OPTICAL AND ELECTRICAL-PROPERTIES OF BURIED SEMICONDUCTING BETA-FESI2

By high dose implantation of Fe+ ions into (111)Si substrates and subs equent two-step annealing we fabricated epitaxial Si/beta-FeSi2/Si het erostructures. Photoluminescence measurements reveal a band at about 1 .55 mu m which is attributed to be due to defects in the Si matrix. Ph otothermal deflection spectroscopy at room temperature revealed a dire ct transition at approximate to 0.83 eV, but in addition experimental evidence was found for an indirect transition with an energy of approx imate to 0.78 eV. Measurements of the Hail coefficient as a function o f temperature indicated hole concentrations of 9x10(18) cm(-3) and rem arkably high mobilities of about 104 cm(2)/Vs in buried beta-FeSi2 lay ers at room temperature. By implanting Mn(concentration approximate to 1%) it was possible to fabricate semiconducting Mn0.03Fe0.97Si2 which showed an increased hole concentration of 1.6x10(19) cm(-3) and mobil ities of approximate to 90 cm(2)/Vs.