Excitonic fine structure of epitaxial Cd(Se,Te) on ZnTe type-II quantum dots

The structure of the ground state exciton Cd(Se,Te) quantum dots embedded in ZnTe matrix is studied experimentally using photoluminescence spectroscopy and theoretically ${\bf k}\cdot{\bf p}$ configuration interaction methods. experiments reveal a considerable reduction fine-structure splitting energy with increase Se content dots. That effect interpreted by theoretical calculations to originate due transition from spatially direct (type-I) indirect (type-II) between electrons holes dot induced Se. trends predicted theory match those experimental results very well.The identifies that main mechanism causing elevated particular type-I multipole expansion exchange interaction. Moreover, reveals for contents $>0.3$, there exist also {\bf peculiar type confinement showing signatures both type~I type~II} which exhibits extraordinary properties, such as almost purely light hole character toroidal shape states.