ATOMIC-LAYER CONTROLLED SUPER-HETEROEPITAXY AND PROPERTIES OF LANTHANOIDE/SEMICONDUCTOR STRUCTURES

人们对稀土元素与III-V半导体的结合越来越感兴趣。其中一个原因是稀土与v族元素反应形成镧系元素，如ErP和ErAs。由于镧系元素表现出半金属性质，在半导体异质结构中加入镧系元素层有望促进量子限制系统和新型电子器件中的新物理。在这个研究项目中，我们研究了在InP衬底上的ErP的原子层控制的超异质外延。外延所用的气体流动顺序与铒的“δ掺杂”基本相同。实验结果总结如下：1)卢瑟福后向散射（RBS）测量表明，样品中的Er片密度随Er暴露时间线性增加，即使在80 min也没有饱和，并且在Er暴露时间为23 min时，Er原子的数量相当于1个单层（ML）。2)在4.2K光致发光（PL）测量中，由于4f-壳层内跃迁，观察到与Er相关的特征发射。3)同步辐射x射线晶体截断棒（CTR）散射测量清楚地表明，Er原子与P原子以NaCl晶体排列合并，荧光检测扩展x射线吸收精细结构（EXAFS）测量结果也支持了这一结论。所得到的Er分布几乎是对称的，其特征是被限制在几个微米厚度的Er原子。4)利用原子力显微镜（AFM）和超高真空扫描隧道显微镜（UHV-STM）观察了ErP在InP上的外延。表面形貌与衬底温度和er暴露时间密切相关。沿[110]方向产生错配位错，形成空洞和孔洞。

There has been increasing interest in the combination of rare-earth (RE) elements and III-V semiconductors. One of the reasons is RE reacts with group-V elements to form lanthanoides such as ErP and ErAs. Incorporation of the lanthanoide layrs in semiconductor heterostructures is expected to facilitate new physics in quantum-confined systems and novel electronic devices, since the lanthanoides exhibit semimetallic behavior.In this research project, we investigated atomic-layr controlled super-heteroepitaxy of ErP on InP substrates. Gas-flow sequence used for the epitaxy was basically the same as that for "delta-doping" of Er. Results obtained experimentally are summarized as follows ;1) Rutherford backscattering (RBS) measurements showed that Er sheet density in samples increases linearly with Er-exposure duration and exhibits no saturation even at 80 min, and that Er atoms, corresponding to 1 mono-layr (ML) in number, are incorporated during the Er-exposure duration of 23 min.2) In 4.2K photoluminescence (PL) measurements, characteristic Er-related emissions due to 4f-intra shell transitions were observed, which were quite different from those in InP doped uniformly with Er.3) X-ray crystal truncation rod (CTR) scattering measurements using synchrotron radiation revealed clearly that Er atoms are incorporated having the NaCl crystal arrangement with P atoms, which was also supported by fluorescence-detected extended X-ray absorption fine structure (EXAFS) measurements. The resultant Er profiles were almost symmetric and were characterized by Er atoms confined in several MLs in thickness.4) Epitaxy of ErP on InP were observed by atomic force microscope (AFM) and ultra-high vacuum scanning tunnelling microscope (UHV-STM). Surface morphology depended strongly on substrate temperature and Er-exposure duration. There were generation of misfit dislocations along the [110] direction and formation of voids and holes.