Low resistance ohmic contacts to n-GaN and n-AlGaN using NiAl

Abstract

The intermetallic compound NiAl (50:50 at. %) has been shown to be a low-resistance ohmic contact to n-GaN and n-AlGaN. NiAl contacts on n-GaN (n = 2.5 × 1017 cm-3) had a specific contact resistance of 9.4 × 10-6 Ω cm2 upon annealing at 850°C for 5 min. NiAl contacts annealed at 900°C for 5 min in n-Al0.12Ga0.88N (n = 2.4 × 1018 cm-3) and n-Al0.18Ga0.82N (n = 2.7 × 1018 cm-3) had specific contact resistances of 2.1 × 10-5 Ω cm2 and 4.7 × 10-5 Ω cm2, respectively. Additionally, these contacts were subjected to long-term annealing at 600°C for 100 h. On n-GaN, the contact specific contact resistance degraded from 9.4 × 10-6 Ω cm2 to 5.3 × 10-5 Ω cm2 after the long-term anneal. Contacts to n-Al0.18Ga0.82N showed only slight degradation with a change in contact resistance, from 4.7 × 10-5 Ω cm2 to 9.2 × 10-5 Ω cm2. These results demonstrate the NiAl has great promise as a stable, low-resistance contact, particularly to n-AlGaN used in high-temperature applications. © 2000 American Institute of Physics.