METALLURGY OF AL-NI-GE OHMIC CONTACT FORMATION ON N-GAAS

Al-Ni-Ge ohmic contacts on n-GaAs were prepared by sequential vapor de position and furnace annealing at 500 degrees C. The metallurgical pro perties of the contacts were studied by transmission electron microsco py. It was found that while Al-Ni-Ge as a whole is relatively stable a gainst GaAs, extensive interfacial reactions readily occur within the contact layers, resulting in a very stable layered structure of the ty pe Al3Ni/Ni-Ge/GaAs, with epsilon'-Ni5Ge3 being the major phase in the Ni-Ge layer. GaAs twins and Ni-As precipitates were found in a thin l ayer immediately below the metallization, suggesting that the ohmic be havior can be accounted for in terms of a GaAs regrowth mechanism. (C) 1995 American Vacuum Society.