多孔硅表面冷电子发射的研究

Study on Surface emitting Cold Electrons Based on Porous Silicon Diodes

本文研究了多孔硅（ＰＳ） 二极管表面发射电子的特性。ＰＳ二极管由薄金膜、ＰＳ层、ｎ 型Ｓｉ 衬底和欧姆接触铝背电极组成。在真空中，当在金电极和铝背电极间加适当高的正电压且在收集极板和金电极间存在高外电场时，伴随着可见光，电子均匀地穿过金膜发射出来。电子发射的机理基于ＰＳ层外表面附近的强场效应。在１３－５Ｖ 时得到最大发射电流密度为１０μＡ·ｃｍ － ２ ，最大发射效率为２ ×１０ － ４ 。样品的ＦｏｗｌｅｒＮｏｒｄｈｅｉｍ（ＦＮ） 曲线表现为线性。实验结果暗示有大量的电子直接隧穿或通过界面处电子从Ｓｉ 纳米核的价带向相邻Ｓｉ 纳米核的导带隧穿后被发射向真空。

The characteristics of porous silicon (PS) diodes as electron surface emitting were investigated. The PS diode consist of thin Au film, PS layer, n type Si Substrates and ohmic back contacts. when a sufficient positive voltage is applied to the Au electrode in vacuum, electrons are uniformly emitted through the Au contact layer as well as visible light. The emission mechanism based on the high field effect near the outer surface of PS layer was discussed. The cold emission is explained by the model that electrons are injected from the substrate and drifted towards the top surface by the field within the PS layer and emitted as cold electrons by tunneling through the thin oxide layer at the interface of PS and Au electrode and the Au film as well. The maximum emission current density and efficiency obtained in these samples are 10μA·cm -2 and 2×10 -4 , respectively, at V ps =13 5V. It can be observed that the Fowler Nordheim (F N) plot for these samples follow a linear behavior. These experimental results suggest that at the interface of PS layer and Au film a considerably large number of electrons tunnel directly or tunnel injection from the valence band of Si to the conduction band of the connected Si and then emitted into vacuum.