Time-Resolved Transient Grating Spectroscopy for Studies of Nonequilibrium Carrier Dynamics in Wide Band-Gap Semiconductors

Using interdisciplinary fields relevant to a highly excited semiconductor — nonequilibrium phenomena in high density plasma, light-induced changes of optical properties, and dynamic holography, we developed time-resolved four-wave mixing technique for monitoring the spatial and temporal carrier dynamics in wide band-gap semiconductors. This opened a new possibility to analyse fast electronic processes in a non-destructive “all-optical” way, i.e. without any electrical contacts. This technique allowed evaluation of recombination and transport processes and the determination of important carrier parameters which directly reveal the material quality: carrier lifetime, bipolar diffusion coefficients, surface recombination rate, nonlinear recombination rate, diffusion length, threshold of stimulated recombination. The recent experimental studies of differently grown group III-nitrides (heterostructures and free standing films) as well silicon carbide epilayers by nondegenerate picosecond four-wave mixing are presented.