Anisotropic exchange splitting of excitons in (001)GaAs/Al0.3Ga0.7As superlattice studied by reflectance difference spectroscopy

Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, People’s Republic of China
Journal of Applied Physics (Impact Factor: 2.18). 08/2008; 104(1):013106 - 013106-6. DOI: 10.1063/1.2947602
Source: IEEE Xplore


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 [110] 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 [110] 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.

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    ABSTRACT: The off-diagonal element of the Luttinger Hamiltonian responsible for the coupling of heavy hole–light hole states has been calculated for symmetric/asymmetric semiconductor quantum dots. It has been found that the splitting arising due to finite off-diagonal elements of the Luttinger Hamiltonian and the size asymmetry of the quantum dot is counterbalanced. The numerical estimates made for CdSe/ZnSe quantum dot manifest minimal energy splitting when the size asymmetry parameter is around 0.3.
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