With scaling of semiconductor devices showing no signs of abating and three-dimensional structures now being developed, new metrologies to meet these demands are being sought. Atom probe tomography offers the potential to meet these challenges, and here, the authors present an in-depth study focused on finding useable conditions for accurate stoichiometric analysis of GaN and AlGaN. By varying the laser energy/power, changes in the average tip field were induced, and the resulting impact on the measured stoichiometry was investigated. A strong variation in the GaN stoichiometry as a function of the average tip field was found, although a range of conditions that enable accurate stoichiometry were determined. Moreover, the stoichiometric variation as a function of tip field was highly reproducible across instruments and laser wavelengths. However, for AlGaN, the N concentration was always underestimated. To try and establish the underlying cause of the N underestimation, potential loss mechanisms which include N2 sublimation, N2 neutral generation from molecular ion dissociation, and differences in the field of evaporation between the matrix elements and multihits were considered and are reported herein.

No abstract

No abstract