Control of Metal-Compound Semiconductor Interfaces by Formation of Nano-Scale Schottky Contacts and Its Application

这项研究的目的是试图通过形成尺寸可控的纳米肖特基接触来控制金属-化合物半导体界面，从而消除费米能级钉扎。主要研究结果如下：(1)通过电化学方法形成的金属-半导体(M-S)界面由多个金属纳米点组成。通过改变施加的脉冲条件，可以控制点的大小和点的数量。小而均匀的金属点的形成松弛了M-S界面上的费米能级钉扎，增强了肖特基势垒高度对金属功函数的依赖性。这为将肖特基势垒高度控制在肖特基极限附近提供了可能。(2)结合电化学工艺和电子束光刻技术，成功地形成了几十个纳米尺寸的纳米肖特基线栅和几十个纳米尺寸的高度均匀的纳米点阵列。(3)利用导电针尖原子力显微镜研究了单金属纳米点化合物半导体系统中M-S界面的电流传输。利用新研制的纳米肖特基界面器件模拟器，从理论上研究了纳米肖特基界面的传输机制。在单金属点肖特基接触中，金属纳米点尺寸的减小增强了金属功函数的依赖性。然而，环境表面的费米能级钉扎对纳米肖特基栅极的电位控制有很大的影响。(4)利用电化学方法形成纳米肖特基界面的技术被应用于实现各种量子器件，包括基于GaAs基和InGaAs基的量子线晶体管、单电子器件和存储器件。所制作的器件显示了正确和设计的操作，证实了本技术的有效性。

The purpose of this research was attempt to control metal-compound semiconductor interfaces by forming size-controlled nano-Schottky contacts and thereby removing the Fermi level pinning. The main results obtained are listed below :(1)Metal-semiconductor(M-S)interfaces formed by an electrochemical process was found to consist of metal nano-dots. By changing applied pulse conditions, dot size and the number of the dots could be controlled. Formation of small and uniform-size-metal dot relaxes Fermi level pinning at M-S interfaces and enhanced the metal-workfunction dependence of Schottky barrier heights. This opened up a possibility to control Schottky barrier heights toward the Schottky limit.(2)By the combination of the electrochemical process and electron-beam lithography techniques, a few ten nanometer-size nano-Schottky line gates and a few ten nanometer-sized highly uniform nano-dot arrays were successfully formed.(3)Current transport through M-S interfaces in single metal nano-dot-compound semiconductor systems was investigated by a conductive tip atomic force microscopy(AFM). The transport mechanism was theoretically studied by a newly developed device simulator for nano-Schottky interfaces. In the single metal-dot nano-Schottky contacts, reduction of the metal nano-dot size enhanced the metal-workfunction dependence. However, environmental surface Fermi level pinning around the nano-Schottky gates was found to affect strongly the potential control.(4)Nano-Schottky interface formation technology utilizing the electrochemical process were applied to realization of various quantum devices including GaAs-and InGaAs-based quantum wire transistors, single electron devices and memory devices. The fabricated devices showed proper and designed operations, and the effectiveness of the present technology was confirmed.