This paper deals with the outstanding electrical and structural proper
ties of Ru-based Schottky and ohmic contacts fabricated by electron be
am evaporation on n- and p+-type GaAs, respectively. The effective and
flatband barrier heights were evaluated by standard current-voltage (
I-V)(T) and capacitance-voltage (C-V T) measurements, over the tempera
ture (T) range 100 to 350 K. The modified Richardson constant, A*, va
ried between 2.2 and 4.9 A cm-2 K-2, depending upon the annealing temp
erature. AES depth profiles indicated that Ru forms structurally very
stable contacts to GaAs, with no evidence from XPS measurements of any
compound formation between Ru and GaAs even after annealing up to 500
-degrees-C. A sharp increase was observed in the formation of Ga2O3 at
the interface between the Ru layer and the GaAs after vacuum annealin
gs at temperatures of 450-degrees-C and above. Only limited diffusion
of arsenic through the Ru layer was observed after annealing at 400-de
grees-C, but increased rapidly above 450-degrees-C. A Au/Ru/p+-GaAs oh
mic contact system showed comparable specific contact resistance (5.5
x 10(-6) OMEGA.cm2) to those systems commonly used, but with superior
surface morphology.