Acoustic Phonon Generation in the Picosecond Dynamics of Dense Electron-Hole Plasmas in InGaAsP Films

Abstract

In spite of the extensive use of semiconductor alloys of InGaAsP in lasers, LEDs, and photodetectors, relatively little work relating to the ultrafast dynamics of photoexcited carriers has been reported. It will become increasingly important to understand the dynamics of free carriers in these materials when they become a material for integrated optoelectronic devices. In the present contribution, the dynamics of dense electron-hole plasmas created by ultrashort-pulse optical excitation of InGaAsP films is examined by probing transient transmission and reflection. Both the transient transmission and reflection data show an oscillation superimposed on a monotonically changing response. Similar oscillations have been reported by THOMSEN, et al[1] in a study of the dynamics of films of a — As₂Te₃ and cispolyacetylene photoexcited by ultrashort optical pulses. They have shown that the oscillations are due to coherent acoustic phonons generated in the relaxation of the hot, optically excited carriers. In the present work, the oscillatory behavior is reported and analyzed for films of InGaAsP and GaAs.