Properties of phosphorus-doped (Zn,Mg)O thin films and device structures

The properties of phosphorus-doped (Zn,Mg)O polycrystalline and epitaxial thin films are described. The as-deposited (Zn,Mg)O:P films are n type with high electron carrier density. High resistivity is induced in the films with moderate temperature annealing, which is consistent with suppression of the donor state and activation of the deep acceptor. The resistivity of the as-deposited and annealed film is an order of magnitude higher than similar samples with no Mg, consistent with a shift in the conduction band edge relative to the defect-related donor state. The capacitance-voltage characteristics of annealed metal/insulator/P-doped (Zn,Mg)O structures in which the (Zn,Mg)O is polycrystalline exhibit p-type polarity. In addition, multiple polycrystalline devices comprising n-type ZnO/P-doped (Zn,Mg)O thin-film junctions display asymmetric I–V characteristics that are consistent with the formation of a p-n junction at the interface, although the ideality factor is anomalously high.