Tuning the Optoelectronic Properties of Capped Tensile-strained Ge Quantum Dots by Lattice Mismatch

Abstract

The optoelectronic properties of capped tensile-strained Ge quantum dot (QD) was studied with different lattice mismatch, which was formed by Ge and various substrate. The strain distribution of Ge QDs were simulated with the aid of finite element method (FEM) and the electronic structures of capped tensile-strained Ge QDs under such strain was calculated via deformation potential theory and effective mass approach (EMA). The size effect of Ge QDs was also considered. It was found that the capped QDs hold larger strain than the uncapped ones. In addition, the energy difference between Γ and L conduction valley reduced with the increase of the QD size and the lattice mismatch, thus converting the Ge QDs into the direct band gap material. The energy of the direct band gap decreased with the increase of the QDs' size. This work shows that the tensile-strained Ge QD is a promising light emission material for future optoelectronic applications such as lasers on Si.