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The long-range crystallographic order and anisotropy in β-(AlxGa1−x)2O3 (x = 0.0, 0.06, 0.11, 0.17, 0.26) crystals, prepared by optical floating zone method with different Al composition, is systematically studied by spatial correlation model and using an angle-resolved polarized Raman spectroscopy. Alloying with aluminum is seen as causing Raman peaks to blue shift while their full widths at half maxima broadened. As x increased, the correlation length (CL) of the Raman modes decreased. By changing x, the CL is more strongly affected for low-frequency phonons than the modes in the high-frequency region. For each Raman mode, the CL is decreased by increasing temperature. The results of angle-resolved polarized Raman spectroscopy have revealed that the intensities of β-(AlxGa1−x)2O3 peaks are highly polarization dependent, with significant effects on the anisotropy with alloying. As the Al composition increased, the anisotropy of Raman tensor elements was enhanced for the two strongest phonon modes in the low-frequency range, while the anisotropy of the sharpest Raman phonon modes in the high-frequency region decreased. Our comprehensive study has provided meaningful results for comprehending the long-range orderliness and anisotropy in technologically important β-(AlxGa1−x)2O3 crystals.

We have demonstrated a record short wavelength lasing at 244.63 nm with TE dominant polarization from GaN quantum wells (QWs) at room temperature (RT). The optical threshold of 310 kW/cm2 is compar...

We present a detailed study on the crystal structure of 0.10 mol% Ta-doped β-Ga2O3 crystals before and after annealing treatment in air by high-resolution X-ray diffraction and Raman spectroscopy, as well as the detection of point defects through the variation of photoluminescence excitation (PLE) and photoluminescence (PL) with temperature. Based on the experimental data, the band diagram of the 0.10 mol% Ta-doped β-Ga2O3 crystal is constructed. The crystal quality of the 0.10 mol% Ta-doped β-Ga2O3 crystal was improved after annealing treatment. The PL spectra exhibited two ultraviolet emission bands (UV ∼3.59 eV, UV′ ∼3.22 eV) and a blue emission band (BB ∼2.73 eV) , which are ascribed to the recombination of self-trapped excitons at the trigonal OI and OII sites and gallium vacancies in the (2−) charge state (tetrahedral site), respectively. The work function of the 0.10 mol% Ta-doped β-Ga2O3 crystal increased from 5.28 eV to 5.38 eV as a result of annealing treatment.

The optical properties of nonpolar AlGaN multiple quantum wells (MQWs) emitting at 280 nm were investigated intensively using temperature-dependent and time-resolved photoluminescence spectra associated with the characterization of structural properties. The densities of superficial pits and basal-plane stacking faults (BSFs) were reduced by 33.8% and 35.9%, respectively, for nonpolar AlGaN MQWs due to the carefully optimized dual nitridation. It was found that the nonpolar MQWs emission can be significantly improved by reducing the BSFs density as the BSFs emission was the main competing channels. Moreover, an internal quantum efficiency of 39% for nonpolar Al0.43Ga0.57N MQWs at emission wavelength of 279 nm was achieved even the full width at half maximum values of X-ray rocking curves were 0.565° for c-direction and 0.797° for m-direction. This fact means that a highly efficient deep ultraviolet light sources can be expected by means of nonpolar AlGaN due to the elimination of quantum confined Stark effect induced the decrease in radiative lifetime.

Exciton localization phenomena are considered here to comprehend the high internal quantum efficiency in InGaN/GaN multiple-quantum-well structures having discrete quantum dots (QDs) prepared by metal–organic-chemical-vapor deposition method on c-sapphire substrates. Spectroscopic results from the variable-temperature steady-state-photoluminescence and time-resolved photoluminescence (TRPL) are investigated. While the exciton localization is enhanced by strong localized states within the InGaN/GaN QDs–the impact of free carrier recombination cannot be ignored. The observed non-exponential decay in TRPL measurements is explained using a model by meticulously including localized exciton, non-radiative and free carrier recombination rates. A new method is proposed to calculate the internal quantum efficiency, which is supplementary to the traditional approach based on temperature-dependent photoluminescence measurement.

A systematic investigation is reported to comprehend the atomic and crystal structure of several thin ZnGaO films grown by metal organic chemical vapor deposition method using different flow rates of diethylzinc (DEZn) while keeping triethylgallium and oxygen flow rates constant. The x-ray absorption fine structure analysis has indicated that the local structure of Ga absorbing atom is close to that of β-Ga2O3 at a lower DEZn flow rate of 30 sccm and transforming to ZnGa2O4 structure at higher 60 sccm. There is a certain proportion of Ga ions that occupies the tetrahedral sites. The ratios of tetrahedral and octahedral Ga species (Ga(t)/Ga(o)) are found to be within 5.5–8.8%. The x-ray diffraction patterns showed the crystal structure of ZnGaO films gradually evolving from monoclinic to cubic phase with an increase of DEZn flow rates from 30 sccm to 60 sccm. One film prepared at 40 sccm displays the best crystalline quality and the other grown at 50 sccm exhibits excellent smooth surface having the lowest root mean square value with a roughness of 0.42 nm. The correlation between atomic and crystal structure and the growth is helpful to understand the formation of single-crystalline ZnGa2O4 and its physical mechanism.

A series of Ga2O3 films grown on sapphire substrate by pulsed laser deposition with different growth temperature (400–1000 °C) and different thickness (69–332 nm) were studied by X-ray diffraction, optical transmittance and spectroscopic ellipsometry. The phase was transformed from amorphous to polycrystalline β-Ga2O3 structure with increasing growth temperature. Refractive indexes increase with increasing thickness or growth temperature of the films in the transparent area, where the effect of film thickness is much more significant than that of growth temperature. The Urbach tail observed in absorption edge by ellipsometry combined with the transmittance spectra and the XRD intensities illustrate that higher growth temperature or thicker thickness can improve the crystal quality of films. The band gap of Ga2O3 films decrease with increasing growth film thickness and elevated experimental temperature (25–600 °C), and the quantitative analysis of temperature-dependent band gap was conducted by using the Varshni equation.

Comprehensive structural, electrical and optical studies are performed on a series of gallium oxide (Ga2O3) ultrathin films grown on sapphire with different growth temperatures (400–1000 °C) by pulsed laser deposition, via X-ray absorption spectroscopy (XAS), Raman scattering (RS) and X-ray photoelectron spectroscopy (XPS). For samples grown at different temperatures, the XAS results showed the coordination numbers of the materials varying, while their bond lengths remained nearly similar value. The RS revealed a low frequency vibration translation tetrahedral-octahedral mode (202 cm−1) of GaO4 and a mid-frequency deformation octahedral mode (346 cm−1) of GaO6 for films grown at higher temperatures. XPS analyses suggested the surface of samples composed of Ga O bonds with binding energy decreasing as the growth temperature increased. The β-Ga2O3/sapphire heterojunction is identified with the staggered-gap (type II) structure, and the valence-band offset (VBO) is found between (−0.52)–(−0.74) eV while conduction-band offset (CBO) from (−2.32)–(−3.32) eV. The band gap of the β-Ga2O3 was deduced from the energy loss signals for O 1s photoelectrons. With the increase of the growth temperature, the band gap increases and both the VBO and CBO decrease. The identification of band alignment for heterojunction may facilitate interests in designing advanced opto-electronic devices.

High-quality ZnCr2O4 (ZCO) thin films were epitaxially grown on economical c-sapphire substrates by pulsed laser deposition (PLD) for the first time, using a ZCO ceramic target and various deposition oxygen pressures. X-ray diffraction results revealed that the as-grown ZCO films consisted of a single spinel phase, and exhibited out-of-plane and in-plane orientations with respect to the c-sapphire substrate of ZCO (1 1 1)||Al2O3 (0 0 0 1) and ZCO [0 1 −1]||Al2O3 [1 −1 0], respectively. Due to domain matching with a tiny misfit of 0.015%, high-quality epitaxy of (1 1 1)-ZCO on c-sapphire was achieved with typical (2 2 2) rocking-curve half width of ∼0.07° and φ-scan half width of ∼1.85°. Moreover, the films exhibited very smooth surface with a minimum root-mean-square roughness of 0.585 nm. As the deposition oxygen pressure was increased, the atomic ratio of Zn/Cr in the ZCO films was found to increase linearly from 0.316 to 0.585, while the bandgap of the ZCO films increased simultaneously from 3.61 eV to 3.87 eV. The widening of bandgap was attributed to the enhancement of cations-anions interaction and reduction of oxygen vacancies with increasing deposition oxygen pressure. Our work provides a feasible and economical solution for the epitaxial growth of high-quality ZCO films, based on which fundamental properties and technological applications of ZCO can be further explored.

InSb thin films were grown on GaAs substrates by metal organic chemical vapor deposition (MOCVD) and investigated by temperature-dependent spectroscopic ellipsometry (TD-SE). The refractive index, extinction coefficient, and dielectric function of the InSb films were extracted. The variation of critical point energies (E1, E1+Δ1, E2, $$ {E}_1^{\hbox{'}} $$ ) related to the excited state transitions of InSb and the second energy derivatives of the dielectric function at different temperatures showed that the InSb thin film had high electrical and optical stability at the evaluated temperatures. TD-SE analysis revealed a temperature range suitable for the use of InSb/GaAs-based devices. Beyond 250°C, InSb was heavily oxidized to form a thin In-O layer, causing a pronounced change in the optical constants. The results indicated that optimized InSb thin films grown on GaAs by MOCVD possess good optical and structural properties.

The effects of the modulation in the NH3 flow duty-ratio in a three-way pulsed-flow epitaxial growth process on the structural and optical properties of non-polar a-plane Al0.34Ga0.66N epi-layers were studied intensively. It was revealed that the typical pyramidal defects originated from the anisotropy in growth rate could be evidently reduced with an optimized NH3 flow duty-ratio. In fact, the root-mean-square value determined with atomic force microscope was decreased from 12.8 to 3.1 nm when the NH3 flow duty-ratio was increased from 0 to 0.57. Moreover, the LO-phonon-assisted exciton emission observed in the photoluminescence (PL) spectrum was remarkably suppressed, and the linewidth of the near band edge PL emission peak was decreased by 47%, implying the significantly enhanced optical properties of the non-polar a-plane Al0.34Ga0.66N epi-layer.

Experimental and theoretical investigations are reported to comprehend the structural and lattice dynamical properties of high quality Bridgman grown zb Zn1-xMnxTe (x ≤ 0.15) crystals. Our detailed far-infrared reflectivity and Raman scattering measurements ascertained atypical “intermediate-phonon-mode” behavior for the alloys. Besides perceiving ZnTe- and zb MnTe-like LO and TO phonons, a weak Mn alloy-disorder mode near ∼205 cm−1 is observed. A classical “Drude-Lorentz” model is used for evaluating the dielectric tensors of ternary alloys to simulate composition dependent reflectivity spectra – providing results in good agreement with the experimental data at near normal incidence. Lattice relaxation effects around MnZn and ZnMn from the synchrotron radiation extended x-ray absorption experiments are meticulously incorporated to help construct the perturbation models for simulating impurity modes using a realistic rigid-ion-model in the frame work of an average t-matrix Greens function theory – reconfirming on much firmer ground – the observed intermediate phonon mode behavior.

As capture traps, Fe impurities were intentionally incorporated into beta-gallium oxide (β-Ga2O3) crystals to compensate for unintentional n-type conductivity for applications of semi-insulated single-crystal substrates with high-performances. The systematic investigations are performed to comprehend the influence of the Fe addition on the structural, optical, electronic properties of the β-Ga2O3 crystal, and the annealing effect by using a combination of multi-disciplinary techniques. The Fe-doped β-Ga2O3 crystal exhibits a good single-crystal phase and a high optical transmittance from 400 nm to 2000 nm from the measurements of high-resolution X-ray diffraction and optical transmission spectroscopies. Raman scattering spectra revealed that the high-frequency phonon modes which belong to the stretching and bending of tetrahedron were significantly inhibited by the Fe addition to the β-Ga2O3 crystal. EPR results discovered that the presence of Fe3+ ions preferentially in the octahedral over the tetrahedral sites of the monoclinic structure. After an annealing treatment, the crystalline quality was improved and the oxygen vacancies were reduced. The absorption edge redshifted and the transmittance decreased slightly. In particular, it was discovered that the position of the Fermi level is deviated towards the valence band and the total number of spins of Fe3+ ions was halved from 5.32 × 1014 to 2.86 × 1014 spins/mm3. The annealing treatment not only improved the crystal quality, but also activated irons trap centers and further decreased the conductivity.

Systematic investigations are performed to understand the temperature-dependent optical properties of graphene on Si and SiO2/Si substrates by using a variable angle spectroscopic ellipsometry. The optical constants of graphene have revealed changes with the substrate and temperature. While the optical refractive index (n) of monolayer graphene on Si exhibited clear anomalous dispersions in the visible and near-infrared region (400–1200 nm), the modification is moderate for graphene on SiO2/Si substrate. Two graphene sheets have shown a pronounced absorption in the ultraviolet region with peak position related to the Van Hove singularity in the density of states. By increasing the temperature from 300 K to 500 K, for monolayer graphene on Si, the n value is gradually increased while k decreased. However, the optical constants [n, k] of monolayer graphene on SiO2/Si exhibited unpredictable wave variations. In the wavelength range of 400–1200 nm, an experiential formula of a like-Sellmeier equation is found well suited for describing the dispersions of graphene on Si and SiO2/Si substrates.

We report on the structural and optical properties of polar gallium nitride on c-plane sapphire substrates and semi-polar (11–22) GaN films on m-plane sapphire substrates by metalorganic chemical vapor deposition. Polar GaN on c-plane sapphire and semi-polar GaN on m-plane sapphire both show good crystal quality, luminescence, absorption, and Raman characteristics. GaN on c-place sapphire shows a high crystal quality as compared to GaN on m-plane sapphire. Surface roughness of polar GaN is lesser than semi-polar GaN. The biaxial structural stress in GaN switches from compressive to tensile as the temperature is increased. This stress-switch temperature is higher in GaN/c-plane than GaN/m-plane. GaN in polar and semi-polar orientation shows ultraviolet emissions but yellow-emissions are only observed in GaN/c-plane sapphire. Raman spectroscopy-related oscillations show systematic variations with temperature in both GaN configurations (polar and semi-polar). This work provides a framework of characterizations for GaN with different crystal polarities. It contributes towards identifying suitable crystal growth mechanisms based on the application and requirements for doping (In, Al, etc), crystal quality, emission, absorption, and photonic oscillations.

AlN thin films grown on different face sapphire substrates by metalorganic chemical vapor deposition were studied comprehensively by a variety of techniques including high resolution X-ray diffraction (HR-XRD), X-ray photoelectron spectroscopy (XPS), Raman scattering (RS) and theoretical calculations. Our results showed that substrate orientation has a drastic effect on the initial growth of AlN. The AlN films showed dominant semipolar (101) orientation but with slightly weaker individual features. Optical reflectance measurements confirmed that AlN films grown on different surface orientation sapphire substrates at the same time possessed different film thicknesses. It was found that the surface orientation also has a major influence on the dislocation density, crystallite size, and surface oxygen incorporation. Raman line width exhibited good correlation with XPS measurements. The combined analyses led to a better understanding of the variation in the quality of the AlN films grown on different faces of sapphires.

This paper reports the photoluminescence (PL) properties of InGaN/GaN multiple quantum well (MQW) light-emitting diodes grown on silicon substrates which were designed with different tensile stress controlling architecture like periodic Si δ-doping to the n-type GaN layer or inserting InGaN/AlGaN layer for investigating the strain-controlled recombination mechanism in the system. PL results turned out that tensile stress released samples had better PL performances as their external quantum efficiencies increased to 17%, 7 times larger than the one of regular sample. Detail analysis confirmed they had smaller nonradiative recombination rates ((2.5~2.8)×10−2 s−1 compared to (3.6~4.7)× 10−2 s−1), which was associated with the better crystalline quality and absence of dislocations or cracks. Furthermore, their radiative recombination rates were found more stable and were much higher ((5.7~5.8) ×10−3 s−1 compared to [9~7] ×10−4 s−1) at room temperature. This was ascribed to the suppression of shallow localized states on MQW interfaces, leaving the deep radiative localization centers inside InGaN layers dominating the radiative recombination.

A series of ultrathin InSb films grown on GaAs by low-pressure metalorganic chemical vapor deposition with different V/III ratios were investigated thoroughly using spectroscopic ellipsometry (SE), X-ray diffraction, and synchrotron radiation X-ray absorption spectroscopy. The results predicted that InSb films on GaAs grown under too high or too low V/III ratios are with poor quality, while those grown with proper V/III ratios of 4.20–4.78 possess the high crystalline quality. The temperature-dependent SE (20–300°C) and simulation showed smooth variations of SE spectra, optical constants (n, k, e1, and ε2), and critical energy points (E1, E1+Δ1, E′0, E2, and E′1) for InSb film when temperature increased from 20°C to 250°C, while at 300°C, large changes appeared. Our study revealed the oxidation of about two atomic layers and the formation of an indium-oxide (InO) layer of ∼5.4 nm. This indicates the high temperature limitation for the use of InSb/GaAs materials, up to 250°C.

An internal quantum efficiency (IQE) as high as 39% was achieved with the nonpolar a-plane AlGaN-based multiple quantum wells (MQWs) grown on the r-plane sapphire substrate with metal organic chemical vapor deposition technology. Evident fourth order X-ray diffraction satellite peak and intense MQW-related exciton emission peak at a wavelength of 279.2 nm were observed, implying the successful growth of high quality nonpolar a-plane AlGaN-based MQWs. It was found that the employment of the trimethyl-aluminum (TMAl) flow duty-ratio modulation method played a crucial role in the epitaxial growth of the nonpolar a-plane AlGaN MQWs with sharp heterointerfaces and high IQE. Moreover, the unambiguous absence of the blue-shift in the MQWs-related exciton emission peak was verified in spite of the increase in the excitation power during the measurement of the excitation power-modulated photoluminescence spectra, indicating a complete elimination of the quantum confined Stark effect in the nonpolar AlGaN-based MQWs.

Comprehensive experimental and theoretical studies are reported to assess the vibrational and structural properties of 3C-SiC/Si (001) epilayers grown by chemical vapor deposition in a vertical reactor configuration. While the phonon features are evaluated using high resolution infrared reflectance (IRR) and Raman scattering spectroscopy (RSS) – the local inter-atomic structure is appraised by synchrotron radiation extended x-ray absorption fine structure (SR-EXAFS) method. Unlike others, our RSS results in the near backscattering geometry revealed markedly indistinctive longitudinal- and transverse-optical phonons in 3C-SiC epifilms of thickness d

Six CdTe thin epifilms were prepared by using molecular beam epitaxy on ion beam cleaned InSb (001) substrates with Tsub temperatures ranging from 25 to 250 °C. Thickness dependent vibrational and structural characteristics are meticulously examined by far-infrared reflectivity (FIR) and high-resolution synchrotron extended x-ray absorption spectroscopy (HR-XAS), respectively. The FIR measured line shapes and optical modes for samples prepared on ion beam cleaned InSb at Tsub ≤ 100 °C revealed abrupt interfaces while noticing segregated Sb atoms and In2Te3-like precipitates at CdTe-InSb interfaces for films grown on ion beam cleaned InSb at Tsub ≥ 230 °C. Our simulated reflectivity results, using a traditional multilayer (ambient/film/substrate) optics methodology, are compared reasonably well with the experimental data. To substantiate the Berreman effect, we have also investigated the transmission and reflectivity spectra of CdTe/InSb epilayers and (CdTe)m/(ZnTe)n/InSb superlattices at oblique incidence (θI = 45°). A clear distinction of the transverse optical (ωTO) phonons in the s-polarization and ωTO and longitudinal optical (ωLO) modes in the p-polarization has established a valuable method of assessing long wavelength optical phonon frequencies in technologically important materials. Comprehensive analysis of HR-XAS results on the structural characteristics of CdTe/InSb epilayers has provided values of bond lengths and coordination numbers in very good agreement with the existing bulk CdTe data.

The reduction in the crystalline quality anisotropy and the in-plane strain for the non-polar a -plane GaN epi-layer with nano-scale island-like SiN x interlayer was studied extensively with scanning electron microscopy, high-resolution X-ray diffraction measurement, and Raman spectroscopy. It was demonstrated that the SiN x interlayer was powerful to suppress the crystalline quality anisotropy in the a -plane GaN epi-layer since the full width at half maximum values of the X-ray rocking curves for both c -direction and m -direction were reduced from 1108 to 780 arcsec and from 2077 to 806 arcsec, respectively. The Raman measurement results also reveal that the SiN x interlayer plays a crucial role in compensating the in-plane strains. In fact, the in-plane compressive strain along m -direction and the tensile strain along c -direction were found to be decreased by approximately 62% and 78%, respectively due to the insertion of the SiN x interlayer.

A series of 3C–SiC films were grown on 4H–SiC substrates with different growth conditions using high-temperature chemical vapor deposition (HT-CVD). The influences of growth temperature (Tg) on the morphology, optical and material properties of films were assessed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman scattering spectroscopy (RSS). Significant effects of Tg on the film crystalline quality were observed from analyzing XRD and RSS results. XPS characterized the surface states of Si, C, O elements, and variations with Tg. The 3C–SiC Raman TO mode was found to shift to lower frequency with the increase of Tg in 1530–1580 °C. Temperature dependent Raman studies indicated the anharmonic coupling and variation of phonon lifetimes. The optimized Tg is obtained.

A comprehensive experimental and theoretical study is presented to empathize the dynamical properties of Bridgman grown Cd1-xZnxTe samples. Low temperature Raman scattering study has offered an excellent testimony to the lattice phonons of the perfect alloys with a strong evidence of Te anti-site defect (TeCd) modes. An average transfer matrix (ATM) Green’s function (GF) method is employed to examine the isotopic shifts of localized vibrational modes (LVMs) of isolated oxygen OTe defects in CdTe and the low frequency A1 and E phonon modes of TeCd. For the nearest-neighbor (NN) OTe – VCd pair, while the ATM-GF’s study revealed quite different values of LVMs from the existing infrared (IR) absorption data – the results, however, provided good justification to a simple perturbation relationship of 16OTe isotopic mode. An excellent agreement between theory and IR data of impurity modes has validated the formation of NN donor–acceptor pairs and next-nearest-neighbor complex centers involving intrinsic defects. The study is important not only for empathizing the growth process of technologically important Cd1-xZnxTe alloys but also identifying the role of carrier compensation mechanism by various donors and acceptors.

This paper investigates the systematic influence of thickness (136–412 nm) and temperature (300–860 K) on the refractive index and the band-edge of aluminum nitride (AlN) films. The combination of x-ray diffraction, spectroscopic ellipsometry (SE), and transmittance measurements at 300 K shows that the increase of epilayer thickness or the introduction of an AlN interlayer can improve the crystal quality. This is observed as an enlargement of the grain size, a reduction of the Urbach binding energy, and strain with a corresponding increase in the refractive index and bandgap. Moreover, the expected reduction in the bandgap and the increase of the refractive index are observed at elevated temperatures by SE. The temperature dependence of the refractive index at 632.8 nm and the bandgap were well understood and modeled using a quadratic nonlinear equation and the Bose–Einstein equation, respectively. This high-temperature phenomenological and quantitative analysis suggests that the reduction of the bandgap with temperature is more significant in thinner or noninterlayer films than expected due to the corresponding stronger electron–phonon interactions involved with larger Urbach binding energies. The thickest AlN film in this work (with an epilayer thickness of 412.9 nm and an interlayer thickness of 20.69 nm) has the smallest strength of the average electron–phonon coupling (407 meV) in the temperature range 300–860 K. On the other hand, the temperature-dependent variation of the refractive index in the transparent region is more rapid as the film thickness decreases owing to the high correlation between temperature-dependent bandgap and refractive index. These observations are critical when designing AlN-based device structures that can operate well above room temperature.

A series of AlxGa1-xN/AlN/Sapphire films with x = 0.35–0.75 and different thickness of epi-layer were prepared by metalorganic chemical vapor deposition (MOCVD). Spectroscopic ellipsometry (SE) was used to study the temperature-dependent refractive indices and optical bandgaps of the AlxGa1-xN films ranging from 300 to 823 K. Parametric semiconductor (PSEMI) models were used to describe the dielectric functions of AlGaN/AlN layers. The fitting results of refractive index, energy bandgap, thickness and surface roughness at 300 K are in good agreement with photoluminescence (PL), scanning electron microscopy (SEM) measurements and the existing literature. Our finding indicates that the crystal quality of the samples with x = 0.47 and 0.60 are better than those with x = 0.35 and 0.75. As the temperature rises, the increasing of refractive index for the low Al content AlxGa1-xN layers is stronger than that of high Al content in the transparent region, and the reduction of bandgap with high Al content is larger than that of low Al content. For all the samples (x = 0.35–0.75), an analytical expression for temperature-dependent refractive index in the wavelength range of 195–1650 nm was obtained using the Sellmeier law, and the quantitative analysis of the SE-derived temperature-dependent bandgap was conducted by using the Bose-Einstein equation.

A set of Zn1-xCdxO thin films with different Cd concentrations was deposited on quartz substrates by Pulsed Laser Deposition (PLD). The properties of these films were investigated by variable angle and temperature dependent spectroscopic ellipsometry (SE). The experimental Zn1-xCdxO thin films showed a red shift in the absorption edge with increasing Cd contents at room temperature. For ZnCdO films with the similar Cd concentration, it has been found that the film thickness has important effects on the optical constants (n, k). The variations of optical constants (n, k) and the band gap, E0, with temperature (T) in 25 °C–600 °C for a typical Zn0.95Cd0.05O sample were obtained. The E0 vs T relationship is described by a T- quadratic equation.