Characterization of tantalum-silicon films on GaAs at elevated temperatures

RF sputter-deposited tantalum-silicon films on GaAs have been investigated using four-point probe, glancing-angle X-ray diffraction, Auger electron spectroscopy, and MeV
⁴
He
⁺
backscattering spectrometry as a function of annealing up to 850°C. Experimental results show that: 1) there is no observable Ta or Si migration from the TaSi
2
overlayer into the GaAs substrate; 2) the structure of the As-sputtered film is amorphous and crystallization into a polycrystalline TaSi
2
layer occurs at ∼ 500°C accompanied by a reduction in electrical resistivity. After annealing at 650°C, As and/or Ga appear to have migrated into the TaSi
2
layer. The amount of this migration remains unchanged up to an annealing temperature of 850°C. On the other hand, migration of Ta and/or Si into the GaAs substrate is not detected up to 850°C. This absence of the Ta and/or Si migration contributes to the stability of the Schottky-diode characteristics against annealing reported previously.