Properties of defects in Hg(1-x)Cd(x)Te

This final report covers the progress made over the July 1, 1981 through September 30, 1984 period. The majority of the contract effort was focused in this period on systematic investigations of the basic physics of defects in HgCdTe. Detailed electrical characterization of LPE HgCdTe has been carried out. The normal range of values in carrier concentrations, mobilities and minority carrier lifetimes was established by Hall effect and photoconductive decay lifetime measurements. The total equilibrium concentration of cation vacancies was studied qualitatively and compared with model calculations. The results show that the doubly ionized vacancy state is dominant and the cation vacancy formation energy (Ef) is found to be 0.9 + or - 0.1 eV for Hg1-xCdxTe and nearly independent of the Cd composition x. Te precipitates in CdTe have been characterized by Auger spectroscopy, X-ray diffraction and Raman spectroscopy. The X-ray results show that precipitated Te in Bridgman-grown CdTe crystals has the same structural phase as observed in elemental Te under high pressure. Auger and Raman microprobe spectroscopy were carried out to confirm Te precipitates in CdTe and identify the symmetry of the Te precipitates. Acceptor ionization energies (EA) in Hg1-xCdxTe material were also investigated as a function of annealing temperature. These EA values, as observed from Hall measurements, decrease from 20 to 10 meV as anneal temperature decreases from 488 to 347 C.