New photoacoustic mean for the determination of surface recombination velocity in piezocrystals

摘要

Abstract: A theoretical analysis is given of the surface recombination effect on laser generation of longitudinal acoustic pulses in piezocrystals. The acoustic pulses are excited through the inverse piezoelectric effect as a result of the electric fields induced by the spatial separation of photogenerated electrons and holes. Two regimes of dynamics of nonequilibrium electron-hole plasma are considered: the regime of independent motion of opposite-sign charge carriers and one of their ambipolar diffusion. The possibility of generating acoustic pulses with a duration equal to the surface recombination time is predicted. It is shown that the profile of pulse of longitudinal strain is essentially transformed as the surface recombination rate increases. Being based on these facts, a new photoacoustic mean is suggested to determine the high surface recombination velocity (s approximately equals 10$+6$/ cm/s) in piezocrystals. !16