Creation of Artificial Crystal with Atomically-Controlled Group-IV Semiconductor Heterostructures

本计画的目的是发展各种异质材料（如硅、锗、碳等）的原子层-层成长制程。以及通过使用我们建立的化学气相沉积中的朗缪尔型吸附和反应控制技术来创建具有原子控制的IV族半导体异质结构的人工晶体。结果表明，在低温下，在Si Ge IV族半导体表面可以形成C和N原子级共晶膜，并在表面形成Si外延膜。该结果使得能够实现原子层掺杂的IV族半导体异质结构。C的引入改善了Ge表面Si原子层的热稳定性，提高了Si（100）面上应变Si_Ge_x外延膜的临界厚度。<1-x>在应变Si_Ge_x/Si（100）上形成的P原子层上外延生长Si时，用Si_2H_6代替SiH_4作为反应气体，有效地抑制了表面偏析现象，Si_Ge_x/Si异质界面处的最大P原子浓度远远超过10 μ cm~2。<1-x><21><-3><1-x>利用低能量ECR Ar等离子体辐照下的表面反应增强技术，在不加热衬底的条件下实现了原子级平面Si和应变Ge薄膜的高质量外延生长。通过等离子体工艺还实现了原子级氮化控制和随后在氮化表面上的Si外延生长，并且在2nm厚的外延掩埋区中，最大N原子浓度达到约2 × 10~（13）cm~2（原子比为4%）。<21><-3>发现在Si（100）衬底上可以外延生长1nm厚的高应变Ge薄膜。这些结果对于实现高质量的原子控制IV族半导体异质结多层膜具有重要意义。

Purpose of this project is development of atomic layer-by-layer growth process for various kinds of hetero materials (e.g. Si, Ge, C and etc.) and creation of artificial crystal with atomically-controlled group-IV semiconductor heterostructures by using our established techniques of Langmuir-type adsorption and reaction control in chemical vapor deposition. It is found that atomic-order ultrathin film of C and N on Si-Ge group-IV semiconductor surface and subsequent Si epitaxial film on the surface at low temperature can be formed. This result enables to realize an atomic-layer doped group-IV semiconductor heterostructure. It is also found that, by C introduction, thermal stability of a Si atomic layer on Ge surface is improved and critical thickness of strained Si_<1-x>Ge_x epitaxial film on Si(100) is increased. In the case of Si epitaxial growth on the P atomic layer formed on strained Si_<1-x>Ge_x/Si(100), surface segregation phenomenon is effectively suppressed by use of Si_2H_6 instead of SiH_4 as a reactant gas, and maximum P atom concentration exceeds far above 10^<21>cm^<-3> at the heterointerface of Si_<1-x>Ge_x/Si. By using surface reaction enhancement under low-energy ECR Ar plasma irradiation, high quality epitaxial growth of atomic-order flat Si and strained Ge films without substrate heating is realized. Atomic-order nitridation control and subsequent Si epitaxial growth on the nitrided surface are also realized by the plasma process, and maximum N atom concentration reaches about 2x10^<21>cm^<-3> (atomic ratio of 4%) in the 2nm-thick ultrathin buried region. It is found that highly strained 1nm-thick Ge films can be epitaxially grown on Si(100). These results are very useful for realization of the high quality multilayer film with atomically-controlled group-IV semiconductor heterostructures.