This paper introduces a simple and attractive calculation technique to evaluate the directionally solidified ingot characteristics type when considerable donor and acceptor impurities exist simultaneously in a silicon melt. The threshold limit of boron concentration in n-type ingot is C-OB = 0.4375C(OP) and when the boron concentration is above the threshold value, the bottom of the ingot, The bottom of the ingot exhibits boron domination due to its higher effective segregation coefficient. The fractions where polarity changes from n-type to p-type and vice versa are calculated for different boron/phosphorus concentration ratios. In addition, Calculations of the required counter-doping concentration to make use of heavily boron or phosphorus-doped recycled silicon feedstock are made and simple examples are given. (C) 2008 Elsevier B.V. All rights reserved.