Hot-carrier transport in diamond controlled by femtosecond laser pulses

A laser-induced transient grating technique with femtosecond temporal resolution was used for the study of hot-carrier diffusion and anisotropy of an ambipolar diffusion coefficient in monocrystalline diamond. Ahot-carrier transport regime observed at temperatures below 200 K and excited carrier densities lower than 10(16) cm(-3) persist in the sample 20-30 ps after photoexcitation. Measured drift velocity of hot carriers was approximately 4-8 times higher compared to thermalized carriers. At low sample temperatures and excited carrier densities, the ambipolar diffusion coefficient was found to be anisotropic between < 100 > and < 110 > crystallographic directions. We demonstrated experimentally that the carrier energy distribution can be controlled on a sub-picosecond timescale by an additional laser pulse with photon energy below the width of a diamond band gap absorbed by the excited carrier system. Our experimental data were reproduced well by Monte Carlo simulations that confirm the presence of a hot-carrier diffusion regime in diamond.