Optical anisotropy and the direction of polarization of exciton emissions in a semiconductor quantum dot: Effect of heavy- and light-hole mixing

Abstract

The dependence of the directions of polarization of exciton emissions, fine structure splittings (FSS), and polarization anisotropy on the light- and heavy-hole (LH–HH) mixing in semiconductor quantum dots (QDs) is investigated using a mesoscopic model. In general, all QDs have a four-fold exciton ground state. Two exciton states have directions of polarization in the growth-plane, while the other two are along the growth direction of the QD. The LH–HH mixing does affect the FSS and polarization anisotropy of bright exciton states in the growth-plane in the low symmetry QDs (e.g., C2V, CS, C1), while it has no effect on the FSS and polarization anisotropy in high symmetry QDs (e.g., C3V, D2d). When the hole ground state is pure HH or LH, the bright exciton states in the growth-plane are normal to each other. The LH–HH mixing affects the relative intensities and directions of bright exciton states in the growth-plane of the QD. The polarization anisotropy of exciton emissions in the growth-plane of the QD is independent of the phase angle of LH–HH mixing but strongly depends on the magnitude of LH–HH mixing in low symmetry QDs.