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 similar to 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 similar to 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. (C) 2008 Elsevier Ltd. All rights reserved.