ELECTRONIC LEVEL DIAGRAM AND STRUCTURE OF METASTABLE CENTERS IN CDF2-GA AND CDF2-IN SEMICONDUCTING CRYSTALS

A study is reported of the optical properties of wide-gap, predominant ly ionic cadmium fluoride crystals in photo-and thermally stimulated t ransformations of metastable indium and gallium centers. An analysis o f these properties leads one to a conclusion of gallium having two met astable states (two types of deep centers), The jeep-center binding en ergies and the barriers separating the shallow (hydrogenic) and deep c enters have been determined for both impurities. Configuration-coordin ate diagrams are developed, and microscopic models for the deep center s are proposed. It is concluded that these centers are identical with the metastable DX centers in typical semiconducting crystals. Thus cad mium fluoride is the most ionic among the crystals where DX centers ha ve thus far been found. The potential of using such crystals for optic al information recording is discussed. (C) 1997 American Institute of Physics.