Figure 6.

The three-dimensional [3-D] AFM images of the surface morphology. The 3-D AFM images of the surface morphology with various ohmic contact systems after annealing at 850°C for 30 s: (a) sample 1, Ti/Al/Ti/Au with an RMS value of 41.223 nm; (b) sample 2, Ti/Al/Ni/Au with an RMS value of 27.84 nm; (c) sample 3, Ti/Al/Ta/Au with an RMS value of 19.014 nm; and (d) sample 4, the optimized Ti/Al/Ta/Au with a RMS value of 10.006 nm. The images are 3-D AFM of 10 × 10-μm areas.