|
1 Department of Materials Science and Engineering,
Pohang University of
Science and Engineering, Pohang, Korea
2 Institute of Physics, Academia Sinica, Nankang,
Taipei 11529, Taiwan,
Republic of China
3 Equipe Structure et Comportement Thermomécanique des Matériaux
(CRISMAT UMR
6508 CNRS), ISMRA 6, Bd Maréchal Juin,
Caen Cedex F-14050, France
| We investigated the nano-structural evolution of metal contacts to GaN during annealing and the correlations between nano-structures and electrical properties for two typical ohmic contacts; Pd as a non-alloyed contact and Ni/Au as an alloyed one. Pd was completely transformed to two kinds of epitaxial Pd gallides, Ga2Pd5 and Ga5Pd, at 700°C. In the alloyed Ni/Au contact, the reaction chemistry was rather complicated. Ni4N formation was found in N2 annealed sample at 500°C of which reaction kinetics was greatly affected by the catalytic effect of Au. The high-temperature compounds were correlated with the rapid degradation of electrical properties during annealing. Meanwhile, the thermal stability of Ni/Au contact greatly improved by suppressing the activated Ni reactivity, which was able to be obtained by forming preferential Ni-O bonding through annealing in air. |
full paper (pdf, 79 Kb)