The Cu-related complex defects in Cu-diffused semi-insulating material were studied by using thermally stimulated current methods. Two new traps, T1 (with ionization energy of 0.25eV) and T2 (0.52eV) were observed. These traps were consistent with 2 acceptor levels, as evaluated by using the van der Pauw method, and the samples changed when the T1 trap appeared with increasing Cu content. The results suggested that the shallower T1 trap compensated not only the mid-gap electron trap (EL2 defect) but also the deep T2 trap. Relative photo-ionization cross-sections were obtained which exhibited a maximum at about 940nm (1.32eV) for the T1 trap and at about 1400nm (0.89eV) for the T2 trap.

K.Kuriyama, K.Tomizawa, S.Uematsu, H.Takahashi: Applied Physics Letters, 1994, 65[6], 746-8