- An impurity which is introduced into a semiconductor material. Such an impurity may be an acceptor impurity, which makes for a p-type semiconductor, or it may be a donor impurity, which makes for an n-type semiconductor. Acceptor impurities include gallium and aluminum, while donor impurities include phosphorus and arsenic. In either case, a semiconductor dopant increases the conductivity of the semiconductor. Also called dopant, or impurity (2).