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oai:figshare.com:article/32640234 2026-10-01T16:33:02Z portal_1172 item_type_8 month_year_10_2026

TEM studies of III-V metamorphic buffer architectures for laser applications Nicholas James Stephen (24169137) PUREID: 614326519 Transmission Electron Microscopy bandgap energy dislocations strain metamorphic growth This study explores different In_xGa_1-xAs metamorphic buffer (MB) architectures grown on GaAs and InP substrates via Metal Organic Vapour Phase Epitaxy (MOVPE), focusing on physical factors that affect laser performance. The research examines chemical composition, strain, and dislocation distribution in MBs, with localized bandgap (Eg) measurements in In_xGa_1-xAs Quantum Wells (QWs) using transmission electron microscopy (TEM).<br><br>Strain mapping in MBs on GaAs substrates with various designs, including In_0.66Ga_0.34P films and Al_xIn_yGa_1-x-yAs/In_xGa_1-xP superlattices, shows dislocation densities between 10⁸ cm⁻² and 10¹⁰ cm⁻². Samples with superlattices have higher dislocation densities despite similar MB designs, likely due to growth process differences. Threading dislocations (TDs) are found deeper in the MB (~200–300 nm) than misfit dislocations (MDs). Strain mapping aligns with theoretical models, indicating higher strain in the growth direction (εyy) than in-plane (εxx).<br><br>InP substrates show higher dislocation densities and a smaller distance between TDs and MDs compared to GaAs samples. These findings provide insight into strain relaxation strategies for metamorphic lasers.<br><br>Electron energy loss spectroscopy (EELS) reveals bandgap variations in QWs, while energy dispersive X-ray (EDX) and strain mapping highlight the interplay between strain, composition, and Eg. This offers fundamental insights for improving the electronic and optical properties of metamorphic laser structures on different substrates.<br> 2026-10-01T16:33:02Z Text Thesis 10.17034/32640234.v1 https://figshare.com/articles/thesis/TEM_studies_of_III-V_metamorphic_buffer_architectures_for_laser_applications/32640234 All Rights Reserved