ZnO p-n junction light-emitting diodes fabricated on sapphire substrates

A ZnO p-n junction light-emitting diode (LED) was fabricated on a-plane Al2O3 substrate by plasma-assisted molecular-beam epitaxy. NO plasma activated by a radio frequency atomic source was used to grow the p-type ZnO layer of the LED. The current-voltage measurements at low temperatures showed a typical diode characteristic with a threshold voltage of about 4.0 V under forward bias. With increasing temperature, the rectification characteristic was degraded gradually, and faded away at room temperature. Electroluminescence band of the ZnO p-n junction LED was located at the blue-violet region and was weakened significantly with increase of temperature. This thermal quenching of the electroluminescence was attributed to the degradation of the diode characteristic with temperature. (c) 2006 American Institute of Physics