Temperature Dependence of Optical Properties of h-GaN Films Studied by Reflectivity and Ellipsometry

Siozade, Laure; Colard, Stéphane; Mihailovic, M.; Leymarie, J.; Vasson, A.; Grandjean, N.; Leroux, M.; Massies, J.

doi:10.1143/jjap.39.20

Cited by 41 publications

(24 citation statements)

References 30 publications

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“…The open circles are the second derivatives of the ε 1 data, while the solid and the dashed lines are the best fits to 7,16 However, the 3D nature near E 0 CP is usually mixed with excitonic transitions which had been observed by reflectivity study. 26 We therefore expect degenerated effect on our measured E 0 CP by mixture of the valance to conduction band transition and excitonic peaks. Accordingly pure 3D lineshape (n = 0.5) could not explain our data well for the E 0 CP.…”

Section: Resultsmentioning

confidence: 82%

Temperature dependent dielectric function and the E critical points of hexagonal GaN from 30 to 690 K

et al. 2014

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The complex dielectric function ɛ and the E0 excitonic and band-edge critical-point structures of hexagonal GaN are reported for temperatures from 30 to 690 K and energies from 0.74 to 6.42 eV, obtained by rotating-compensator spectroscopic ellipsometry on a 1.9 μm thick GaN film deposited on a c-plane (0001) sapphire substrate by molecular beam epitaxy. Direct inversion and B-splines in a multilayer-structure calculation were used to extract the optical properties of the film from the measured pseudodielectric function ⟨ɛ⟩. At low temperature sharp E0 excitonic and critical-point interband transitions are separately observed. Their temperature dependences were determined by fitting the data to the empirical Varshni relation and the phenomenological expression that contains the Bose-Einstein statistical factor.

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Section: Resultsmentioning

confidence: 82%

Temperature dependent dielectric function and the E critical points of hexagonal GaN from 30 to 690 K

et al. 2014

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“…The measured TL signals have two components; a spike-like positive (∆n > 0) component and a slowly-decaying negative (∆n < 0) component. From the relationship of (∂n/∂N) > 0 [10] and (∂n/∂T) < 0 [11] in GaN, we assigned the fast component and slow component to the convex lens effect of the carrier density change (∆N) and the concave lens effect of the temperature change (∆T), respectively. The signal intensities and decay times of the fast components represent the light-generated carrier density and the carrier recombination/diffusion processes, respectively.…”

Section: Methodsmentioning

confidence: 99%

Sub‐microscopic transient lens spectroscopy of InGaN/GaN quantum wells

Okamoto

Fujita

Kawakami

et al. 2003

Physica Status Solidi (b)

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Transient lens (TL) spectroscopy was developed with sub-micrometer spatial resolution to observe the temporal and special behavior of the nonradiative processes of carrier dynamics in InGaN/GaN quantum wells (QW). We have observed the carrier density dynamics and the thermal dynamics in the TL signals with a nanosecond pulsed laser. We have also observed TL and photoluminescence (PL) signals by using near-field scanning optical microscopy (NSOM), and find that both PL and TL images are correlated and exhibit submicron scale spatial inhomogeneity. . We have also succeeded in the direct observation of the nonradiative processes (thermalization, heat conduction [3] and carrier diffusion [4]) by using transient grating (TG) spectroscopy. Although nonradiative processes of carriers are very important in determining optical emission properties, only few investigations have so far been conducted to experimentally elucidate the nonradiative processes, primarily due to the difficult nature of such measurements. We expect that transient lens (TL) spectroscopy, which has been developed for the photochemistry research field [5,6], is also applicable for the direct observation of nonradiative carrier processes. The principle of TL spectroscopy, which is based on the third order nonlinear optical effect, is similar to TG spectroscopy, but the experimental configuration is much simpler and the spatial resolution is significantly improved. Recently, we have reported for the first time an investigation of the TL spectroscopy to experimentally observe nonradiative processes in GaN and InGaN/GaN materials [7]. In this work, we show results from TL spectroscopy measurements with micro or sub-micro spatial resolution, and observe the temporal and special behavior of nonradiative processes of carries in InGaN/GaN quantum wells.

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“…23 From these relationships, we assigned the fast and slow components to the convex lens effect of the ␦N and the concave lens effect of the ␦T, respectively. ␦N͑x , t͒ and ␦T͑x , t͒ are given by the following rate equations: where rad and nonrad are the radiative and nonradiative recombination lifetimes of carriers, D and D th are the diffusion coefficient of carriers and the thermal diffusivity of the material, Q, and C p are the generated heat from unit density of carriers, material density and the heat capacity of material, respectively.…”

Section: ͑1͒mentioning

confidence: 99%

Near-field scanning optical microscopic transient lens for carrier dynamics study in InGaN∕GaN

Okamoto¹,

Scherer²,

Kawakami³

2005

Applied Physics Letters

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Time-resolved microscopic transient lens ͑TR-M-TL͒ and near-field scanning optical microscopic transient lens ͑NSOM-TL͒ were performed to reveal temporal and spatial behavior of carrier dynamics in InGaN/ GaN quantum wells. The carrier and thermal dynamics were observed through the time profile of the TR-M-TL signal. Also, NSOM-photoluminescence and NSOM-TL images were observed at the same time. By comparing these two images, both radiative and nonradiative recombination centers in InGaN active layer were unambiguously discriminated with submicrometer scale. Such nonradiative carrier dynamics has been difficult to observe by conventional techniques in spite of its importance.

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Temperature Dependence of Optical Properties of h-GaN Films Studied by Reflectivity and Ellipsometry

Cited by 41 publications

References 30 publications

Temperature dependent dielectric function and the E critical points of hexagonal GaN from 30 to 690 K

Temperature dependent dielectric function and the E critical points of hexagonal GaN from 30 to 690 K

Sub‐microscopic transient lens spectroscopy of InGaN/GaN quantum wells

Near-field scanning optical microscopic transient lens for carrier dynamics study in InGaN∕GaN

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