Band Engineering on Alloy of Fluorides for Heterodevices

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The purpose of this research was the artificial control of energy level of conduction band on fluoride alloys of composed of CaF_2 and CdF_2 which were epitaxially grown on Si substrates, and demonstrate feasibility of the technique to be applied for quantum effect hetero devices.First, the CaF_2 buffer layer which was expected to be necessary to obtain good Ca_xCd_<1-x>F_2 alloy on Si was investigated. It was found that the CaF_2 buffer layer was able to be thin down to two mono-layers keeping good crystallinity and morphology of overgrown Ca_xCd_<1-x>F_2 layers. The minimum thickness was fond to fit applications of various tunnel devices since electrons can tunnel the layers.The internal photon emission(IPE) analysis was carried out on the Au/Ca_xCd_<1-x>F_2/Si(111) diode structures, where photo emission current depending on wave length ofexiting light. As a result, it was shown that energy level of conduction bad edge of Ca_xCd_<1-x>F_2 was lineally changed depending on the composit … More ion of Ca_xCd_<1-x>F_2, for the first time. It was also confimied that the energy barrier of conduction bad edge of CaF2 for that of Si was 2.3 eV through the IPE measurement, and that the value was consistent with those obtained by X-ray photoelectron spectroscopy in the previous work From these results, it was indicated that band engineering on the fluoride alloy system, Ca_xCd_<1-x>F_2, was promising.Finally, double barrier resonant tunneling diodes (RTDs) in which the Ca_xCd_<1-x>F_2 was employed in the barrier layers were fabricated, and they were compared to the conventional diodes in which pure CaF2 was employed in the barrier layers. The RTDs using Ca_xCd_<1-x>F_2 barrier exhibited good negative differential current-voltage characteristics. Furthermore, higher current density in spite of thicker barrier kyer on the RTD using Ca_xCd_<1-x>F_2 barrier than those using pure CaF2 was observed, which indicated controllability of barrier height on the RTDs by composition of the fluoride alloy system. Less