Hot-carrier transport in diamond controlled by femtosecond laser pulses

Abstract

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. A hot-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.

Ultrashort-laser electron–hole plasma and intragap states in diamond

“…In such case, the A-band PL yield nonlinearity could continuously decrease versus fs-laser intensity, as observed through comparison of the intensity-dependent nonlinearities in this and our recent work [18] at rather similar experimental conditions. Meanwhile, even in this situation the difference in focusing NA = 0.25 [18] and 0.45 (this study) could introduce considerable difference in the density of excited carriers in their focal volumes and the resulting A-band photoluminescence yield through ultrafast lateral electron-hole plasma densitydependent ambipolar diffusion during the pumping 300fs laser pulses [19], which is not well-studied yet in diamond at high-excitation densities [20].…”

Excitons and fundamental transport properties of diamond under photo‐injection

“…Throughout this article, we focused on thermally and chemically equilibrated excitons and carriers. It should be noted that there is also rich physics at earlier times, such as nonequilibrium transport () and valley polarization () of hot carriers. Remaining challenges along this line include observing the dynamics of internal thermalization, pursuing the detailed nature of exciton transport by phonon wind, clarifying nonlinear kinetics of polyexcitons and electron–hole droplets, and so on.…”

Ultrafast Laser Processing of Diamond Materials: A Review

“…Quantum kinetic-type approaches, two temperature models and rate equations have been applied to account for all main relaxation processes [177][178][179]. In quantum-kinetic approach, the starting point is a Hamiltonian that describes the electron and the phonon subsystems and their coupling to first and second order in the atomic displacements using secondquantized formalism.…”