Hall-Effect Analysis of Persistent Photocurrents inn-GaAs Layers

The buildup of persistent photoconductivity, presently a controversial phenomenon, is observed by measuring densities and mobilities of photoinduced excess electrons in thin $n$-GaAs layers between successive illuminations. Evidence from this novel type of analysis supports a model assuming charge separation by macroscopic potential barriers. We explain quantitatively how the photon dose logarithmically increases the number, but not necessarily the density, of persisting carriers and ascribe mobility enhancements to screening of ionized impurities.