1. A transistor device comprising: a semiconductor material comprising first, second, and third portions, wherein the second portion is located between the first and third portions and wherein the first, second, and third portions are doped with dopants of the same polarity and the same or substantially the same concentration; and an electrode connected to the second portion, wherein a current flows between the first and third portions when a voltage is applied to the electrode, and the electrode is doped with dopants of a polarity that is opposite to the polarity of the dopants of the second portion.