Morphological and electrical comparison of Ti and Ta based ohmic contacts for AlGaN/GaN-on-SiC HFETs
Journal article, 2017

The morphology and impact on leakage currents of two different ohmic metal stacks for GaN based transistor devices is investigated in this work. The results have implications for the performance and reliability of a GaN transistor device. A low temperature Ta based and a higher temperature anneal Ti based metallization are compared. The low temperature process shows a smoother metal semiconductor interface together with several orders of magnitude lower vertical and lateral leakage compared to the conventional higher temperature process. In addition to the leakage tests, back bias ramping experiments are performed unveiling potential advantages of the conventional approach in mitigating current collapse. However the low leakage will enable higher voltage operation making the low temperature process the preferable choice for high power RF applications, if simultaneously current collapse can be controlled.

Ohmic contact


Current collapse

Leakage current




A. Pooth

IQE (Europe) Ltd.

University of Bristol

Johan Bergsten

Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics

Niklas Rorsman

Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics

H. Hirshy

Cardiff University

R. Perks

Cardiff University

Paul J. Tasker

Cardiff University

T. Martin

IQE (Europe) Ltd.

R. F. Webster

University of Bristol

D. Cherns

University of Bristol

M. J. Uren

University of Bristol

M. Kuball

University of Bristol

Microelectronics and Reliability

0026-2714 (ISSN)

Vol. 68 2-4

Subject Categories

Electrical Engineering, Electronic Engineering, Information Engineering



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9/6/2018 7