POINT-DEFECTS AND DEFECT IMPURITY INTERACTION IN CDXHG1-XTE AND OTHER II-VI SEMICONDUCTORS - FACTS AND CONJECTURES

Several aspects concerning the role of point defects and defect-impurity interaction in II-VI semiconductors are reviewed. First, the properties of the cation vacancy in CdxHg1-xTe are re-examined in the light of two experiments (mass-loss measurements, positron lifetime) which point out to a large concentration of vacancy-type defects compared to the hole carrier density. The possibility for the cation vacancy to be a negative-U center and the formation of divacancies are discussed. Second, the case of donor-vacancy pairs is considered. A model of impurity compensation is given which accounts for the doping limits observed in a number of semiconductors in terms of a fundamental energy parameter (dangling bond energy).