Journal
APPLIED PHYSICS LETTERS
Volume 107, Issue 26, Pages -Publisher
AMER INST PHYSICS
DOI: 10.1063/1.4939190
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Funding
- National Natural Science Foundation of China [61474138, 61404163, 61306102, 61274090]
- National Science and Technology Major Project through the Ministry of Science and Technology of China [2014ZX01002101-007]
- opening project of Key Laboratory of Microelectronics Devices and Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences
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The physical mechanism of low-thermal-budget Au-free ohmic contacts to AlGaN/GaN hetero-structures is systematically investigated with current-voltage, high-resolution transmission electron microscopy, and temperature-dependent contact resistivity characterizations. With a low annealing temperature of 600 degrees C, pre-ohmic recess etching of the AlGaN barrier down to several nanometers is demonstrated to be an effective method to reduce the contact resistance between Ti/Al/Ti/W ohmic metals and AlGaN/GaN heterostructures. However, further over recess of the AlGaN barrier leads to only sidewall contact to 2D electron gas channel and thus degraded contact performance. It is verified by temperature-dependent contact resistivity measurements that field emission (tunneling) dominates the current transport mechanism in Au-free ohmic contacts with AlGaN barrier partially and over recessed, while both field emission and thermionic emission contribute to traditional Ti/Al/Ni/Au ohmic contacts to AlGaN/GaN heterostructures that annealed at high temperature (850 degrees C). (C) 2015 AIP Publishing LLC.
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