Molten barium hydroxide as defect selective drop etchant for dislocation analysis on aluminum nitride layers

In this article, the suitability of the etchants NaOH/KOH and Ba(OH)${}_2$ for defect etching of metalorganic vapour-phase epitaxy (MOVPE) grown AlN layers with a MgO-assisted "drop method" is compared. Defect selectivity for the new etchant Ba(OH)${}_2$ is confirmed by the local TEM analysis. Temperature dependence (420-500 °C) of etch pit sizes of a-, mixed-, and c-type dislocations for both etchants are investigated by statistical evaluation of scanning electron microscopy (SEM) images. Additionally, the etch pit shape is analyzed for samples etched at 460 °C by atomic force microscopy (AFM) measurements. While a- and mixed-type dislocations result in pits of comparable size and shape for both etchants, c-type dislocations are already strongly etched with NaOH/KOH at low temperatures leading to over-etching and MgO precipitation. Ba(OH)${}_2$, in contrast, generates smaller c-type etch pits at low and medium etching temperatures and no MgO precipitates and is therefore preferable for drop etching. (© 2022 The Authors. physica status solidi (a) applications and materials science published by Wiley‐VCH GmbH)