p-Type ZnO on sapphire by using O2-N2 co-activating and fabrication of ZnO LED

A co-activating route was employed to fabricate ZnO light-emitting diode (LED) by using molecular beam epitaxy. N2 was used as the acceptor dopant source and O2 was used as assistant gas for N2 decomposing more than only oxygen source. Emission spectra of the N2+O2 mixture plasma were monitored in situ in order to adjust growth parameters timely. Under the assistance of O2, N atoms content in the plasma of the mixture shows a significant increase compared to the case without O2 assistance. Electrical measurements of the as-grown p-type ZnO on sapphire show a carrier concentration of 1.2×18 cm−3 and a mobility approaching 1 cm2 V−1 s−1. A ZnO LED was fabricated by depositing undoped n-type ZnO on the p-type layer. The turn-on voltage at 100 K is about 3.70 V, which approaches the bandgap of ZnO. Electroluminescence spectra show two bands: one is centered at 423 and the other centered at 523 nm, respectively.