Degenerate four-wave mixing experiments on GaN in the quasistationary regime

Haag, H.; Gilliot, P.; Lévy, R.; Hönerlage, B.; Briot, Olivier; Ruffenach-Clur, S.; Aulombard, Roger

doi:10.1063/1.123574

Cited by 14 publications

(5 citation statements)

References 7 publications

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“…l(a) have broadened and merged into one and the resulting induced transparency with increasing I,,c is about one third that at 10 K. The below-gap induced absorption is seen in Fig. l(d) to be approximately half that at 10 K. The decrease in the free exciton absorption with increasing I¢.c is attributed to many body effects, such as exciton screening by free carriers, causing a diminution of their oscillator strength.1 9 Lattice heating has been proposed as the origin of the below-gap induced absorption, 8 "'1 but is not consistent with observations in other nitride materials (see the following section). It's origin, therefore, is still not well understood.…”

Section: Resultsmentioning

confidence: 94%

“…8 Fig. l(c) shows the measured absorption changes with respect to the unpumped spectra for the pump densities given in Fig.…”

Section: Resultsmentioning

confidence: 96%

“…5 Picosecond FWM experiments have shown strong optical nonlinearities below 6 and at the band edge of GaN, 7 as have nanosecond FWM experiments. 8 However, much information is still unknown about the optical phenomena exhibited by these materials at the high carrier densities at which practical devices operate. Recently, nanosecond pump-probe transmission experiments have shown exciton saturation due to resonant and below resonance optical excitation of the excitonic transitions of GaN.…”

Section: Introductionmentioning

confidence: 99%

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Nondegenerate Optical Pump-Probe Spectroscopy of Highly Excited Group III Nitrides

et al. 1999

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We report the results of nondegenerate optical pump-probe absorption experiments performed on GaN and InGaN thin films and quantum wells under the conditions of strong optical band to band excitation. The evolution of the band edge in these materials was monitored as the number of photoexcited free carriers was increased beyond that required to achieve population inversion and observe stimulated emission. The band edge of InGaN is shown to exhibit markedly different high excitation behavior than that of GaN, explaining in part the reduction in stimulated emission threshold that typically accompanies the incorporation of indium into GaN to form InGaN. A comparison of the band edge absorption changes observed in pump-probe experiments to the gain spectra measured in variable-stripe gain experiments is also given.

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Section: Resultsmentioning

confidence: 94%

“…8 Fig. l(c) shows the measured absorption changes with respect to the unpumped spectra for the pump densities given in Fig.…”

Section: Resultsmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Nondegenerate Optical Pump-Probe Spectroscopy of Highly Excited Group III Nitrides

et al. 1999

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“…The exposure characteristics (EC) of diffraction efficiency (i.e. the diffraction efficiency as a function of excitation energy) were shown to be very informative if carrier generation mechanisms have to be characterized [6][7][8][9]. For relatively low efficiencies, the exposure characteristic of a diffracted signal follows a power law dependence [6,10].…”

Section: Transient Free Carrier Grating Characteristicsmentioning

confidence: 99%

Evaluation of photoelectric processes in photorefractive crystals via the exposure characteristics of light diffraction

Kadys

Gudelis²,

Sūdžius³

et al. 2004

J. Phys.: Condens. Matter

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We demonstrate a novel way to analyse carrier recombination and transport processes in photorefractive semiconductors via the exposure characteristics of light induced diffraction. The results of a picosecond four-wave mixing on free carrier gratings in semi-insulating GaAs crystals at various grating periods and modulation depths of a light interference pattern are discussed. The role of a deep-trap recharging in carrier diffusion and recombination is sensitively revealed through a feedback effect of a space-charge field to non-equilibrium carrier transport.

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“…In this study, we try to elucidate this reason by the viewpoint of carrier dynamics. The transient grating (TG) method which is one of third-order nonlinear spectroscopy, has been used for GaN to detect the nonlinear susceptibility [3], exciton dephasing time [4], time response of scattering [5], or quantum beat [6], etc. It is also a powerful tool to directly detect diffusion processes.…”

mentioning

confidence: 99%

Carrier Dynamics in InGaN/GaN SQW Structure Probed by the Transient Grating Method with Subpicosecond Pulsed Laser

Okamoto

Kaneta

Inoue

et al. 2001

phys. stat. sol. (b)

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Carrier dynamics in GaN and InGaN/GaN SQW structures were observed by using the transient grating (TG) method with sub-picosecond pulsed laser at room temperature. The diffusion coefficients (D) of photo-created carriers were estimated by the decay rate time of TG signals and the photoluminescence (PL) lifetime. It was found that D depends on the emission wavelength (In composition). The relationship between the emission efficiencies and carrier diffusion was considered in terms of the spatial inhomogeneity of In composition.Recently, InGaN/GaN-based light emitting diodes (LEDs) have been commercialized in ultraviolet (UV), blue, green, and amber spectral region [1,2]. In particular, the external quantum efficiency (h ext ) of about 20% is now achieved in blue (450 nm) LEDs. However, h ext values are still lower for LEDs out of this blue spectral range, but detailed reasons for the reduction of h ext have so far not been elucidated. In this study, we try to elucidate this reason by the viewpoint of carrier dynamics. The transient grating (TG) method which is one of third-order nonlinear spectroscopy, has been used for GaN to detect the nonlinear susceptibility [3], exciton dephasing time [4], time response of scattering [5], or quantum beat [6], etc. It is also a powerful tool to directly detect diffusion processes. By using this method, Haag et al. [7] have measured and reported the carrier diffusion in GaN. We observed the diffusion of heat energy generated by the nonradiative recombination of carriers in GaN and ZnSe by the TG method with nano-second pulsed laser [8,9]. In this work, we observed carrier diffusion in InGaN/GaN-based SQW structures in UV, blue, green, and amber spectral region by using the TG method with sub-picosecond pulsed laser.The samples used in this study were grown on a (0001) oriented sapphire (Al 2 O 3 ) substrate by a two-flow metalorganic chemical vapor deposition (MOCVD) technique [10]. The thickness of GaN bulk layer is 4 mm. GaN/InGaN SQW structure is composed of a GaN (1.5 mm), an n-GaN:Si (2.3 mm), an InGaN SQW (3 nm) and a GaN cap (5 nm) layer. LED structure of GaN/InGaN SQW is composed of GaN (30 nm), n-type 1 GaN : Si (5 mm), InGaN SQW (3 nm), p-type AlGaN : Mg (60 nm) and p-type GaN : Mg (150 nm).For the TG measurement, a mode-locked fiber laser and regenerative amplifier system (Clark) was used. The frequency doubled beam (388 nm) was used as pump beam. Pulse width, power, and repetition rate were 500 fs, 1 mW and 1 Hz, respectively. The pump beam was split into two coherence beams and crossed again in the sample with q = 30 and 120 . The modulation of carrier density (grating) is created in the sample by the interference pattern. The fundamental beam (775 nm) was used as a probe beam with the optical delay unit. The probe beam was partly diffracted, which was detected by a photomultiplier tube (Hamamatsu) and averaged with a boxcar integrator. For the time-resolved photoluminescence (TRPL) measurements, the frequency doubled beam of a mode-locked Ti : sapphire laser (Spec...

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Degenerate four-wave mixing experiments on GaN in the quasistationary regime

Cited by 14 publications

References 7 publications

Nondegenerate Optical Pump-Probe Spectroscopy of Highly Excited Group III Nitrides

Nondegenerate Optical Pump-Probe Spectroscopy of Highly Excited Group III Nitrides

Evaluation of photoelectric processes in photorefractive crystals via the exposure characteristics of light diffraction

Carrier Dynamics in InGaN/GaN SQW Structure Probed by the Transient Grating Method with Subpicosecond Pulsed Laser

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