Electronic structure of the 1.429-eV complex neutral defect in GaAs from tunable-dye-laser spectroscopy

Tunable-dye-laser excitation spectroscopy is applied to study the electronic properties of the 1.429-eV bound exciton (BE) in Cu-doped GaAs, presumably related to the ${\mathrm{Cu}}_{\mathrm{Ga}}$-${\mathrm{As}}_{\mathrm{Ga}}$ pair. A group of electronic states in the range 1.4285-1.432 eV are observed in more detail than in photoluminescence. BE states derived from both the $J=2\mathrm{}$ and $J=1\mathrm{}$ exchange-coupled multiplets are confined to this spectral region, but the detailed electronic structure is mainly determined by the low-symmetry local strain field. The nonaxial components of the local strain field are found to be important, while the exchange interaction is weaker than previously reported.