Influence of Extended Defects and Native Impurities on the Electrical Properties of Directionally Solidified Polycrystalline Silicon

The electrical properties of dislocations and grain boundaries (GB) in directionally solidified polycrystalline silicon were extensively studied as a function of the carbon, oxygen, and nitrogen content, as well as of the relative grain orientation. As a first result of this study we obtained the experimental evidence that the oxygen and carbon content are not independent variables of the material. Therefore, the density and the electrical activity of dislocations are shown to be strongly dependent on the amount of oxygen‐carbon compensation. As a second result, experimental evidence was also achieved which demonstrated that grain boundaries are strongly passivated and that recombination losses at GB do not present any relevant relationship with mutual crystallographic orientations of the grains. It appears, therefore, that a careful choice of the growth and postgrowth conditions yields a material which behaves like crucible grown single‐crystal silicon.