Anisotropic exchange splitting of excitons in (001)GaAs/Al0.3Ga0.7As superlattice studied by reflectance difference spectroscopy
ABSTRACT Anisotropic exchange splitting (AES) is induced by the joint effects of the electron-hole exchange interaction and the symmetry reduction in quantum wells and quantum dots. A model has been developed to quantitatively obtain the electron-hole exchange energy and the hole-mixing energy of quantum wells and superlattices. In this model, the AES and the degree of polarization can both be obtained from the reflectance difference spectroscopy. Thus the electron-hole exchange energy and the hole-mixing energy can be completely separated and quantitatively deduced. By using this model, a (001)5 nm GaAs /7 nm Al 0.3 Ga 0.7 As superlattice sample subjected to  uniaxial strains has been investigated in detail. The n=1 heavy-hole (1H1E) exciton can be analyzed by this model. We find that the AES of quantum wells can be linearly tuned by the  uniaxial strains. The small uniaxial strains can only influence the hole-mixing interaction of quantum wells, but have almost no contribution to the electron-hole exchange interaction.