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Title: Novel micro-pixelated III-nitride light emitting diodes : fabrication, efficiency studies and applications
Author: Tian, Pengfei
ISNI:       0000 0004 5362 8539
Awarding Body: University of Strathclyde
Current Institution: University of Strathclyde
Date of Award: 2014
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This thesis presents a systematic study of the fabrication, efficiency and applications of micro-pixelated III-nitride light emitting diodes (micro-LEDs). Efficiency droop studies of micro-LEDs and the development of new-types of micro-LEDs have been investigated. The size dependence and temperature dependence of micro-LED efficiency droop have been analysed, providing a deep understanding of efficiency droop issue for general lighting and also demonstrating the advantages of micro-LEDs to alleviate such efficiency droop. Micro-LEDs on flexible substrates have been fabricated, which combine the flexibility of soft substrates and the high efficiency of inorganic LEDs for potential applications in flexible displays, biomedicine, etc. In addition, micro-LEDs on Si substrates were also fabricated to reduce the micro-LED device fabrication cost. The size-dependent efficiency droop study demonstrates that the smaller micro-LEDs have more uniform current spreading, which causes their higher efficiency and higher thermal saturation current density. In addition, the temperature-dependent efficiency droop study shows that both the radiative and Auger recombination coefficients decrease with increasing temperature, and the temperature dependence of the radiative and Auger recombination coefficients is weaker at a higher current density. So micro-LEDs possess stabler temperature dependent efficiency when operating at a high current density. Flexible micro-LEDs have been fabricated using metal bonding and laser lift off techniques with only one transfer step. Also, the micro-LED arrays on Si substrates were developed for the first time, which have lower fabrication cost compared with micro-LEDs on sapphire substrates. The applications in micro-display and visible light communication have been demonstrated for both the devices above. This work suggests that employing micro-LED techniques is a way to improve LED efficiency for general lighting. With development of flexible micro-LEDs and reduced fabrication cost of micro-LEDs on Si substrates, the future applications of micro-LEDs are expected to be greatly expanded.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available