The emergence of new materials have paved the way to nano-electronic and optoelectronic devices with improved or new capabilities. For instance, III-V based alloys have revolutionized the LED industry finding applications in high power electronics, and may speed up micro- electronic devices in the near future. Unfortunately, their wide scaled implementation is still limited by the presence of highly concentrated crystallographic or impurity defects. Such defects are typically of sub-nanometric size and are therefore difficult to observe directly. Defect metrology is by consequence of very high importance to assess fabrication processes. Three methods are traditionally implemented to determine the density of defects in optoelectronic devices