p-type behavior in Na-doped ZnO films and ZnO homojunction light-emitting diodes

The authors report growth of stable Na-doped p-type ZnO films through pulsed laser deposition. Magnetic field dependent Hall-effect measurements demonstrate the firm p-type conductivity of the Na-doped films. The Na related acceptor level was estimated to be ∼164 meV by temperature-dependent photoluminescence and low temperature photoluminescence excitation spectra. ZnO p–n homojunction light-emitting diode consisting of Al-doped n-type ZnO and Na-doped p-type ZnO was fabricated on Si substrates. The diode showed evident rectification behavior with threshold voltage of ∼3.3 eV. The electroluminescence from the diode was observed at 110 K, consisting of three emission bands of 2.24 eV, 2.52 eV, and 3.03 eV from the radiative recombinations in the p-type layer. This work firmly demonstrates that Na could be a good dopant to create stable p-type ZnO.