n-ZnO/i-MgO/p-GaN异质结发光二极管

用等离子体辅助分子束外延的方法生长了n-ZnO/i-MgO/p-GaN异质结发光二极管。I-V测量表明其具有典型的二极管整流特性。电致发光峰位于382nm,通过与n型ZnO和p型GaN的光致发光谱比较,其发光峰位与线形都与ZnO的自由激子发射一致,表明该电致发光来自于ZnO的自由激子发射。通过Anderson模型比较了n-ZnO/i-MgO/p-GaN和n-ZnO/p-GaN异质结的能带示意图,证明了由于MgO层的插入抑制了ZnO向GaN层中的电子注入,且有利于空穴向ZnO层注入,从而实现了ZnO层中的电注入发光。

n-ZnO/i-MgO/p-GaN Heterojunction Light-emitting Diodes

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 10¹⁸cm^-3 and the resistivity of 0.6Ω·cm.The hole concentration of p-GaN is about 10¹⁷cm^-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.