Defect and Diffusion Forum Vol. 425

Abstract: InSb-based self-assembled quantum dots (SAQDs) are very promising for the mid-infrared (3-5 μm) optical range. We have analysed the electronic structure and optical properties of InAs_xSb_1-x/InAs dots. In this paper, we present the results of the modelling of electronic structure and optical properties from photoluminescence (PL) measurement for InAs_xSb_1-x/InAs SAQDs, focusing on the effects of SAQD morphology and composition. In particular, we analyse the electronic structure of InAs_xSb_1-x/InAs SAQD of various shapes, aspect ratios and compositions. We also suggest a method of assessing the geometry and composition of InAs_xSb_1-x/InAs quantum dots using their optical spectra and limited microscopy information. The calculated transition energies agree well with the experimental results. The results show that the geometry of the dot can be estimated from the optical spectra if the composition is known, and vice versa.

Abstract: Indium gallium nitride / gallium nitride (InGaN/GaN) heterostructures were grown by using metal organic vapor deposition technique with four different growth temperatures (740 °C, 760 °C, 780 °C, and 800 °C). The structural properties and crystalline quality were investigated using high resolution X-ray diffraction (HRXRD) technique. XRD ω-2θ scan mode at GaN (002) diffraction plane was performed to assess the film’s quality. Through the simulation fitting, the indium composition and the thickness of the thin films were obtained. From the observation, an increase in the growth temperature resulted in higher intensity and smaller full-width at half maximum value of the InGaN (002) diffraction peak, which indicated improvement to the crystalline quality of the InGaN/GaN heterostructure. Moreover, the indium composition of the InGaN epilayer was found to decrease with an increase of the growth temperature due to the thermal decomposition of In-N bond and its re-evaporation from the growing surfaces.

Abstract: The structural, electronic and optical properties of lithium niobate (LiNbO₃) and manganese (Mn)-doped LiNbO₃ are investigated using a first-principles study. The first-principles calculation in this work is implemented using CASTEP computer code with GGA-PBE correlation. The band structure and density of states are calculated to analyze the effect of Mn doping on the electronic properties of LiNbO₃. Hubbard U correction is applied to Nb 4d state with U= 11 eV and the corrected band gap obtained is 3.771 eV. LiNbO₃ doped with Mn shows a reduction in the band gap energy which is 1.9889 eV. The dielectric constant and refractive index of LiNbO₃ and Mn-doped LiNbO₃ are also calculated. The optical absorption results suggest there is a shift in the absorption edge towards the visible region in comparison with the LiNbO₃. The improvement in band gap and optical absorption in Mn-doped LiNbO₃ making it a promising material for photovoltaic and photocatalysis applications.

Abstract: Nanocrystalline SnO₂-Y₂O₃ thin film has been successfully prepared by using chemical bath deposition method at low reaction temperature 72 °C on SiO₂/Si substrates. The structural and surface morphology of the annealed sample at 500 °C for 2 h in air were investigated using X-ray diffraction, field emission scanning electron microscopy and Energy-dispersive X-ray spectroscopy. The crystallization of SnO₂-Y₂O₃ film with tetragonal rutile structure was achieved when the film was exposed to annealing at 500 °C. Where several diffraction peaks that correspond to the (110), (101), (200), (211), (220) and (002) planes that agree very well with standard bulk SnO₂ having a tetragonal rutile structure. As well as the diffraction peak that correspond to (111) emerged at θ = 29.48^o is matched with bulk Y₂O₃. The surface morphology appeared as polycrystalline with uniform nanoparticle distribution. The EDX spectra of examined film showed the film consists of O, Sn, Y, and Si elements. The cross-section image and the average thickness of the annealed SnO₂-Y₂O₃ film at 500 °C was approximately 330 nm. Additionally, approximately 880 nm thick layer of SiO₂ emerges on the top of the silicon substrate. This finding demonstrates the ability to prepare nonocrystalline SnO₂-Y₂O₃ thin film with high quality by using chemical bath deposition method.

Abstract: Indium doped zinc oxide (IZO) thin films were fabricated on glass substrates by spin coating technique for transparent conducting oxide (TCO) application. Effect of different indium concentration on their properties were investigated. IZO thin films were deposited on glass substrate using sol-gel spin coating techniques using zinc acetate dihydrate, indium nitrate hydrate, absolute ethanol, and monoethanolamine (MEA). The concentration of indium was varied at 1, 3, 4, and 5 at.%. to study the characteristics of the IZO thin films in terms of structural, optical, and electrical, which is to achieve high visibility of IZO as transparent conducting oxide. The UV-Vis examination of IZO thin film observed that the highest transparency of thin films was IZO with indium concentration of 4% which shows a75.6%. The optical band gap were calculated using Tauc’s plot and was found to be in the range between 3.10 to 3.2 eV. For electrical properties, the lowest resistivity was observed for IZO thin film at 4% doping concentration with a value of 3.25 Ωcm, while the highest resistivity was observed at IZO thin film at 1% which is 15.26 Ωcm.

Abstract: Point defects in silicon carbide (SiC) are well positioned for integration with SiC based quantum photonic devices due to the maturity of SiC material and fabrication technology, the plethora of candidate quantum emitters that can be formed in SiC, and the potential for emission over a wide spectral range from the visible to the infrared. However, for each of the available color centers in SiC, only one of the charge states has displayed quantum emission, meaning that the emission strongly depends on the Fermi level and hence the doping concentration in the material. In this contribution, we discuss the methodology and mechanism for electrical charge-state control over point defects in SiC devices.

Abstract: A highly efficient, high-voltage power switching technology, the Optical Transconductance Varistor (OTV) is being developed based on the photoconductive property of 6H-SiC. The behavior of the dislocations in 6H-SiC under the application of voltage and laser in such devices is of particular interest. In this study, both ex-situ and in-situ synchrotron X-ray topography were applied to characterize dislocations and investigate their behaviors when the sample was electrically and photonically stressed. Threading dislocations (TDs) and basal plane dislocations (BPDs) were revealed in transmission topographs and grazing topographs. When the samples were connected to external voltage ranging from 1kV to 4kV, there were no observable signs of dislocation movement. This indicates that the energy released from the transitioning of Vanadium states is lower than the activation energy for dislocation gliding.

Abstract: Correlation of X-ray topography and production line defect inspection tools has demonstrated the capability of in-line tools to differentiate between geometrically comparable basal plane slip bands (BPSB) and bar stacking faults (BSF) on 4H SiC wafers. BPSBs were found to propagate through epitaxial growth at high rates and with similar photoluminescence signatures to post-epitaxy BSFs. Molten KOH etching post-epitaxy provided evidence of distinguishing features between BPSBs and BSFs, suggesting that the defects were indeed correctly identified by in-line defect inspection tools pre-epitaxy.

Abstract: SmartSiC^TM technology enables the supply of cost-effective and high-quality substrates to support the manufacturing of Silicon Carbide (SiC) Power Devices and the transition to High Volume Manufacturing (HVM) [1]. As detailed in [2] SmartSiC^TM is prepared using a poly-crystalline handle wafer, it combines the benefit from both an optimized high quality epi-ready 4H-SiC layer and an ultra high conductivity handle material. Smart Cut^TM technology can be extended to SiC 200mm substrates and first SmartSiC^TM 200mm sample has been prepared [2].SmartSiC^TM substrates crystal quality is inherited by donor wafers [1, 2] and do not require a systematic control, enabling a new defects monitoring strategy, focusing on surface defects.This paper describes how a commercially available DUV inspection system was utilized for high sensitivity, high-throughput inspections of 150 and 200 mm 4H-SiC and SmartSiC^TM substrates, for the HVM environment. The KLA Surfscan^® SP A2 unpatterned wafer inspection system offers the opportunity to complement other inspection technologies to optimize SiC substrate defect control, with low threshold detection, below 150 nm.