Characteristics Of Terahertz Wave Emissions Under The Coexistence Of Different Sub-Picosecond Transient Phenomena In Gaas Epitaxial Films

We report on the characteristics of the terahertz waveform originating from both the nonequilibrium transport of photogenerated carriers and the longitudinal optical phonon-plasmon coupled mode in GaAs epitaxial structures having a built-in electric field. The terahertz waveforms at different pump fluences were analyzed by an equation for the coherent oscillations of plasmons and phonons in addition to a Monte Carlo simulation. We clearly distinguished the contributions of two transient phenomena to the terahertz waveform, which enables us to evaluate the relationship between various physical properties and the terahertz waveform. Based on the analysis, the sample structure dependence was discussed.