We report on a study of Al and Ti/Al contacts to n-type GaN. Al contacts on n-GaN (7 × 1017 cm-3) annealed in forming gas at 600°C reached a minimum contact resistivity of 8 × 10-6 Ω cm2 and had much better thermal stability than reported by previous researchers. Ti/Al (35/115 nm) contacts on n-GaN (5 × 1017 cm-3) had resistivities of 7 × 10-6 and 5 × 10-6 Ω cm2 after annealing in Ar at 400°C for 5 min and 600°C for 15 s, respectively. Depth profiles of Ti/Al contacts annealed at 400°C showed that low contact resistance was only achieved after Al diffused to the GaN interface. We propose that the mechanism for Ohmic contact formation in Ti/Al contacts annealed in the 400-600°C range includes Ti reducing the GaN native oxide and an Al-Ti intermetallic coming into intimate contact with the GaN.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)