Binding energy of an electron to a three-defect-complex in CdTe

Recent measurements on halogen doped CdTe shows an unidentified electron trapping level at 0.05 eV. Using a mass action approach to self compensation involving a substitutional halogen, X_Te, and a cadmium vacancy, V_Cd, it can be shown that in addition to the two-defect complex, V_CdX_Te, the three-defect complex (V_Cd2X_Te) is present in substantial concentrations. A calculation of the binding energy of an electron to this three-defect-complex using the configurational interaction and one electron wave function, leads to a bound state with a depth about right for the unidentified level.