Sample preparation of GaN-based materials on a sapphire substrate for STEM analysis.

In this work, a detailed TEM sample preparation recipe based on a wedge polishing technique for GaN-based materials is presented. The obtained samples have atomically flat surfaces without any obvious surface damages such as the formation of amorphous layers. A composition estimation of Al(x)Ga(1-x)N from Z-contrast STEM imaging is carried out using these samples. The results are in good accord with the nominal composition.