Dopant-defect interactions in Mg-doped GaN via atom probe tomography

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.

Field‐dependent abundances of hydride molecular ions in atom probe tomography of III‐N semiconductors

“…In the last two decades, laser-assisted atom probe tomography (APT) has proved to be an efficient technique for mapping chemical species in semiconductors. Among its main achievements in microscopy of semiconductors, one could cite the elucidation of the alloy and doping distribution in III-N materials, [1][2][3][4][5] the quantitative definition of interfaces in heterostructures, 6 or the assessment of impurity segregation at defects. 7,8 However, it should not be forgotten that, despite the information of APT is visualised and analysed in a 3D virtual space, this technique is based on the surface phenomenon of field evaporation.…”

Atomic Diffusion of Indium through Threading Dislocations in InGaN Quantum Wells

“…Atom probe tomography (APT) has a high spatial resolution (on the subnanometer scale) and a relatively low detection limit, making it an ideal technique for the evaluation of the local distribution of trace elements near crystal defects such as dislocations and V-pits. − In contrast, (S-)­TEM are suitable for providing crystal information; that is, the analysis of the Burgers vector of dislocations, as well as for obtaining details of the structure of the core. The aim of this study was to accurately determine the structure and elemental distribution around the TDs penetrating InGaN/GaN multiple quantum wells (MQWs) by a correlation analysis using TEM and APT.…”

“…As shown in Figure g, the indium concentration distributed near the dislocation in the GaN layer decreases as the distance from the InGaN layer increases: this phenomenon is regarded as resulting from the diffusion of indium atoms from the InGaN layer. Crucially, the diffusion coefficients of the elements present along the dislocation are orders of magnitude larger than those in the defect-free bulk region, and this type of dislocation-induced diffusion has been observed in several materials, including metals such as Al and semiconductors such as InGaAs and Ge. , This is known as “pipe diffusion”, and the observed diffusion of elements could be related to this phenomenon. Generally, the driving force for diffusion is a concentration gradient.…”