Anisotropy of optical transitions in (110)-oriented quantum wells

The in-plane anisotropy of interband optical transitions is theoretically investigated for GaAs/${\mathrm{Al}}_{0.3}$ ${\mathrm{Ga}}_{0.7}$As and GaAs/AlAs (110)-oriented quantum-well films. This calculation takes into account the multiplicity of the valence band including the split-off state. The anisotropy analysis reveals that the well-width variation induces an exchange of heavy-hole-like or light-hole-like attributes between the two excited subband states in the valence band. The anisotropy is enhanced to a remarkable degree by narrowing the well, especially in GaAs/AlAs. This theory also clarifies that the pronounced well-width dependence of anisotropy is caused by the presence of the split-off state.