"Realization of Schottky-limit at metal-semiconductor interfaces and its application to electron devices"

本研究的目的是实现“肖特基极限”的各种金属化合物半导体（M-S）接口，通过消除费米能级钉扎使用原位电化学过程，并将此过程应用到各种设备。1）一种新的原位电化学工艺使我们能够制备出InP、GaAs和GaN的肖特基势垒高度与金属功函数密切相关的肖特基接触，特别是Pt/n-InP和Pt/n-GaAs的肖特基势垒高度分别大于0.86和0.92eV。结果表明，原位电化学方法制备的M-S界面没有氧化物夹层，没有界面应力，也没有工艺诱导的缺陷能级。进一步沉积并不增加颗粒的尺寸，但增加了颗粒的密度。SBH值与颗粒分布具有很强的相关性。最均匀分布的最小的颗粒得到最高的SBH值的Pt/n-InP接触。使用具有导电尖端的AFM系统的I-V测量显示，在InP和GaAs上的单个Pt颗粒中实现了如此高的SBH。4）上述结果可以解释如下：在优化的条件下，低能量电化学过程形成精细的金属纳米颗粒，而不会在半导体表面上引起大程度的无序。该界面没有氧化物夹层、界面应力和工艺引起的缺陷。这导致费米能级钉扎的去除和强烈的金属功函数依赖的SBH值。5）原位电化学过程成功地应用于亚微米T形的形成

The purpose of this study is to realize the "Schottky limit" for various metal-compound semiconductor (M-S) interfaces by removing Fermi-level pinning using an in-situ electrochemical process and to apply this process to various devices. The main results obtained are listed below :1) A novel in-situ electrochemical process enables us to produce Schottky contacts with strongly metal-workfunction dependent Schottky barrier heights (SBHs) for InP, GaAs and GaN.Particularly, SBHs higher than 0.86 and 0.92eV were achieved for Pt/n-InP and Pt/n-GaAs contacts, respectively. These values are close to those in the Schottky limit.2) The M-S interfaces prepared by the in-situ electrochemical process were found to possess no oxide interlayers, no interface stress as well as no process-induced defect levels.3) Detailed AFM measurements revealed that the electrochemical deposition was initiated by formation of nm-sized metal particles. Further deposition did not increase the particle size but increased density of particle. The SBH values exhibited a strong correlation with the particle distribution. The most uniform distribution of the smallest particles gave highest SBH values for Pt/n-InP contact. An I-V measurements using AFM system with conductive tip revealed that such high SBHs were realized in single Pt particles on InP and GaAs.4) The above results can be explained as follows : Under optimized conditions, the low-energy electrochemical process forms fine metal nano particles without causing a large degree of disorder on the semiconductor surface. The interface is free from oxide interlayers, interface stress and process-induced defects. This leads to removal of the Fermi-level pinning and to strongly metal-workfunction dependent SBH values.5) The in-situ electrochemical process was successfully applied to formation of sub-micron T-shaped