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Title High performance microstructured light emitting diodes : mechanisms and processes / by Enyuan Xie.
Name Xie, Enyuan .
Abstract At high current densities, the µ-LEDs with optimized Pd-based contacts have better electrical performance compared with devices using oxidized Ni/Au contacts. The optimized Pd-based contact also leads to improved optical power for blue LEDs in flip-chip configurations. III-nitride microstructured-image LEDs are devices in which micro-scale emission patterns are created in single LEDs. These devices offer a simple approach to the display of high-resolution images. CHF3 plasma treatment is a novel technique used for the fabrication of these devices. This plasma treatment can locally modify the electrical properties of p-type GaN and define the emission image. An application of these devices for maskless image writing is demonstrated.
Abstract The research work presented in this thesis focuses on the mechanisms and development of novel III-nitride microstructured light emitting diodes (LEDs). In particular, we focus on micro-sized LEDs (`µ-LEDs') and LEDs containing micro-scale emission images i.e. `microstructured-image LEDs'. III-nitride µ-LEDs, which are devices with dimensions less than 100µm, show improved device performance and novel potential applications compared with broad- area LEDs. The internal electric field in III-nitride materials, which is mainly caused by the strain due to lattice mismatch with the substrate, is a serious issue for III-nitride LEDs. As the strain can be relaxed in micro-scale structures, the performance of µ-LEDs can be improved. In this work, we have investigated the strain relaxation process in III-nitride micro-pillars as a function of pillar diameter by high-spatial-resolution cathodoluminescence. The results of this study give a guideline for furthe r design of µ-LEDs with high efficiency. The internal electric field can also be screened by injection of carriers, leading to a blue-shift of the emission wavelength for III-nitride LEDs. Due to the high operating current density that µ-LEDs can sustain, the magnitude of this blue-shift is remarkably increased for µ-LEDs. Based on this characteristic, colour-tunable µ-LEDs have been demonstrated in this work, which offers a simple way to achieve multi-colour displays. In order to further improve the performance of µ-LEDs, we have also developed Pd-based contacts to p-type GaN and investigated the current-density dependent specific contact resistivity.
Publication date 2013
Name University of Strathclyde. Dept. of Physics.
Thesis note Thesis PhD University of Strathclyde 2013 T13420
System Number 000002332

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