Acceptor states in CdTe and comparison with ZnTe. General trends

Abstract

New experimental results are reported for the acceptors Li, Na, and P in CdTe. Their excited states are obtained from photoluminescence studies performed with a tunable dye laser. "Two-hole transition" lines from these acceptors are observed for the first time. Moreover, a new unidentified phonon with an energy of 19 meV is observed in Li- and Na-doped samples. These new results complete our understanding of the acceptor states in CdTe concerning the impurities Li, Na, Cu, Ag, and Au on Cd sites and N, P, and As on Te sites. The wealth of these data, together with similar results obtained in ZnTe, allows one to make a comparison between these two materials. It is shown that, for the cation-site (i.e., Zn or Cd) substitutional acceptors in particular, the central-cell corrections are practically independent of the nature of the semiconductor. The valence-band parameters, and thus the effective-mass acceptor states in CdTe and ZnTe, are similar. The results shown here provide a good basis for some theoretical investigations on acceptor impurites in II-VI compounds.