高偏压Al-MgF_2-Au(Cu)隧道结的结构、导电和发光

Structure, Current transport and Light emission of the Al--MgF_2--Au high bias light--emitting tunnel junctions

本文对我们所发明的Al-MgF_2-Au(Cu)薄膜发光器件[1]的内层结构、导电过程和发光机理做了进一步的研究,对以前报导的一些结论作了原则性的修正:前所报导的Al-MgF_2-Au结内层的实际结构是Al-Al_2O_3-MgF_2-Au,而不仅仅是Al-MgF_2-Au;且正是由于Al_2O_3膜的存在,方才使MgF_2膜得以具有绝缘作用。是来之负电极的隧穿电子,而不是MgF_2膜内的热电子,导致了该结的导电和发光。据此,本文对该结在高偏压下的logL∝V的新型伏安特性曲线及其发射光谱中位于3.4ev(3600)附近的截止频率给出了理论解释;从而得出:电子隧穿,激发SPP,然后SPP退激发光的这一物理过程,即使在Al、Au两电极间的绝缘层厚度由3μm左右增加到20μm左右时,也可依然存在。

The struc! ure, currant transport process and light emission mechanics of Al-MgF_2-Au tunnel junctions which had been described in the authors' other paper are further studied here. In this paper, the authors correct some of their former conclusions, and concludeas follows: (1) The real structure of Al-MgF_2-Au tunnel junctions is Al-Al_2 O_3-MgF_2-Au, not pure artifi- cial potential barrier tunnel junctions. Naturally produced Al_2O_3 plays an important role in forming the junctions. (2) The transport process of electrons is, at first, electrons in Al films tunnel to the conduction bands of Al_2O_3-MgF_2 double insulators, and then, inject to the Au film posi- tive electrode. Tunnelling and subsequent normal transportation appear in the process simultaneously. And based on the model, the authors have given an interpretation, which is identical with experimental results, to the new voltage-current curve-log I∝V of the tunnel junctions at high bias. (3) After analysing the cut-off frequence of light emission spectrum of the tunnel junctions, the writers provide light emission of the tunnel junction is produced by the decouple of the SPP excited by tunnelling el- ectrons. And so there is a cut-off frequence 3, 4 eV (3600A). From the light emission of Al-MgF_2-Au junctions, therefore, the authors conclude the physical process of electrons' tunnelling exciting SPP and then the SPP's decoupling may be still in existence even if the thickness if the insulator film between Al and Au electrodes is increased from about 3nm to about 20nm.