Single Crystal Growth and Stoichiometory Control of Ecologically Friendly Semiconductor β-FeSi_2

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Ecologically friendly semiconductor β-FeSi_2 has been intensively investigated in recent years as a promising material for future optoelectronic devices, because β-FeSi_2 has theoretical direct band gap 0.85 eV that fits the minimum absorption window of the quartz fiber. In addition, fabrication of β-FeSi_2 based light emitters or detectors on Si substrate leads to optical integrated circuits. Although characterizing the high quality single crystal reveals its intrinsic properties as well as the effects of impurities and native defects caused by the deviation from stoichiometry, a high quality single crystal has not been grown. In the present study, bulk single crystals and thin epitaxial films were grown by chemical vapor transport (CVT) and molecular beam epitaxy, respectively.Transport mechanism and optimum growth condition were clarified for CVT growth. CVT grown single crystal showed a clear photoluminescence and a high electron mobility at a low temperature. In addition, a high quality β-FeSi_2 epitaxial film with the thickness of 180 nm has been successfully grown for the first time on hydrogen terminated Si(111) at 580℃ by using solid source molecular beam epitaxy. The β-FeSi_2 film grown with stoichiometric Fe/Si source flux ratio 1:2 has a superior morphology and crystallinity comparing to the published results of the films grown by other methods.