Bound biexciton luminescence in nitrogen δ-doped GaAs



We have studied the detailed fine structure splitting of the photoluminescence lines exhibiting the superlinear excitation power dependence in nitrogen δ-doped GaAs. The symmetric splitting energy observed between the 1.493 and 1.509 eV lines suggests that these two lines originate from the same impurity center because the mixing of the bright- and dark-exciton components depends on the electron-hole exchange energy and the local-strain field. The excitation power dependence of these two lines indicates that the 1.509 eV line is attributed to the biexciton luminescence corresponding to the 1.493 eV line.