Bad sapphire substrate, 3-D

The quality of single crystal substrates can be critical for good crystal growth. In this case, sapphire substrates are used for the growth of GaN which is used in blue-light laser applications. The adjacent gallery image gives an example of a good substrate, which has a uniform surface texture that is relatively flat. In this image we see a bad substrate which has a rather large population of point defects that protrude from the surface and make the growth of GaN difficult. The Quesant SPM does a good job of characterizing these samples, using WaveMode.