The resistance of Ti/Al-based contacts to N-face GaN/AlGaN heterostructures was found to depend sensitively on their interfacial composition. Limiting the thickness of the first layer deposited (either Al or Ti) to a few nanometers resulted in low contact resistances after annealing for 1min at 500°C. The lowest contact resistance of 0.10 Ω mm (contact resistivity of 3×10-7 Ω cm2) was achieved with 3nm of Al as the first deposited layer. Transmission electron microscopy revealed a thin Ti-Al-Ga-N layer adjacent to the GaN in this annealed Al/Ti/Al contact, while the contact resistance was higher when the interfacial layer contained only Ti, Ga, and N. The simultaneous presence of Al and Ti next to GaN at the onset of reaction was found to be critical for achieving the lowest contact resistance.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)