Atomic-Layr-Epitaxy of Group VI Semiconductors Using Ultra-Activ Gas

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Atomic Layr Epitaxy (ALE) of group VI semiconductors has studied using atomic hydrogen, which does not exist in nature. This atomic hydrogen has been generated by Catalithic effects of hot tungsten filament. By alternative exposure of atomic hydrogen and dichrolo-silane (SiH2CI2), nearly ideal growth rate of 1 monolayr per cycle has been achieved at temperatures around 600C.This ALE cycle has been applied to Ge substrate to evaluate a compositional change at the interface between the epitaxial layr, by using AES and XPS.It was found that Si film is grown in layr-by-layr manner from the first cycle, but that the surface is always covered by Ge monolayr having low surface energy.It was confirmed also that ALE of Ge is possible by changes source to GeH2(C2H5) 2 although the ideal growth rate can not be obtained. This seems to be caused by residing hydrogen atoms at the surface due to low ALE temperature of about 300C.Thus we have changed the source gas to GeH2(CH3) 2 and succeeded to obtain the ideal monolayr growth rate at about 500C.We have also tried the hetero ALE of Ge on Si, but found that there are a lot of C atoms at the surface but a few Ge. Thus we concluded that novel technology should be invented for the first hetero-ALE layr of Ge.