Abstract

In polar semiconductors like GaAs, the Fröhlich (polar) interaction between hot carriers and LO phonons is the dominant mechanism for carrier cooling. Because the coupling is strongest for small wave vector phonon modes, LO phonons with a wave vector <10⁶ cm⁻¹ are preferentially generated during the cooling. The result is a hot LO phonon distribution strongly peaked at small (but nonzero) wave vectors. The generation and decay of hot phonons are well understood in GaAs. However, heterojunction devices consisting of both binary semiconductors like GaAs and ternary alloys like Al_xGa_1-xAs are of considerable technological interest. The random substitution of Al and Ga on the crystal lattice can lead to important alloy disorder effects in the phonon spectrum. To understand how alloying affects the dynamics of electrons and phonons, we have performed subpicosecond pump-probe Raman scattering experiments^1,2 in Al_xGa_1-xAs.

© 1987 Optical Society of America