The physical principles and application case studies of the novel diagnostic technique of laser infrared photothermal radiometry (PTR) of semiconductors are presented. Following superband gap optical excitation, the signal consists of two contributions, one due to the de-exciting carrier density (plasma wave) and another from direct absorption and heating of the lattice (thermal wave). Multiparameter Bts to frequency-domain amplitude and phase data have been developed to reliably measure recombination lifetime, tau surface recombination velocities (front and back surface), electronic, and thermal diffusivities. Applications case studies are presented, which demonstrate that lifetime measurements using PTR provide a most sensitive, convenient, and nonintrusive, remote industrial semiconductor metrology. The new metrology combines the features of several, laboratory and commercial techniques currently available for industrial wafer (substrate and process) characterization (e.g., thermoreflectance, microwave reflectance, and surface photovoltage). The technology is capable of being used as a sensitive control of ion implantation, contamination monitor during oxidation and wafer cleans, and photoexcited carrier recombination lifetime measurements.