Positron affinity in semiconductors: Theoretical and experimental studies

Knowledge of the positron affinity A(+ ,) a basic hulk characteristic of ma terials, is important to the understanding of positron trapping at interfac es and at precipitates. Theoretical calculations of A(+) for 3C, 4H, and 6H polytypes of SiC, based on various approaches to electron-positron correla tions within the local-density approximation and the generalized gradient a pproximation for positrons, are compared with experimental values obtained via work-function measurements. The disagreement between theoretical and ex perimental values of A(+) is discussed in terms of difficulties in the prec ise measurement of the positron work function and the possible inadequacy o f contemporary approaches to electron-positron correlation in semiconductor s. [S0163-1829(99)02303-6].