Optical study of carrier diffusion and recombination in CVD diamond

Abstract

We report on the measurements of nonequilibrium carrier dynamics in monocrystalline diamond prepared by the chemical vapor deposition (CVD) technique. Nonlinearly excited laser-induced transient grating (LITG) and timeresolved photoluminescence (PL) were used for investigation of carrier diffusion and recombination. Diffusion constant was observed to be strongly dependent on the sample temperature and carrier density (D ¼ 2.5-35 cm 2 s À1 ) what was explained in terms of the density dependent carrier-carrier scattering. The new method based on the time-resolved PL was proposed for measuring the diffusion and recombination dynamics of excitons. The measured exciton lifetime t FE ¼ 700-800 ns was temperature independent between 100 and 295 K.

Hot-carrier transport in diamond controlled by femtosecond laser pulses

“…Due to the low diffraction efficiency by the thin grating produced by above-band gap excitation, diffusion at high carrier densities was investigated (10 16 -10 19 cm −3 ). Typical observed grating decay times with the grating period Λ = 2-5 μm are 5-500 ps and they depend on carrier density, sample temperature, and amount of impurities [21][22][23][24]. Dynamics of electrons from different conduction band valleys can possibly be observed by this experimental technique only when the intervalley scattering time is longer than the measured LITG dynamics.…”

“…For evaluation of the diffusion coefficient in a standard LITG experiment, diffraction efficiency dynamics is measured as a function of the grating period. Obtained exponential decay rates are associated with the diffusion coefficient and the square of the inverse grating period via relation 1/(2τ d ) = 1/τ r + 4π 2 D/Λ 2 [19,21]. Here, τ d is diffraction efficiency decay time and τ r is carrier recombination decay time.…”

“…There are several publications dealing with optical measurements of ambipolar diffusion in diamond using the LITG technique [21][22][23][24]. Due to the low diffraction efficiency by the thin grating produced by above-band gap excitation, diffusion at high carrier densities was investigated (10 16 -10 19 cm −3 ).…”

Features of free carrier and exciton recombination, diffusion, and photoluminescence in undoped and phosphorus-doped diamond layers

“…Here  R0 is the bulk trap related lifetime (we assumed it to be 800 ns as in bulk CVD diamonds [1,2]), B = B rad + B nonrad is the quadratic recombination coefficient (consisting from radiative, B rad , and nonradiative, B nonrad , parts (arising due to trap-assisted [29] or Coulomb(exciton)-enhanced Auger recombination [30,31])), and C FC is the free carrier Auger recombination coefficient [11].…”

“…Using 13% PL efficiency at 10 17 cm -3 carrier density in bulk 0.4 mm thick diamond [3] with R0 = 700 ns [1] bulk lifetime, and the determined B ex and C FC coefficients, exciton radiative lifetime of  REX = 860 ns was obtained. Fit of the experimental PL efficiency in Fig.…”