Thermal ionisation and photoionisation properties of deep traps in n type CdTe

Abstract Physical properties of some native deep electron traps in n type CdTe have been investigated by means of capacitance techniques. Using D.L.T.S. measurements, 4 levels labelled E 1 to E 4 have been detected with apparent ionisation energies in the range of 0.24–0.88 eV and unusually small electron capture cross sections σ c ≃ 10 -20 cm 2 . Deep Level Optical Spectroscopy (D.L.O.S.) has been used to measure the spectral dependence of the photoionisation cross section of the defects. In case of level E 4 , it has been possible to observe both transitions Γ 8V → E 4 and E 4 → Γ 6V . Interpretation is made in terms of one dimensional configuration coordinate diagrams. From these, it is concluded that levels E 2 E 3 E 4 are weakly relaxed while level E 1 is strongly coupled to the lattice.