Below 30°K zinc‐doped germanium exhibits a number of unusual photo and temperature effects when the lowest zinc‐acceptor levels have been filled by electrons from compensatory antimony impurities. These effects include negative photoconductivity, a discontinuity in the temperature dependence of the sample conductivity, as well as the storage of free electrons produced by intrinsic photoexcitation. Hole trapping by the Zn atoms which are singly or doubly ionized is the prime source of these effects. A simple theory is presented which qualitatively explains all of the observed effects and quantitatively fits the data in those areas that are accessible to rigorous measurement.