Si/SiOx/Si Hole-Barrier Fabrication for Bipolar Transistors Using Molecular Beam Deposition

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Abstract
SiO x layers were deposited on Si substrates in a Si MBE system by codeposition of Si and O2. The oxygen concentration increased as the deposition temperature decreased and approached the results of SiO2 stoichiometry. O2 pressure was 5×10-5 Torr and the Si deposition rate was 0.2 Å/s. Composition was determined by using X-ray photoelectron spectroscopy and Auger electron spectroscopy, and the electric properties of its MOS capacitor were measured. The growth procedure used here offers high controllability in the thickness of the deposited SiO x layer and permits subsequent Si growth in the same Si-MBE chamber. Such Si/SiO x /Si structures, which may be applied to the hole-barrier between the base and emitter layers in a bipolar transistor, were also successfully grown using this method. The tunneling currents for electrons and holes in such structures with SiO x thickness of 5–60 Å were measured. One-order-larger tunneling currents for electrons than those for holes were measured at the same SiO x thickness above 30 Å.