Low resistive Au-free, Ta-based, recessed ohmic contacts to InAlN/AlN/GaN heterostructures
Journal article, 2015

The formation of recess etched Au-free ohmic contacts to an InAlN/AlN/GaN heterostructure is investigated. A Ta/Al/Ta metal stack is used to produce contacts with contact resistance (R-c) as low as 0.14 Omega mm. It is found that R-c decreases with increasing recess depth until the InAlN barrier is completely removed. For even deeper recesses R-c remains low but requires annealing at higher temperatures for contact formation. The lowest R-c is found for contacts where the recess etch has stopped just above the 2D electron gas channel. At this depth the contacts are also found to be less sensitive to other process parameters, such as anneal duration and temperature. An optimum bottom Ta layer thickness of 5-10 nm is found. Two reliability experiments preliminary confirm the stability of the recessed contacts.

ohmic contact

recess etch


high electron mobility transistor




Johan Bergsten

Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics

Anna Malmros

Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics

M. Tordjman

Thales Group

P. Gamarra

Thales Group

C. Lacam

Thales Group

M. A. di Forte-Poisson

Thales Group

Niklas Rorsman

Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics

Semiconductor Science and Technology

0268-1242 (ISSN) 1361-6641 (eISSN)

Vol. 30 10 105034- 105034

Subject Categories

Electrical Engineering, Electronic Engineering, Information Engineering



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