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Scanning thermoelectric and acoustic emission diagnostic of structural inhomogeneities of thermocouple materials

Prokhorenko V. J., Prokhorenko S. V., Mudry S. I., Sheregii E. M., Dominjuk T. I.

Archives of Foundry Engineering

2010

Vol. 10, iss. 1 spec.

381--386

New method for diagnostic of constructional and functional materials by means of thermoelectric and acoustic- emission measurements is proposed. The method allows not only to establish the defect location, but its partial temperature relaxation achieve.

Defect structures in InGaN/GaN multiple quantum wells on Si(111) substrates

Wu G. M., Kao Y. L.

Journal of Achievements in Materials and Manufacturing Engineering

2006

Vol. 18, nr 1-2

195--198

Purpose: Nitrides are compound semiconductor nanomaterials that are suitable for use in light-emitting diodes. It has been desired to grow high quality gallium nitride crystal thin film on silicon substrates because silicon substrates have the advantages of low cost, large wafer size, and good electrical and thermal conductivity. However, the higher defect density can limit the industrial applications due to lower quantum efficiency. The purpose of this study has been to investigate the crystal defect structure within InGaN/GaN multiple quantum wells on Si(111) substrates. In addition, the variation in quantum well thickness was also explained by the selective area growth model. Design/methodology/approach: InGaN/GaN nano-structures were prepared by metal-organic chemical vapor phase epitaxy (MOVPE) using composite buffer layers. The crystal defect structures in the buried multiple quantum wells on both (0001) and {10-11} sidewalls were carefully studied by transmission electron microscopy. Previous studies on sapphire substrates have been compared and discussed. Findings: The V defect structures have been found in InGaN/GaN multiple quantum wells on Si(111) substrates. A simplified structural model with increasing barrier thickness has been reported. The barrier thickness increased on both (0001) and {10-11} facets along thin film growth. A decreased fill factor based on the selective area growth model was proposed. In addition, the average thin film growth rate was found to be four times higher along (0001) than that along {10-11} facet. As the number of multiple quantum wells increased, the barier thickness increasing was also intensified. Research limitations/implications: The understanding in defect structure could help to modify the processing and design parameters. Originality/value: The V-defect structure and model were reported for the first time using silicon substrates. The different growth rates along defect structures were quantified. High quality gallium nitride crystal could be manufactured along with better substrate design.