Very Shallow Trapping State in Doped Germanium

Submillimeter photoconductivity in doped germanium has been studied with a lamellar grating spectrophotometer. The observed photoconductivity is ascribed to a shallow trapping state such as $D^{-}$ or $A^{+}$. However, our spectral peak energies and shapes are quite different from those previously reported by Gershenzon, Gol'tsman, and Mel'nikov.