Mechanism of Ti/Al/Ti/W Au-free ohmic contacts to AlGaN/GaN heterostructures via pre-ohmic recess etching and low temperature annealing
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China)
- Key Laboratory of Microelectronics Devices and Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China)
The physical mechanism of low-thermal-budget Au-free ohmic contacts to AlGaN/GaN heterostructures is systematically investigated with current-voltage, high-resolution transmission electron microscopy, and temperature-dependent contact resistivity characterizations. With a low annealing temperature of 600 °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 °C)
- OSTI ID:
- 22486308
- Journal Information:
- Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 26 Vol. 107; ISSN APPLAB; ISSN 0003-6951
- Country of Publication:
- United States
- Language:
- English
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