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

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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.