Optical monitoring of nonequilibrium carrier diffusion in single crystalline CVD and HPHT diamonds under high optical excitation

Ščajev, Patrik; Malinauskas, T.; Lubys, L.; Ивакин, Е. В.; Nesládek, Miloš; Haenen, Ken; Jarašiūnas, K.

doi:10.1002/pssr.201105186

Cited by 19 publications

(22 citation statements)

References 13 publications

(23 reference statements)

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“…[8][9][10][11][12][13][14] However, the density of photoexcited carriers can strongly influence the measured diffusion coefficients. 8,13,14 Experiments on n-type semiconductors give a consistent result: D a is either an increasing or a flat function of photocarrier density. For instance, recent work on n-GaAs quantum wells has shown D a (or the related "ambipolar spin diffusion") to be increasing in lightly doped wells 15 and flat in nominally undoped wells.…”

Section: Introductionmentioning

confidence: 99%

Diffusion of degenerate minority carriers in a p-type semiconductor

Weber

Kittlaus

2013

Journal of Applied Physics

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We report ultrafast transient-grating experiments on heavily p-type InP at 15 K. Our measurement reveals the dynamics and diffusion of photoexcited electrons and holes as a function of their density n in the range 2 × 10 16 to 6 × 10 17 cm −3 . After the first few picoseconds the grating decays primarily due to ambipolar diffusion. While at low density we observe a regime in which the ambipolar diffusion is electron-dominated and increases rapidly with n, at high n it appears to saturate at 34 cm 2 /s. We present a simple calculation that reproduces the main results of our measurements as well as of previously published measurements that had shown diffusion to be a flat or decreasing function of n. By accounting for effect of density on charge susceptibility we show that, in p-type semiconductors, the regime we observe of increasing ambipolar diffusion is unique to heavy doping and low temperature, where both the holes and electrons are degenerate; in this regime the electronic and ambipolar diffusion are nearly equal. The saturation is identified as a crossover to ambipolar diffusion dominated by the majority carriers, the holes. At short times the transient-grating signal rises gradually. This rise reveals cooling of hot electrons and, at high photocarrier density, allows us to measure ambipolar diffusion of 110 cm 2 /s in the hot-carrier regime.

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Section: Introductionmentioning

confidence: 99%

Diffusion of degenerate minority carriers in a p-type semiconductor

Weber

Kittlaus

2013

Journal of Applied Physics

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“…Injection dependence of carrier diffusivity on the less-defective growth side and nucleation sides of undoped sample revealed dominance of many body effects [7] and an impact of grain boundaries, respectively. The thermal diffusivity, D th , was lower in case of smaller crystallites due to scattering on grain boundaries.…”

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confidence: 97%

“…4). A mobility decrease is due to bandgap renormalization and electron-hole scattering while its increase is due to electron-hole plasma degeneracy and screening of electron-hole scattering (the theoretical curve is taken from our previous work [7]). Hence, the impact of structural and point defects is practically insignificant on the growth side.…”

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confidence: 99%

“…The decay kinetics are decorated Injection dependencies of ambipolar diffusivity in the U-CVD sample on the growth and nucleation side with large and small crystallite sizes, respectively. Open points are data for undoped monocrystalline CVD diamond [7]. The solid curve was theoretically calculated for undoped diamond [7].…”

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confidence: 99%

“…Open points are data for undoped monocrystalline CVD diamond [7]. The solid curve was theoretically calculated for undoped diamond [7].…”

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confidence: 99%

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Crystallite size dependent carrier recombination rate and thermal diffusivity in undoped and boron doped CVD diamond layers

Ščajev

Наргелас

Jarašiūnas

et al. 2013

Physica Status Solidi (a)

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Carrier dynamics under interband carrier injection conditions (213 nm) was studied in undoped and boron-doped microcrystalline diamond layers with different grain size. The grain size, determined by scanning electron microscopy and electron backscattered diffraction, varied from 130 mm on the growth side to $1-2 mm on the nucleation side of a 1.0 mm-thick undoped layer. Carrier lifetimes measured by differential transmittivity (DT) technique varied from 1 to 4 ns on the growth side to $220 ps on the nucleation side. Also the carrier diffusivity was found higher on the growth side. The B-doped layer with 40 mm grain size at the growth side exhibited 380 ps carrier lifetime, which decreased to 130 ps on the nucleation side. Even shorter lifetimes ($100-200 ps and $10 ps, correspondingly) were revealed in this layer by differential reflectivity decay due to impact of subsurface defects. Therefore we conclude that the recombination rate in presence of large grains is dominated by bulk non-radiative traps, as diffusion time of carriers to reach grain boundaries is much longer (few ms). An impact of grain boundaries to recombination is expected in case of smaller grains. Thermal grating decay provided values of thermal diffusivity D th in the range of 12-6 cm 2 s À1 , respectively, on the growth and nucleation side of the layers, and its decrease with reduction of grain size was attributed to phonon scattering on grain boundaries.

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Nonequilibrium carrier dynamics in bulk HPHT diamond at two‐photon carrier generation

Ščajev

Gudelis

Ивакин³

et al. 2011

Physica Status Solidi (a)

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We demonstrate applicability of time‐resolved free‐carrier absorption and transient grating techniques for investigation of carrier recombination and diffusion features in a bulk diamond. Carrier injection into a 1 mm thick, IIa type high‐pressure high‐temperature grown layer was realized by two‐photon absorption of ∼5 ps laser pulse at 351 nm wavelength. Kinetics of differential transmission in 80–800 K range at various excess carrier densities provided carrier lifetimes of 360 ns at room temperature and their temperature dependences. A linear increase of carrier recombination rate with injection in 450–800 K range resulted in carrier lifetimes up to 1 ns and was fitted by effective coefficient B* = 2 × 10−11– 4 × 10−9 cm3/s. The latter process was attributed to a trap‐assisted Auger recombination (TAAR) with coefficient CTAAR = B*/NTrap and tentatively ascribed to nitrogen related traps. An ambipolar carrier mobility with its peak value of ∼1500 cm2/Vs at room temperature was measured by transient grating technique at ∼1.5 × 1015 cm−3 excess carrier density.

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Optical monitoring of nonequilibrium carrier diffusion in single crystalline CVD and HPHT diamonds under high optical excitation

Cited by 19 publications

References 13 publications

Diffusion of degenerate minority carriers in a p-type semiconductor

Diffusion of degenerate minority carriers in a p-type semiconductor

Crystallite size dependent carrier recombination rate and thermal diffusivity in undoped and boron doped CVD diamond layers

Nonequilibrium carrier dynamics in bulk HPHT diamond at two‐photon carrier generation

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