Nitride Quantum Wells and Photonic Structures - Growth, Optical Studies, and Applications

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This project pursues several interconnected research areas: 1) Optimizing III-nitride material quality; n- and p-type doping, particularly for AlGaN ternary alloys and InAlGaN quaternary al-loys with relatively high Al contents (x 0.5); and reduction of dislocations and line defects. When submicron-strip lateral epitaxial overgrowth is employed, relaxation of excess strain at the mesa edges may dominate, resulting in fewer dislocations above the window region. The poten-tial of lattice-matched quaternary quantum wells (QWs) of GaN/InAlGaN as active media for UV emitters with improved performance will also be explored. 2) Fabricating and processing III-nitride wavelength-scale photonic structures and devices. E-beam lithography patterning and plasma dry etching to create wavelength-scale photonic structures and devices will be studied. Unique properties of III-nitrides make them very attractive for the generation, guiding, and switching of light, and new architectures for integrating III-nitride photonic components (e.g., resonators, waveguides, emitters, detectors, etc) onto single chips will be explored to lay the foundation for achieving integrated photonic circuits based on III-nitrides for a wide range of ap-plications. 3) Deep UV time-resolved nano-optical studies. A specially designed deep UV pico-second time-resolved nano-optical spectroscopy system will be used for probing optical proper-ties [photoluminescence (PL), electro-luminescence (EL), etc.] of semiconductor materials and photonic devices with time-resolution of a few ps, spatial resolution of 50 nm, and wavelength range spanning from IR to deep UV (to 195 nm). This system integrates a deep UV femtosecond laser spectroscopy system with a deep UV near-field-scanning-optical-microscopy (NSOM)/AFM system. It will be utilized to probe carrier dynamics, optical transitions, as well as defect properties in nitride materials and QWs, especially in AlGaN alloys, GaN/AlGaN and GaN/InAlGaN QWs with high Al content (x0.5). The aim is to gain new understanding and methods of controlling optical and optoelectronic properties. The emission and light propagation properties in wavelength-scale emitters and waveguides will also be investigated to provide input for improved integrated photonic device design. %%% The project addresses fundamental research issues in a topical area of electronic/photonic materi-als science having high technological relevance. An important feature of the project is the strong emphasis on education, and the integration of research and education. Through direct involve-ment in research, students will have unique learning and discovery opportunities in the areas of advanced semiconductor materials, nano-fabrication techniques, semiconductor physics, semi-conductor materials fabrication and device processing using state-of-the-art epitaxial growth, lithographic patterning, plasma etching, and advanced materials characterization. The project also encompasses development of strategic alliances with industry, which further enhances edu-cation and training opportunities for postdoctorals, graduate, and undergraduate students.***