Dopant-defect interactions and their impact on local crystal stoichiometry studies in Mg-doped GaN via atom probe tomography

TL;DR

This study uses atom probe tomography to analyze dopant-defect interactions in Mg-doped GaN, revealing Mg-rich clusters, dislocation segregation, and impurity effects that influence local stoichiometry and self-compensation mechanisms.

Contribution

It provides detailed 3D visualization of dopant-defect interactions and introduces methods to assess APT data quality in GaN materials.

Findings

Mg-rich clusters and dislocations segregate Mg in GaN.

Impurities like oxygen and hydrogen are adjacent to Mg-rich dislocations.

Local stoichiometry variations are influenced by microfeatures, not artifacts.

Abstract

In this work, doping-defect interactions relevant to self-compensation in p-type GaN were investigated using atom probe tomography. The 3D visualization of ion distribution revealed the formation of spherical Mg-rich clusters and the segregation of Mg dopant towards dislocations in MOCVD-grown GaN:Mg. Impurities related to self-compensation, such as oxygen and hydrogen, were identified and detected adjacent to Mg-rich dislocations. Crystal stoichiometry around the defect regions was investigated to understand how the defects can serve as traps and influence dopant diffusion. Non-stoichiometric regions of N:Ga were found adjacent to Mg-rich dislocations and overlapping with some Mg-rich clusters, indicating potential traps. Variations in N:Ga were not proportional to the Mg content, suggesting that the microfeatures (clusters and dislocations) interact differently with local chemistry. Techniques for defining the quality of an APT experiment through invalidation of artifacts are also demonstrated. Mg-rich defects and variations in N:Ga were found to be independent of artifacts related to the evaporation field in APT.