Recently

ZnO has being paid more attention because of potential applications in ultraviolet light(emitting) diode and laser diode.However

it is very difficult to fabricate p-type ZnO due to serious self-compensation effect

which results in no great progress in p-n homojunction diodes.ZnO heterojunction as another route has been paid attention except the effort on the fabrication of p-ZnO.One attractive heterojunction is ZnO/GaN heterojunction because of similar crystal structure and small lattice mismatch of 1.8%.However

the emission of GaN plays a dominant role in the electroluminescence spectra of ZnO/GaN heterojunction light emitting diode.The main reason was analyzed

the new heterojunction was designed by introduced into MgO i-layer by plasma-enhanced molecular beam epitaxy(P-MBE)

and n-ZnO/i-MgO/p-GaN heterojunction light emitting diode was fabricated.The electrical properties of each layer were determined by Hall effect measurement.The ZnO shows n-type conductivity with the carrier concentration of 10

18

cm

-3

and the resistivity of 0.6Ω·cm.The hole concentration of p-GaN is about 10

17

cm

-3

.

I-V

curve show rectification diode behavior in this heterojunction and have turn-on voltage of 4V.The bright ultraviolet electroluminescence at 382 nm was observed in the room temperature electroluminescence spectrum.It is concluded that this emission is originated from the(recombination) in ZnO layer by comparing with photoluminescence spectra of ZnO and GaN.According to(Anderson) Model

it is proved that the injection of MgO layer can limit effectively electrons into p-GaN layer in this heterojunction due to very small electron affinity and wide energy band of MgO.It is very hopefull to (realize) the stimulated emission of ZnO using these heterojunctions by the improvement of(crystal) quality and the optimization of device structure.