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

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 x 10(17) cm(-3)) had a specific contact resistance of 9.4 x 10(-6) Ohm cm(2) upon annealing at 850 degrees C for 5 min. NiAl contacts annealed at 900 degrees C for 5 min in n-Al0.12Ga0.88N (n = 2.4 x 10(18) cm(-3)) and n-Al0.18Ga0.82N (n = 2.7 x 10(18) cm(-3)) had specific contact resistances of 2.1 x 10(-5) Ohm cm(2) and 4.7 x 10(-5) Ohm cm(2), respectively. Additionally, these contacts were subjected to long-term annealing at 600 degrees C for 100 h. On n-GaN, the contact specific contact resistance degraded from 9.4x10(-6) Ohm cm(2) to 5.3 x 10(-5) Ohm cm(2) after the long-term anneal. Contacts to n-Al0.18Ga0.82N showed only slight degradation with a change in contact resistance, from 4.7 x 10(-5) Ohm cm(2) to 9.2 x 10(-5) Ohm cm(2). These results demonstrate the NiAl has great promise as a stable, low-resistance contact, particularly to n-AlGaN used in high-temperature applications. (C) 2000 American Institute of Physics. [S0003-6951(00)02329-9].