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

本研究的目的是通过原位电化学法去除费米能级钉扎来实现各种金属-化合物半导体(M-S)界面的“肖特基极限”，并将这一过程应用于各种器件。主要研究结果如下：1)一种新的原位电化学方法使InP、GaAs和GaN的肖特基接触具有与金属功函数强烈相关的肖特基势垒高度(SBHs)，特别是对于Pt/n-InP和Pt/n-GaAs接触，SBHs分别大于0.86和0.92 eV。这些值接近肖特基极限。2)原位电化学方法制备的M-S界面没有氧化物过渡层，没有界面应力，也没有工艺诱导的缺陷能级。3)详细的原子力显微镜测量表明，电化学沉积是由纳米金属颗粒的形成引发的。进一步的沉积并没有增加颗粒的尺寸，但增加了颗粒的密度。SBH值与颗粒分布有很强的相关性。最小颗粒的分布最均匀时，铂/n-InP接触的SBH值最高。利用带有导电针尖的AFM系统进行的I-V测量表明，在InP和GaAs上的单个铂颗粒中实现了如此高的SBHs。4)上述结果可以解释如下：在优化的条件下，低能电化学过程在不引起半导体表面大范围无序的情况下形成了细小的金属纳米颗粒。该界面没有氧化物夹层、界面应力和工艺缺陷。这导致了费米能级钉扎的去除和强烈依赖于金属功函数的SBH值。5)原位电化学过程被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