ZnMgO/n-ZnO/ZnMgO/p-GaN异质结LED的紫外电致发光

Ultraviolet Electroluminescence of ZnMgO/n-ZnO/ZnMgO/p-GaN Heterojunction Light Emitting Diode

利用等离子体辅助分子束外延(P-MBE)技术制备了ZnMgO/n-ZnO/ZnMgO/p-GaN异质结LED。Ni/Au电极与p-GaN、In电极与ZnMgO之间都形成了良好的欧姆接触。在ZnMgO/n-ZnO/ZnMgO/p-GaN异质结器件中观察到了明显的整流特性。异质结的电致发光强度随着注入电流的增大而逐渐增强。室温下在注入电流为20 mA时,电致发光光谱由位于370 nm和430 nm的两个发光峰构成。通过异质结的电致发光光谱与ZnO和GaN材料的光致发光光谱相比较确认:位于370 nm的发光来源于ZnO的自由激子,这主要是利用了ZnMgO/ZnO/ZnMgO的双异质结结构,这种双异质结结构能够阻挡ZnO中的电子进入GaN中,而GaN中的空穴可以进入到ZnO层中。盖层的ZnMgO作为一个限制层,能够提高载流子的复合效率,从而实现ZnO异质结的室温电致激子发光。

The ZnMgO/n-ZnO/ZnMgO/p-GaN heterojunction LED was fabricated by plasmas assistant molecular beam epitaxy（P-MBE） on GaN substrate.Ni/Au contact to the p-GaN layer and In contact to the n-ZnMgO showed a good ohmic contact behavior.This heterojunction showed a good diode rectifying behaviors with turn-on voltage of 2～3 eV.The EL spectra consist of a strong peak at 370 nm and a weaker broad band centered at 430 nm under the forward current at 20 mA.It concluded the 370 nm emission belong to ZnO free exciton recombination,and the 430 nm emission to the defect of GaN substrates by comparing with the PL spectra of ZnO and GaN.By observing the ZnO free exciton emission in ZnMgO/n-ZnO/ ZnMgO/p-GaN,the heterojunctions could be attributed to the double heterojunction structures.The double heterojunctions could block the electrons of ZnO from passing across the ZnMgO layer and entering into the GaN layer.As for holes,the barrier height that hinders the holes in p-GaN from entering into the ZnO is much smaller.