Observation of coherent phonon-plasma coupled modes in wide gap semiconductors by transmission pump-probe measurements

Abstract

We have investigated coherent LO phonon properties in zinc-based II-VI widegap semiconductors, focusing on phonon-plasma coupled modes. By a careful treatment of the time evolution of the signals in ZnS, ZnSe, and ZnTe, we found a frequency upshift as the pump intensity increases. Using a classical coupled oscillator model, we have explained the pump intensity dependence of both the shift and the decay rates by a mixing of highly damped two-photon generated plasma. From the linear dependence between them we can estimate the photo-excited carrier mobilities, leading to a new powerful estimation method to measure the mobility.

The effect of ion irradiation on dephasing of coherent optical phonons in GaP

“…The prolonged dephasing time can be explained by considering the (one)electron-LO phonon coupling, 30,31 or plasmon-LO phonon coupling. 32,33 The decay rate 1/τ of the coherent LO phonon in defective GaP is given by the sum of the intrinsic anharmonic decay rate 1/τ anharmonic and the elastic scattering rate due to point defects 1/τ def ect . 1/τ anharmonic is given by Klemens formula γ 0 [1 + n(ω T A ) + n(ω LO )], 34,35 where γ 0 is an effective anharmonic constant, n(ω) is the phonon distribution function, and ω T A and ω LO are the frequencies of the TA and the LO phonons, respectively.…”