Atom probe tomography and transmission electron microscopy of a Mg-doped AlGaN/GaN superlattice

The electronic characteristics of semiconductor-based devices are greatly affected by the local dopant atom distribution. In Mg-doped GaN, the clustering of dopants at structural defects has been widely reported, and can significantly affect p-type conductivity. We have studied a Mg-doped AlGaN/GaN superlattice using transmission electron microscopy (TEM) and atom probe tomography (APT). Pyramidal inversion domains were observed in the TEM and the compositional variations of the dopant atoms associated with those defects have been studied using APT. Rarely has APT been used to assess the compositional variations present due to structural defects in semiconductors. Here, TEM and APT are used in a complementary fashion, and the strengths and weaknesses of the two techniques are compared.

Research Highlights
► Mg-rich regions of approximately 5 nm in size were revealed in Mg-doped AlGaN/GaN superlattices using atom probe tomography (APT).
► Transmission electron microscopy (TEM) of the superlattice sample showed pyramidal inversion domains, concluded to be the same Mg-rich features observed by APT.
► The information gained from both the 3D APT study and the 2D TEM characterisation was then compared to determine the strengths and weaknesses of each technique in analysing nanoscale features in nitride materials.