Abstract

Within the first picoseconds after photogeneration, hot carriers in bulk GaAs relax predominantly by emitting optical phonons. The emitted phonons exist as a non-thermal phonon population until they decay anharmonically. Previously, the dynamics of the nonthermal phonon population was studied using time resolved anti-Stokes Raman spectroscopy [1]. For a carrier density larger than 10¹⁷ cm⁻³ the plasma frequency is comparable to the phonon frequency and coupling of the two excitations becomes non-negligible. In GaAs plasmon-phonon coupled modes have been observed in both single component plasmas (via doping)[2] and two component plasmas (via optical excitation)[3]. Due to the interaction of the phonons with the carrier plasma there have been no measurements of the phonon population dynamics for carrier densities larger than about 10¹⁷ cm⁻³. However, these non-equilibrium phonons play an important role in theories of hot carrier relaxation at high densities. In particular the existence of a large non-thermal phonon population and its reabsorption by carriers has been used to explain a reduction in the carrier energy loss rate[4].

© 1992 The Author(s)