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

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., C_2V, C_S, C₁), while it has no effect on the FSS and polarization anisotropy in high symmetry QDs (e.g., C_3V, D_2d). 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.