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Title: Gallium nitride light-emitting diode enabled visible light communications
Author: Ferreira, Ricardo Xavier da Graça
ISNI:       0000 0004 6499 6062
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2017
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This thesis focuses on the development, measurement and application of novel micrometre-sized light emitting diodes (micro-LEDs) based on Gallium Nitride (GaN) for visible light communications (VLC) in both free-space and guided wave configurations. The goal is to set benchmarks for LED-based wireless optical communications. An overview of the field integrating research, industry and standards is presented. A top-down approach is taken with application requirements driving development of new micro-LEDs with simultaneously increased optical power and modulation bandwidth. This was achieved by mitigating two limitations, namely current crowding and mutual device heating. Two novel techniques were developed to access pixel performance: spatially-resolved mapping of modulation bandwidth and spectral characteristics, and thermal imaging. On this basis, broad-area LEDs were used to understand the independent benefits, providing insight for the design of novel micro-LEDs. Circular segmented micro-LEDs emitting at 450nm achieved modulation bandwidths in excess of 800MHz, the highest reported for LEDs, while maintaining optical power above 2mW. In data transmission using systems with 1.8GHz bandwidth,the devices achieved 8Gbps in free-space and guided-wave operation at wavelengths of 400nm, 450nm and 520nm. Ring and half-ring micro-LEDs introduced here have shown modulation bandwidths that scale with the increase of active area and consequently optical power. Bandwidths in excess of of 600MHz were achieved at optical powers over 5mW. In data transmission using a system limited to 1GHz bandwidth, these devices achieved 7Gbps in free-space operation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral