Embedded photonic crystals for high-efficiency gallium nitride-based optoelectronic devices

The application of photonic crystals (PhCs) as light extractors in LEDs has evoked increased interest over recent years due to their efficacy in controlling the direction of light emission and enhancing the extraction efficiency of LEDs. This dissertation presents the study of different schemes for higher light extraction based on PhCs. The higher theoretical light extraction provided by structures with embedded PhCs compared to all the other configurations motivated a more detailed investigation of this approach.The growth of embedded air-gap PhCs by MOCVD was successfully achieved with very short grating periods (230 nm) in a two-dimensional triangular lattice. Coalescence was obtained over the air-gap PhCs with thicknesses down to 50 nmand fairly smooth surface with no extra defects created by the embedded PhCs. Embedded PhC structures were optimized using full 3D electromagnetic models. The embedded PhC LEDs presented a very high extraction efficiency of 73% for unencapsulated and 94% for silicone encapsulated devices.In addition, we developed new techniques to measure intrinsic characteristics of PhC LEDs based on high resolution angle-resolved measurements. The measurement of the extraction and dissipation properties of guided modes in PhC-LEDs revealed the competition between these two mechanisms as well as the dynamical diffraction by the 2D PhCs. These experimental techniques were used to corroborate some of our theoretical results and to compare the performances of different PhC configurations.The diffraction of the guided modes with short extraction lengths, shorter than any absorption mechanism, explains the very high extraction efficiency of the embedded PhC LEDs presented in this PhD thesis, which makes this structure an excellent candidate for high efficiency and high brightness LEDs.