Electronic properties of an electron-attractive complex neutral defect in GaAs

This Rapid Communication reports the first detailed optical study of a complex neutral defect in GaAs (probably ${\mathrm{Cu}}_{\mathrm{Ga}}$-${\mathrm{As}}_{\mathrm{Ga}}$), binding an exciton at 1.429 eV. Zeeman data at 10 T for the bound exciton are analyzed in detail, considering both the electron-hole exchange interaction and the local strain field. The defect has an electron-attractive local potential and a tensional local strain field. The g value for the deeply bound electron $g_e$=0.9 is strongly modified from the value $g_e$=-0.46 for a shallow donor, while the bound hole remains effective-mass-like.