Study of point defects in CdTe and CdTe:V by cathodoluminescence

The defect structure of CdTe substrates has often been investigated with luminescence techniques. In particular, a luminescence band normally referred as the 1.40 eV band, has been associated with recombination processes involving defects but its nature seems to be complex. Myers et al.’ in their photoluminescence study of CdTe wafers concluded that a significant part of the 1.40 eV band is directly related to surface damage. In other luminescence workslm4 it was found that the emission is also related to bulk defects. Photoluminescence and optical detected magnetic resonance have been used5p6 to study intrinsic defects in CdTe and to relate them to luminescence bands. It has been concluded in Refs. 5 and 6 that the A center (cation vacancy-donor pair) is involved in the 1.40 eV emission. On the other hand a luminescence band in CdTe at about 1.10-1.15 eV has also been reported.6’7 The optical detected and conventional spin resonance measurements6 indicate that the 1.15 eV emission is related to tellurium vacancies. In the present work cathodoluminescence (CL) in the scanning electron microscope is used to investigate the relationship of vacancies in CdTe with the mentioned luminescence bands. Since some impurities appearing in the divalent state in CdTe are situated on substitutional cadmium sites,’ they could influence the cadmium vacancy concentration and the appearance of the corresponding luminescence band. In order to investigate this effect, vanadium doped CdTe was used in addition to undoped material.