Composition Metrology of Ternary Semiconductor Alloys Analyzed by Atom Probe Tomography

Abstract

Ternary semiconductor alloys based on the AyB1–yC stoichiometry are widely employed in electronic devices, and their composition plays a key role in band gap engineering of heterostructures. We have studied the crucial issue of accuracy in composition measurements of AlyGa1–yN and MgyZn1–yO alloys using atom probe tomography (APT). The results indicate a similar behavior for both nitride and oxide systems. A correct site fraction y is measured at low field conditions, while Ga and Zn preferentially evaporate at high field, yielding an overestimation of y. Furthermore, APT data sets exhibit local biases depending on the distribution of the electrostatic field at the specimen surface. We estimate the detection efficiencies for each species and interpret the results through a model describing preferential evaporation in simple terms.