Experimental research is carried out on the high-pressure and optical properties of intrinsic and defect states in semiconductors and their nanostructures. This includes studies of: vibrational properties -- especially phonon-phonon and electron-phonon interactions; localized electronic states in defective crystals and disordered systems; photostructural changes and metastable bonding; and high-pressure phase transitions. Students conduct Raman scattering, luminescence, and other visible/IR spectroscopies to probe these phenomena in bulk semiconductors and wide-gap oxides, III-V and II-VI heterostructures in layer or nanoparticle form, III-V-N alloys and chalcogen glasses. Diamond-anvil pressure cells applying ~0.1-0.5Mbar at room - and cryogenic-temperatures are used in many studies.