Hillocks, Pits, and Etch Rate in Germanium Crystals

Symmetric faceted etch hillocks have been observed on certain germanium surface orientations exposed to an H2O2–HF (Superoxol) etchant. Considerations of surface curvature and etch rate lead to the conclusion that the faces bounding the hillocks must be at saddle points on an etch rate vs orientation surface. A measurement of etch rate throughout the stereographic triangle has supported this conclusion. The formation of dislocation pits and hillocks is discussed in terms of the variation of surface etch rate with orientation.