The electrical characteristics of ZnS:Mn alternating‐current thin‐film electroluminescent (ACTFEL) devices grown by atomic layer epitaxy are assessed as a function of the thickness of the phosphor layer using capacitance‐voltage (C‐V) and internal charge‐phosphor field (Q‐Fp) analysis. Deviations from the ideal in the measuredC‐VandQ‐Fpcharacteristics are ascribed to the generation of space charge in the phosphor layer during ACTFEL device operation.C‐Vovershoot deviations are correlated to space charge generation via a simulation employing a single sheet of charge model which assumes that the centroid of the generated space charge is located at a discrete sheet within the phosphor. Space charge generation in these atomic layer epitaxy (ALE) ZnS:Mn ACTFEL devices is ascribed to impact ionization of the zinc vacancy portion of chlorine‐zinc vacancy self‐activated defect complexes. A thermodynamic argument is provided which suggests that zinc vacancies are created via self‐compensation of ZnS when the ZnS is unintentionally doped with chlorine. It is contended that space charge generation could even be desirable in ALE ZnS:Mn ACTFEL devices because it leads to better aging stability and improved performance. ©1995 American Institute of Physics.