Fabrication of Nitrogen Doped p-ZnO and ZnO Light-Emitting Diodes on Sapphire

Nitrogen-doped p-type ZnO thin films were grown on c-plane sapphire (Al2O3) substrates by plasma-assistant molecular beam epitaxy, where O-2 and N-2 were introduced via a RF plasma source simultaneously. In situ optical emission spectra of the plasma were employed to monitor the chemical species in the active gas sources, one of the most important growth parameters. By adjusting the growth parameters, we confirm the optimal condition for p-type doping growth. The reproducible p-type ZnO thin films have the hole concentration (N-A - N-D) up to 1.0 x 10(18) cm(-3) and the resistivity of 6 Omega cm. A ZnO LED was fabricated by depositing undoped n-type ZnO on the p-type layer. Electroluminescence spectra centered about 430 nm were obtained even at 350 K.