Electronicband modulation and formation of quantum tunneling structures by atomic-layer control of group-IV semiconductors

本项目的目的是通过对IV族半导体的原子层控制和引入原子级异质结构，研究电子能带调制和量子隧穿结构的形成，以阐明载流子传输/产生/复合过程的新特性，并创造新型电子能带调制半导体。利用B_2H_6和PH_3在Si、Si_<1-x>Ge_x和Ge表面上的表面反应，在抑制混合和孤岛效应的条件下，找到了形成B和P原子层的条件。此外，研究发现，采用Si_2H_6作为反应性比SiH_4更强的反应气体，可以有效地抑制P吸附Si（100）上盖层生长过程中的P偏聚，并使许多P原子进入厚度小于2nm的界面薄膜区域，最大P浓度为3 × 10 ~（-4）<21>cm ~ 2<-3>（原子比6%）。此外，还发现这种P原子层掺杂结构比传统的均匀P掺杂Si显示出更高的霍尔迁移率。通过使用ECR等离子体CVD而不加热衬底，实现了在Si和Ge的（100）表面上具有原子级平坦度的高应变Ge和Si外延生长，并且显示了高应变IV族半导体异质结构的可能性（这是通过常规热CVD工艺难以实现的）。为了获得更高性能的p型共振隧穿二极管，通过研究高质量Si_<1-x>Ge_x/Si异质结外延生长的新条件，得出了增加异质结中Ge含量对达到室温工作是相当有效的结论。这些结果对制备新型电子带调制半导体材料具有重要意义。

Purpose of this project is, by atomic-layer control of group-IV semiconductors and introduction of atomic-order heterostructures, investigation of electronic-band modulation and formation of quantum tunneling structures in order to clarify new properties of carrier transport/generation/recombination processes and creation of novel electronic-band modulated semiconductors. Utilizing surface reactions of B_2H_6 and PH_3 on Si,Si_<1-x>Ge_x and Ge surfaces, conditions for atomic-layer formation of B and P were found under suppression of intermixing and islanding at low temperatures. Additionally, it was found that, by using Si_2H_6 as a more reactive reactant gas than SiH_4,P segregation during capping Si layer growth on a P adsorbed Si(100) could be effectively suppressed and many of P atoms were incorporated in a thin film region at the interface with the thickness below 2 nm and the maximum P concentration of 3x10^<21> cm^<-3>(atomic ratio 6%). Moreover, it was also found that such P atomic-layer doped structures showed higher Hall mobility than the conventional uniformly P doped Si. By using ECR plasma CVD without substrate heating, highly strained Ge and Si epitaxial growth on a (100) surface of Si and Ge with atomic-order flatness was achieved, and possibility of highly strained group-IV semiconductor heterostructures was shown (which was difficult to be achieved by conventional thermal CVD processes). In order to achieve higher-performance p-type resonant tunneling diodes, by investigating new conditions for epitaxial growth of high quality Si_<1-x>Ge_x/Si heterostructures, it is concluded that increase of Ge fraction in the heterostructure is quite effective to reach room temperature operation. These results are very useful to create novel electronic-band modulated semiconductors.