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GaN and its alloys with InN and AlN are of technological importance for a variety of optical, electronic, and optoelectronic devices due to its high thermal conductivity, wide band gap, high breakdown voltage and high saturation velocity. GaN-based devices now provide superior performance for a variety of high power, high frequency, high temperature, and optical applications. The major roadblock for the full realization of Nitride semiconductor potential is still the availability of affordable large-area and high-quality native substrates with controlled electrical properties. Despite the impressive accomplishments recently achieved by techniques such as hydride vapor phase epitaxy and ammonothermal for GaN growth, much more must be attained before establishing a fully satisfactory bulk growth method for this material. Recent results suggest that ammonothermal GaN wafers can be successfully used as seeds to grow thick freestanding GaN wafers by hydride vapor phase epitaxy. A brief review of defect-sensitive optical and paramagnetic spectroscopy techniques employed to evaluate structural, optical, and electronic properties of the state-of-the-art bulk and thick-film (quasi-bulk) Nitride substrates and homoepitaxial films is presented. Defects control the performance of devices and feeding back knowledge of defects to growth efforts is key to advancing technology.

OBJETIVO: Realizar uma avaliação do efeito da adenotonsilectomia na saturação de oxigênio medida por oximetria de pulso noturna em crianças com distúrbios respiratórios do sono. MÉTODOS: Foi realizado um estudo tipo antes e após a intervenção cirúrgica, utilizando a oximetria de pulso noturna como método de avaliação. Foram avaliadas 31 crianças com suspeita de distúrbios respiratórios do sono e indicação clínica de adenotonsilectomia. RESULTADOS: Vinte e sete crianças completaram o estudo. A idade média foi de 5,2 ± 1,8 anos. Dezoito eram do sexo masculino (66,7%). Vinte e três (85,2%) crianças apresentavam, no exame físico, hiperplasia das tonsilas palatinas graus 3 e 4. Houve melhora significativa no índice de dessaturação de oxigênio (IDO) pós-operatório quando comparado com o pré-operatório (p < 0,001). CONCLUSÃO: A adenotonsilectomia melhorou significativamente a saturação de oxigênio, medida pela oximetria de pulso noturna em crianças com distúrbios respiratórios do sono.OBJECTIVE: To evaluate the effect of adenotonsillectomy on oxygen saturation measured through nocturnal pulse oximetry in children with sleep disordered breathing. METHODS: A pre- and post-intervention study was carried out using nocturnal pulse oximetry. The study involved 31 children who were suspected of having sleep disordered breathing and had been referred for adenotonsillectomy. RESULTS: A total of 27 children completed the study. The mean age was 5.2 ± 1.8 years, and 18 (66.7%) of them were male. Upon physical examination, 23 (85.2%) of the children presented class III or class IV hyperplasia of the palatine tonsils. There was significant improvement in the post-operative period over the pre-operative period in terms of the oxygen desaturation rate (OR = 0.65; 95% CI: 0.5-1.3 vs. OR = 1.63; 95% CI: 1.1-2.4; p < 0.001). CONCLUSION: Adenotonsillectomy significantly improved oxygen saturation, as measured through nocturnal pulse oximetry, in children with sleep disordered breathing.

Detailed spectrometry and optical spectroscopy studies carried out on GaN crystals grown in solution detect and identify Mg as the dominant shallow acceptor. Selective etching of crystals with higher Mg levels than that of the donor concentration background indicates that Mg acceptors incorporate preferentially in the N-polar face. Electrical transport measurements verified an efficient incorporation and activation of the Mg acceptors. These results suggest that this growth method has the potential to produce p-type doped epitaxial layers or p-type substrates characterized by high hole concentration and low defect density. [ABSTRACT FROM AUTHOR]

Single-crystalline InN nanorods were successfully grown on c-Al2O3, GaN, Si(111), and Si(100) substrates by non-catalytic, template-free hydride metal-organic vapour phase epitaxy (H-MOVPE). It was evaluated thermodynamically and confirmed experimentally that the domain of nanorod growth lies in the vicinity of the growth-etch transition. Stable gas phase oligomer formation is suggested as the nucleation mechanism for InN nanoparticle generation. Dislocation-free, high-quality InN nanorods with [00.1] growth axis were formed via an apparent solid-vapour growth mechanism. The nanorod diameter, density, and orientation were controlled by growth temperature, substrate selection, and HCl/TMIn and N/In inlet molar ratios. [ABSTRACT FROM AUTHOR]