Band gap manipulation in diamond-structure semiconductors using shear strain

Diamond-structure semiconductors such as silicon and germanium are among the most studied materials and of tremendous relevance for applications, so understanding their behavior is crucial from both fundamental and technological points of views. Recent ab initio calculations predict that shear strain applied along specific crystallographic directions leads to a strong gap reduction and possible metallization in these materials [1,2]. Here we present an experimental study of shear-induced changes in the band gap of several representative materials. In order to control the stress with high precision, we use a custom-designed pneumatic strain cell that allows us to fine-tune the amount of stress applied to the material and enables a detailed study of how stress along different directions impacts the electronic properties. The results are in good agreement with theoretical predictions and offer a new way to manipulate the fundamental properties of semiconductors.