Group Research
Group Alumnus, Dr. Di Liang
Prof. Hall's compound semiconductor materials and device research is focused on understanding and developing new applications of native oxides for optoelectronic, electronic, and integrated optics devices. We have pioneered a new “non-selective” wet thermal oxidation technique for oxidizing low-aluminum-content and Al-free III-As compound semiconductor alloys. Presently, GaAs-based semiconductor lasers, optical waveguides and electronic devices are being designed, fabricated and characterized. New approaches are being explored for realizing low-loss, high-index-contrast (i.e., strong optical confinement) heterostructure waveguides for high-efficiency semiconductor lasers and photonic integrated circuits applications. Using our non-selective oxidation process, high-index-contrast ridge waveguide lasers incorporating a bent resonator waveguide with a radius of curvature as small as 6 microns have been achieved. An oxidation smoothing technique has been demonstrated for reducing the etched sidewall roughness in AlGaAs/GaAs heterostructures to as low as 1 nm to significantly reduce waveguide scattering loss. Ongoing research on the use of InAlP native oxides for metal-oxide-(compound) semiconductor (MOS) device applications has recently led to the demonstration of record microwave-performance for a GaAs MOSFET. InAlP native oxides have also been shown to have excellent host properties for optically-active Er3+ ions (strong room temperature photoluminescence intensity with long ~8 mS decay times, high Er solubility, broad emission bandwidth), and are under further investigation for their potential to enable GaAs-based monolithically-pumped erbium-doped waveguide lasers and amplifiers.