Luminescence and Excitation Spectra of Exciton Emission in GaAs

Luminescence, excitation, and photoconductivity spectra of epitaxial n‐ and p‐type GaAs at 1.6 K are measured with high resolution, using very low intensity of excitation. Under this condition, it is found that the (D°, X) bound exciton emission is split into two components, and that further structure is observable between the (D°, X) and the luminescence band, recently attributed to lower branch polariton emission. In particular, two very sharp lines are seen ≈ 0.5 meV above the (D°, X) emission. These lines are observed in all our samples, and their intensities seem to be related to the strength of the (D°, X) line. Analysis of the excitation spectra lead to the identification of three emission lines. These are the n = 2 free exciton transition, the two‐electron transition of the (D°, X) complex with the donor left in the n = 3 excited state, and most probably the n = 2 donor‐to‐valence band transition.