Investigation of Novel Tunneling Phenomena in Semiconductors.

Quantum states are created in semiconductor superlattices made of periodic, ultrathin layers of GaAs and GaAlAs grown by molecular beam epitaxy. By controlling the periodic potential, these states are controlled in energy positions, bandwidths and anisotropy, which results in unusual optical and electronic transport properties, as demonstrated from a variety of physical measurements such as resonant tunneling, photoconductivity, resonant Raman scattering and magneto-oscillations. Also, during the course of this study, the molecular beam epitaxy technique has been established to produce atomically smooth and coherent layers, and surface studies have been carried out to yeild important information about surface reconstruction, surface states and oxygen adsorption characteristics. Author