Vacancy Related Defects in Antimony-Doped Silicon

Abstract

AbstractHelical dislocations and vacancy aggregates have been reported in lithiumdoped germanium and in diffused silicon. In the present study, defects related to an excess vacancy concentration are examined in as-grown silicon. X-ray topography, etch techniques, and Hall effect are used in determining the conditions of formation of these imperfections. Two distinct types of defects are observed: (1) helical dislocations and (2) dislocation loops. The helical dislocations are identified in the X-ray topographs and correlated to their etch figures. The diameters of the helices in various crystals range from less than 10 to 100 μ. The largest concentration of helices are observed in the initial growth, but prismatic loops or helical segments are also present in the low dislocation density regions of some crystals. The dislocation loop image consists of a pair of opposed arcs. The lengths of images vary from 30 to 400 μ, and the axis of the loop is usually parallel to <110> linage contrast changes with changes in sample orientation, but conclusive Burgers vector determinations are incomplete.The formation of these defects is shown to be directly related to the heat treatment during crystal growth. The total acquisition of vacancies during growth is quite high and is attributed to the “orbital” growth process. In the “orbital” method, the seed check rotates 8-9 rpm about the center of the crucible as the growing crystal rotates 50-60 rpm. A linear relationship exists at room temperature between the vacancy concentration and the antimony impurity concentration. Impurity concentrations were determined independently by chemical and mass spectrograph techniques. A defect complex involving V− and Sb+ in thermal equilibrium is employed to explain this effect.