Fabrication of Super-Heterostructures for Advanced Optoelectronic Quantum Devices

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New type of light emitting devices or electron devices for future LSI technology using Super-heterostructures are studied. Intersubband quantum cascade lasers using CdF_2-CaF_2 heterostructures have been proposed and novel crystal growth technique Nanoarea-Local-Epitaxy has been demonstrated. Energy subbands in the quantum wells has been confirmed using resonant tunneling diode with double- and triple-barrier structures. And moreover, spontaneous emission from CdF_2-CaF_2 single cascade structures has been observed for the first time.Results obtained in this research are as follows.(1) Near-infrared electroluminescence from a single-period (CdF_2/CaF_2) inter-subband quantum cascade structure on a Si substrate has been observed for the first time. The CdF_2/CaF_2 heterostructure is a good candidate for realizing a Si-based short-wavelength quantum cascade laser because of its large conduction band discontinuity of 2.9 eV and small lattice mismatch with the Si substrate. In the experiment, an active region consisting of (CdF_2/CaF_2) heterostructures was grown epitaxially on the Si substrate by molecular beam epitaxy, and an Au/Al electrode was evaporated on the active region. The wafer was polished mechanically and cleaved. Electroluminescence from the device was observed in the near-infrared region at room temperature for the first time.(2) Epitaxial growth of high-quality CdF_2/CaF_2 heterostructures on Si(100) substrate has been demonstrated using Nanoarea-Local-Growth and in-situ post-annealing for solid phase epitaxy. Using this method, room temperature high peak to valley current ratio (>10^5) of CdF_2/CdF_2 resonant tunneling diode structures has been demonstrated on Si(100) substrate for the first time.