A Study of Low-Annealing-Temperature Ohmic Contact on n-Type GaN Layers

Shyh-Chiang Shen, Georgia Institute of Technology
Minkyu Cho, Georgia Tech
Marzieh Bakhtiary Noodeh, Georgia Tech
Theeradetch Detchprohm, Georgia Tech
Russell Dupuis, Georgia Tech
Barry Wu, Keysight Technologies, Inc.
Don D’Avanzo, Keysight Technologies, Inc.

Typical n-type ohmic contact formation for GaN material systems requires high-temperature thermal processes. The high-temperature process often leads to a rough surface after the annealing step. Low-annealing-ohmic contact is advantageous to prevent undesired surface roughening on the metal stack during this thermal process.  We report an approach to achieve low contact resistance on n-type GaN layers using a nitrogen plasma and a conventional Ti/Al-based metal stacks.  We observed an as-deposit ohmic contact behavior on the n-type contact with a specific contact resistance (rc,sp) in the mid-E-6 Ω∙cm2 range.  The rc,sp was further reduced to  6.8E-7 Ω∙cm2 after an annealing step at 600 oC.

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