  Optical properties of ZnMnO layers grown at low temperature by Atomic Layer
Deposition and Metalorganic Vapor Phase Epitaxy are discussed and compared to
results obtained for ZnMnS samples. Present results suggest a double valence of
Mn ions in ZnO lattice. Strong absorption, with onset at about 2.1 eV, is
tentatively related to Mn 2+ to 3+ photoionization. Mechanism of emission
deactivation in ZnMnO is discussed and is explained by the processes following
the assumed Mn 2+ to 3+ recharging.
