Free carrier dynamics of InN nanorods investigated by time-resolved terahertz spectroscopy

Ahn, Hyeyoung; Chuang, Ching-Te; Ku, Yan; Pan, Ci‐Ling

doi:10.1063/1.3068172

Cited by 7 publications

(4 citation statements)

References 14 publications

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“…Evidently, biexponential decay behaviors of the samples represent two characteristic recombination channels involved in the recombination process. Combining previous studies 38,40 and analysis below, the fast decay is mainly attributed to rapid photocarrier capture by the surface traps, and the slow decay is mainly ascribed to nonradiative structural-defect-related recombination. The characteristic time τ 1 of fast decay for CdS nanobelts is measured as 21.4 ps; the value is consistent with that of 28 ps for CdS nanoparticles investigated by the optical-pump IR-probe technique.…”

supporting

confidence: 62%

“…On the other hand, revealed in parts a and b of Figure 4, the slow process does not show observable excitation intensity dependence, suggesting that the carrier recombination is mainly due to structural-defect-related nonradiative recombination and/or band-to-band recombination. 40 In this work, the origin of structural defects is attributed to the compositional disorder in ternary compound. The characteristic lifetime of slow process is 1000 ps for CdS nanobelts, while it is 894 ps for CdS 0.65 Se 0.35 nanobelts.…”

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confidence: 99%

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Defect Engineering in CdS_xSe_1–x Nanobelts: An Insight into Carrier Relaxation Dynamics via Optical Pump–Terahertz Probe Spectroscopy

Liu

Teoh

et al. 2012

J. Phys. Chem. C

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Defects in nanomaterials often induce dramatic changes in the photoelectrical properties of semiconducting II–VI compound nanomaterials. The relationship between defects and carrier dynamics is pivotal in material engineering for potential applications. A thorough understanding of the dynamics of defect-related free carrier depletion is particularly important for the fabrication and optimization of nano-optoelectronic devices. In this work, optical pump–terahertz probe spectroscopy was employed to investigate the carrier dynamics in CdS and Se-alloyed CdS nanobelts. The dynamics are dominated by the surface defect trapping in the case of CdS and structural-defect-related recombination for the Se-alloyed CdS. The conclusion is also supported by temperature-dependent photoluminescence spectroscopic studies. Our results indicate that congeneric element replacement is an effective approach for defect-distribution restructuring, which modifies the physical properties of nanomaterials through defect engineering.

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confidence: 62%

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confidence: 99%

Defect Engineering in CdS_xSe_1–x Nanobelts: An Insight into Carrier Relaxation Dynamics via Optical Pump–Terahertz Probe Spectroscopy

Liu

Teoh

et al. 2012

J. Phys. Chem. C

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“…The carrier densities in NRs were separately estimated from the timedomain THz spectroscopy experiment and were found to be about one order of magnitude higher than that of the InN epilayer. 15) The temperature-dependent PL peak energy of the InN epilayer in Fig. 2 exhibits an S-shape dependence and gradually redshifts with a further increase of temperature, following the temperature dependence described by Varshni's equation.…”

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confidence: 64%

Photoluminescence from InN Nanorod Arrays with a Critical Size

Ahn¹,

Liu²,

Chang³

et al. 2013

Appl. Phys. Express

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In this report, we investigated the rod size dependence of photoluminescence (PL) from vertically aligned indium nitride (InN) nanorod arrays grown on Si(111) substrates. Abnormal temperature dependence of the PL peak energy and the PL bandwidth was observed for InN nanorods with a critical diameter, which is of the same order of the surface electron accumulation layer (20 nm). Exceptionally large activation energy of the nanorods with the critical diameter implies that holes within these narrow nanorods need to surpass the band bending energy near the surface in order to recombine with electrons accumulated in the surface layer. #

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“…The dominant contribution of the BF effect to reflectivity is also observed for InN nanorod arrays which are grown at sample temperature of 520˚C on Si(111). 18,19 InN nanorod arrays consisted of nanorods of the diameter of 60 and 130 nm have higher background carrier density (~10 19 cm -3 ) than InN films which exceeds the density of photoexcited carriers at the current pump fluence 20 experience the strong BF effect and the transient reflectivity sharply increases as soon as the pump pulses arrive. The details of the carrier dynamics of InN nanostructure arrays will be discussed in the future publication.…”

Section: Ultrafast Optical Pump-and-probe Experimentsmentioning

confidence: 99%

Carrier dynamics of Mg-doped indium nitride

Ahn

Hong

Yang

et al. 2011

Ultrafast Phenomena in Semiconductors and Nanostructure Materials XV

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We report the carrier density dependence of carrier dynamics of Mg-doped InN (InN:Mg) films. Recently, we have demonstrated a significant enhancement of terahertz emission from InN:Mg, which is due to the temporal evolution of drift and diffusion currents depending on the background carrier density. We studied the details of carrier dynamics of InN:Mg which is crucial for the clarification of the terahertz emission mechanism by performing the time-resolved optical reflectivity measurement on InN:Mg films grown with different Mg-doping levels. Experimental analysis demonstrates that the initial sharp drop and recovery of reflectivity response of InN:Mg films are dominated by photocarrier-dependent bandgap renormalization and band filling processes, whereas the slow decay time constant (τ 2 ) of reflectivity of InN:Mg has the strong dependence on the background carrier density. As the carrier density decreases from that of undoped InN, τ 2 of InN:Mg continuously increases and reaches the maximum value at a critical value of ~1×10 18 cm −3 . Interestingly, the strongest terahertz radiation was observed at this carrier density and it keeps decreasing with the increase of carrier density. Intense terahertz radiation corresponds to the fast and large spatial separation of charged carrier density through diffusion and drift. Large spatial separation results in the longer decay time for charged carriers to reach equilibrium after strong emission of terahertz waves, and it explains the similar carrier density dependence of terahertz emission and τ 2 .

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Free carrier dynamics of InN nanorods investigated by time-resolved terahertz spectroscopy

Cited by 7 publications

References 14 publications

Defect Engineering in CdS_xSe_1–x Nanobelts: An Insight into Carrier Relaxation Dynamics via Optical Pump–Terahertz Probe Spectroscopy

Defect Engineering in CdS_xSe_1–x Nanobelts: An Insight into Carrier Relaxation Dynamics via Optical Pump–Terahertz Probe Spectroscopy

Photoluminescence from InN Nanorod Arrays with a Critical Size

Carrier dynamics of Mg-doped indium nitride

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Free carrier dynamics of InN nanorods investigated by time-resolved terahertz spectroscopy

Cited by 7 publications

References 14 publications

Defect Engineering in CdSxSe1–x Nanobelts: An Insight into Carrier Relaxation Dynamics via Optical Pump–Terahertz Probe Spectroscopy

Defect Engineering in CdSxSe1–x Nanobelts: An Insight into Carrier Relaxation Dynamics via Optical Pump–Terahertz Probe Spectroscopy

Photoluminescence from InN Nanorod Arrays with a Critical Size

Carrier dynamics of Mg-doped indium nitride

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Defect Engineering in CdS_xSe_1–x Nanobelts: An Insight into Carrier Relaxation Dynamics via Optical Pump–Terahertz Probe Spectroscopy

Defect Engineering in CdS_xSe_1–x Nanobelts: An Insight into Carrier Relaxation Dynamics via Optical Pump–Terahertz Probe Spectroscopy