Enhanced Direct-Free-Hole Absorption in Picosecond Laser-Excited Germanium

梁忠義(Chung-Yee Leung)

Chinese Journal of Physics

18卷4期（1981 / 01 / 01）

158 - 171

英文

Direct-free-hole (DFH) transition between the subbranches of the valence band normally has negligible contribution in the absorption of light by semiconductor whose bandgap is smaller than the photon energy. However, in the interaction of germanium with intense picosecond neodymium laser pulses, the DFH absorption rate is enormously enhanced by the high density and high distribution temperature of the free carriers created in the semiconductor. It is shown that this process has an important role in the ultrafast optical response of photo-excited Ge. Adding the DFH mechanism to a theoretical model proposed recently for the generation and the temporal evolution of non-equilibrium electron-hole plasmas in Ge produces better agreement between experiment and theory.