Properties of Germanium Doped with Iron. II. Photoconductivity

Abstract

Photoconductivity in $n$- and $p$-type Fe-doped Ge was measured at 77\ifmmode^\circ\else\textdegree\fi{}K. The impurity photoconduction in both types has approximately the same spectral dependence, indicating ionization energies of about 0.3 ev. The intrinsic photoconductive response measured at 0.83 ev was found to be a function of sample composition, the photosensitivity increasing as the samples became more $n$-type. Intrinsic photosensitivity and the time of response seem linearly related. For $n$-type samples of highest sensitivity the minimum detectable radiation level at 0.83 ev was estimated to be 2\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}13}$ watt. In such samples quenching effects were found in the spectral region from 0.3 ev to 0.7 ev. Experimental results are discussed in terms of a model in which the impurity center is capable of accepting two excess electrons.