Figure 5.

The SEM photographs of the surface morphology. The SEM photographs of the surface morphology with various ohmic contact systems after annealing at 850°C for 30 s: (a) sample 1, Ti/Al/Ti/Au; (b) sample 2, Ti/Al/Ni/Au; (c) sample 3, Ti/Al/Ta/Au; and (d) sample 4, the optimized Ti/Al/Ta/Au. The images show the metal on either side of a 5-μm gap.