thermal treatment at 850°C with the formation of oxide on the surface of the contacts accompanied by surface discoloration. The intermetallic reactions taking place in the contacts during the long-term thermal treatments were studied using Auger electron spectroscopy (AES), and the surface morphology was characterized using atomic force microscopy (AFM).

Key words

Thermal stability ohmic contacts Ti/Al/Mo/Au GaN