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

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.