Carrier dynamics and photoelectrical parameters in highly compensated sublimation grown 3C-SiC layers studied by time-resolved nonlinear optical techniques

Liaugaudas, Gediminas; Ščajev, Patrik; Jarašiūnas, K.

doi:10.1088/0268-1242/29/1/015004

Cited by 12 publications

(6 citation statements)

References 36 publications

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“…The latter indicates larger separation between the shallow localized tail states in S2. The temperature increase led to the suppression of decay tails due to activation of carriers from these tail (donor) states, as observed by DT in other compensated materials 44 , 45 .…”

Section: Resultsmentioning

confidence: 65%

Impact of dopant-induced band tails on optical spectra, charge carrier transport, and dynamics in single-crystal CdTe

Ščajev

Mekys

Subačius

et al. 2022

Sci Rep

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Cadmium telluride (CdTe) semiconductors are used in thin-film photovoltaics, detectors, and other optoelectronic applications. For all technologies, higher efficiency and sensitivity are achieved with reduced charge carrier recombination. In this study, we use state-of-the-art CdTe single crystals and electro-optical measurements to develop a detailed understanding of recombination rate dependence on excitation and temperature in CdTe. We study recombination and carrier dynamics in high-resistivity (undoped) and arsenic (As)-doped CdTe by employing absorption, the Hall effect, time-resolved photoluminescence, and pump-probe in the 80–600 K temperature range. We report extraordinarily long lifetimes (30 µs) at low temperatures in bulk undoped CdTe. Temperature dependencies of carrier density and mobility reveal ionization of the main acceptors and donors as well as dominant scattering by ionized impurities. We also distinguish different recombination defects. In particular, shallow AsTe and deep VCd−AsCd acceptors were responsible for p-type conductivity. AX donors were responsible for electron capture, while nonradiative recombination centers (VCd−AsTe, As2 precipitates), and native defects (VCd−TeCd) were found to be dominant in p-type and n-type CdTe, respectively. Bimolecular and surface recombination rate temperature dependencies were also revealed, with bimolecular coefficient T−3/2 temperature dependence and 170 meV effective surface barrier, leading to an increase in surface recombination velocity at high temperatures and excitations. The results of this study allowed us to conclude that enhanced crucible rotation growth of As-doped CdTe is advantageous to As activation, leading to longer lifetimes and larger mobilities and open-circuit voltages due to lower absorption and trapping.

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Section: Resultsmentioning

confidence: 65%

Impact of dopant-induced band tails on optical spectra, charge carrier transport, and dynamics in single-crystal CdTe

Ščajev

Mekys

Subačius

et al. 2022

Sci Rep

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“…We employ a light-induced transient grating (LITG) technique, which enables direct determination of τ and D values in a single experiment and in a contactless, nondestructive way . LITG has been used for similar measurements of many inorganic semiconductors, most recently in III-nitrides, , SiC, and diamond…”

Section: Introductionmentioning

confidence: 99%

Two Regimes of Carrier Diffusion in Vapor-Deposited Lead-Halide Perovskites

et al. 2017

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Metal halide perovskites are attractive materials for the realization of cheap and effective solar cells, thin film transistors, and light emitters. Carrier diffusion at high excitations, however, is poorly addressed in perovskites, even though it governs the diffusion length and determines the efficiency of photonic devices. To fully understand the dependence of diffusion length on carrier density, we performed direct and independent measurements of the carrier diffusion coefficient and recombination rate in several methylammonium lead-halide perovskite layers by applying the light-induced transient grating technique. We demonstrate the existence of two distinct carrier diffusion regimes within the density range of 1018–1020 cm–3. In the perovskite films of high compositional quality, diffusion is governed by a bandlike transport of free carriers. The diffusivity is high (0.28–0.7 cm2/s) in these samples, even at low carrier density, and further increases with excitation due to carrier degeneracy. The opposite scenario was observed in disordered perovskite layers, where diffusion is governed by hopping-like transport of localized carriers. The diffusion coefficient in latter layers is small (0.01–0.04 cm2/s at low densities) and increases with excitation due to local state filling and carrier delocalization. We show that carrier recombination can be well-described using the nonlinear radiative and nonradiative recombination coefficients that saturate with excitation due to phase space filling at high carrier densities. On the basis of these findings, we provide recommendations for the maximization of carrier diffusion length in different perovskites.

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“…However, in that case the observed lower D value can be explained by fast carrier trapping to boron hole traps (negatively charged before excitation). According to the methodology given in [28], D meas = D a0 (∆N-∆N trapped )/∆N, their density of 1.5 × 10 13 cm -3 was evaluated (see Fig. 1(b), full fit at ∆N < 10 15 cm -3 ).…”

Section: Excitation-dependent Carrier Diffusivity From Litgmentioning

confidence: 99%

Recombination and diffusion processes in electronic grade 4H silicon carbide

Ščajev¹,

Subačius²,

Jarašiūnas³

et al. 2019

physics

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Carrier dynamics in n-type 4H-SiC epilayers of varying thicknesses and low Z1/2 defect concentrations are investigated here in wide ranges of excess carrier density and temperature. Several techniques are employed to monitor carrier diffusion and recombination processes, including light induced transient grating (LITG), microwave photoconductance decay (MPCD) and free carrier absorption (FCA) using ps-laser pulses at 355 nm. The observed increase of the diffusion coefficient with the increasing excitation level is explained by the transition from the minority to the bipolar transport regime. Its subsequent decrease with even higher excitations is found to be governed by band-gap renormalization and degeneracy effects. The bulk lifetime, limited by hole traps at 0.19–0.24 eV above the valence band at lower excitations, was found to decrease from few microseconds to hundreds of nanoseconds during the transition regime from the minority to the bipolar transport. Our temperature-dependent measurements confirmed the trap activation energy and provided the approximate functional form of electron and hole lifetimes as τe = 340 × (T/300 K)3/2 ns and τh = 100 × (T/300 K)–1/2 ns, for the temperature T range 80–800 K. It was found to hold for 65 and 120 μm sample thicknesses, while the lifetimes were found to be twice shorter for the sample 35 μm thick.

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Carrier dynamics and photoelectrical parameters in highly compensated sublimation grown 3C-SiC layers studied by time-resolved nonlinear optical techniques

Cited by 12 publications

References 36 publications

Impact of dopant-induced band tails on optical spectra, charge carrier transport, and dynamics in single-crystal CdTe

Impact of dopant-induced band tails on optical spectra, charge carrier transport, and dynamics in single-crystal CdTe

Two Regimes of Carrier Diffusion in Vapor-Deposited Lead-Halide Perovskites

Recombination and diffusion processes in electronic grade 4H silicon carbide

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