Photoconduction in Germanium and Silicon

Germanium and silicon are probably the two best known of all of the semiconductors. Their electronic properties have been studied in great detail both theoretically and experimentally. The reason for this is that these two materials are of such great practical importance for transistors and rectifiers. Perhaps less generally appreciated is the fact that both of these materials are excellent photoconductors. Their intrinsic response extends through the entire visible spectrum into the near infrared. When doped with appropriate foreign atoms and operated at low temperatures, these materials are very effective impurity photoconductors with response extending into the far infrared portions of the spectrum.