Formation of extended thermal etch pits on annealed Ge wafers

TL;DR

This study investigates the formation of extended, faceted etch pits on annealed germanium wafers at high temperatures, revealing their dependence on thermal conditions and dislocation interactions.

Contribution

It demonstrates that extended etch pits form on Ge wafers due to preferential desorption near dislocation pile-ups during high-temperature annealing.

Findings

Pits form at T > 750°C during thermal cycles.

Pits' morphology matches that of dislocation etching.

Distribution of pits indicates dislocation interactions.

Abstract

An extended formation of faceted pit-like defects on Ge(001) and Ge(111) wafers was obtained by thermal cycles to T> 750 {\deg}C. This temperature range is relevant in many surface-preparation recipes of the Ge surface. The density of the defects depends on the temperature reached, the number of annealing cycles performed and correlates to the surface-energy stability of the specific crystal orientation. We propose that the pits were formed by preferential desorption from the strained regions around dislocation pile-ups. Indeed, the morphology of the pits was the same as that observed for preferential chemical etching of dislocations while the spatial distribution of the pits was clearly non-Poissonian in line with mutual interactions between the core dislocations.