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Croissance sélective de pseudo-substrats de GaN sur silicium pour des applications optoélectroniques

Abstract : Light-emitting diodes (LEDs) used in solid lighting systems are made from GaN and its alloys. Although commercial LEDs are mainly developed on sapphire substrate, manufacturers and research laboratories are also interested in silicon substrate, which is cheaper and available in larger diameters. However, its usage raises two issues: the presence of a high dislocation density in epitaxial layers and their tensile stress leading to the formation of cracks. In order to avoid them, solutions exist but require long and complex growth processes resulting in an increase in production costs.The alternative proposed in this thesis is focused on the selective area growth of GaN pseudo-substrates on silicon by metalorganic vapour phase epitaxy (MOVPE). Indeed, selective area growth should make it possible to obtain a good crystalline material displaying a limited stress (avoiding coalescence) while reducing epitaxy duration. Our work focused on the analysis of the influence of growth parameters (growth conditions, mask design, substrate polarity) in order to understand the involved mechanisms and to control the effect of each of them on the material morphology. The growth of hexagonal [000-1] GaN pseudo-substrates on Si (100) was demonstrated by using a textured N-polar AlN layer. Optical and structural characterisations displayed a stress relaxation as well as a good crystalline quality of these structures’ surface material. The growth on top of those of InGaN/GaN multiple quantum wells (MQWs) was then studied for micro-LEDs realisation. However, difficulties have been encountered due to the presence of polarity inversions in pseudo-substrates. These tests also demonstrated the necessity of a complete study of N-polar MQWs growth.
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Submitted on : Monday, November 27, 2017 - 12:27:23 PM
Last modification on : Thursday, June 11, 2020 - 5:04:06 PM

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Gautier Laval. Croissance sélective de pseudo-substrats de GaN sur silicium pour des applications optoélectroniques. Micro et nanotechnologies/Microélectronique. Université Grenoble Alpes, 2017. Français. ⟨NNT : 2017GREAT018⟩. ⟨tel-01649195⟩

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