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

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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.