Composition and temperature dependent optical properties of AlxGa1-xN alloy by spectroscopic ellipsometry

Liu, Yao; Li, Qing Xuan; Wan, Ling; Küçükgök, Bahadir; Ghafari, Ehsan; Ferguson, Ian T.; Zhang, Xiong; Wang, Shuchang; Feng, Zhe Chuan; Lü, Na

doi:10.1016/j.apsusc.2017.01.309

Cited by 39 publications

(18 citation statements)

References 35 publications

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“…The bandgap decreases with the rise of temperature and is exhibited in Figure 10, which is in good agreement with Equation (6). The value of bandgap reduces from 3.328 eV to 3.083 eV in the temperature range of 300-850 K. The decrease of bandgap with increasing temperature is generally contributed to two factors: (i) the lattice thermal expansion and (ii) the change of the acoustic and optic phonons involved electron-phonon interactions [44,47,48]. .…”

Section: Study On Variable Temperature Sesupporting

confidence: 73%

Effects of Thermal Annealing on Optical Properties of Be-Implanted GaN Thin Films by Spectroscopic Ellipsometry

et al. 2020

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Wide bandgap III-V compounds are the key materials for the fabrication of short-wavelength optical devices and have important applications in optical displays, optical storage devices and optical communication systems. Herein, the variable-angle spectroscopic ellipsometry (SE) measurements are performed to investigate the thickness and optical properties of beryllium-implanted gallium nitride thin films that have been deposited on (0001) sapphire substrates by using low-pressure metalorganic chemical vapor deposition (LPMOCVD). The film layer details are described by using Parametric Semiconductor oscillators and Gaussian oscillators in the wavelength range of 200–1600 nm. The thickness, refractive indices and extinction coefficients of the Be-implanted films are determined at room temperature. Analysis of the absorption coefficient shows that the optical absorption edge of Be-implanted films changes from 3.328 eV to 3.083 eV in the temperature range of 300–850 K. With the variable temperature, Eg is demonstrated to follow the formula of Varshni. A dual-beam ultraviolet–visible spectrophotometer (UV–VIS) is used to study the crystal quality of samples, indicating that the quality of rapid thermal annealing (RTA) sample is better than that unannealed sample. By transport of ions in matter (TRIM) simulation and SE fitting the depths of Be implanted gallium nitride (GaN) films are estimated and in good agreement. The surface and cross-section morphologies are characterized by atomic force microscopy (AFM) and scanning electron microscope (SEM), respectively. The surface morphologies and thickness measurements of the samples show that RTA can improve crystal quality, while increasing the thickness of the surface roughness layer due to partial surface decomposition in the process of thermal annealing.

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Section: Study On Variable Temperature Sesupporting

confidence: 73%

Effects of Thermal Annealing on Optical Properties of Be-Implanted GaN Thin Films by Spectroscopic Ellipsometry

et al. 2020

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“…In our analyses, we have considered an interface region with silicate (SiO x ), which is observed clearly in the interface by high-resolution transmission electron microscope (HR-TEM), as shown in Figure 9. The surface roughness was described by Bruggeman effective medium approximation (EMA) [52,53]. The fitting structural model were constructed as silicon substrate/interface layer/HfO 2 layer/surface roughness.…”

Section: The Variable Angle Spectroscopic Ellipsometry (Vase)mentioning

confidence: 99%

Investigation of HfO2 Thin Films on Si by X-ray Photoelectron Spectroscopy, Rutherford Backscattering, Grazing Incidence X-ray Diffraction and Variable Angle Spectroscopic Ellipsometry

Luo

Yang

et al. 2018

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Hafnium oxide (HfO 2) thin films have been made by atomic vapor deposition (AVD) onto Si substrates under different growth temperature and oxygen flow. The effect of different growth conditions on the structure and optical characteristics of deposited HfO 2 film has been studied using X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), grazing incidence X-ray diffraction (GIXRD) and variable angle spectroscopic ellipsometry (VASE). The XPS measurements and analyses revealed the insufficient chemical reaction at the lower oxygen flow rate and the film quality improved at higher oxygen flow rate. Via GIXRD, it was found that the HfO 2 films on Si were amorphous in nature, as deposited at lower deposition temperature, while being polycrystalline at higher deposition temperature. The structural phase changes from interface to surface were demonstrated. The values of optical constants and bandgaps and their variations with the growth conditions were determined accurately from VASE and XPS. All analyses indicate that appropriate substrate temperature and oxygen flow are essential to achieve high quality of the AVD-grown HfO 2 films.

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“…The bandgap of the five samples is also calculated here. The optical absorption coefficient α is extracted from SE fitting results, and then the bandgap E g is calculated based on the formula below [39]:…”

Section: Resultsmentioning

confidence: 99%

Influence of Dislocations on the Refractive Index of AlN by Nanoscale Strain Field

et al. 2019

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The refractive index of AlN has a direct influence on AlGaN-based deep ultraviolet optoelectronic devices, such as the external quantum efficiency of light-emitting devices. Revealing the dependence of the refractive index of AlN on the threading dislocations is meaningful since high-density threading dislocations usually exist in AlN. In this paper, the effect of different dislocation densities on the refractive index of AlN is investigated. With the increase of dislocation densities from 4.24 × 10 8 to 3.48 × 10 9 cm − 2 , the refractive index of AlN decreases from 2.2508 to 2.2102 at 280 nm. Further study demonstrates that the nanoscale strain field around dislocations changes the propagation of light and thus decreases the refractive index of AlN. This study will be beneficial to the design of optoelectronic devices and thus realizing high-performance deep ultraviolet optoelectronic devices. Electronic supplementary material The online version of this article (10.1186/s11671-019-3018-7) contains supplementary material, which is available to authorized users.

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Composition and temperature dependent optical properties of AlxGa1-xN alloy by spectroscopic ellipsometry

Cited by 39 publications

References 35 publications

Effects of Thermal Annealing on Optical Properties of Be-Implanted GaN Thin Films by Spectroscopic Ellipsometry

Effects of Thermal Annealing on Optical Properties of Be-Implanted GaN Thin Films by Spectroscopic Ellipsometry

Investigation of HfO2 Thin Films on Si by X-ray Photoelectron Spectroscopy, Rutherford Backscattering, Grazing Incidence X-ray Diffraction and Variable Angle Spectroscopic Ellipsometry

Influence of Dislocations on the Refractive Index of AlN by Nanoscale Strain Field

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