We will present recent findings on the physics of III-nitride recombinations, including the demonstration of defect-assisted Auger recombination as a significant droop process, and the intricacies of low-current radiative recombinations, where alloy disorder and Coulomb interaction play a key role. We will discuss implications for future LED applications, from long-wavelength devices to low-power micro-LEDs.
We study photonic crystal (PhC)-assisted light extraction from gallium nitride (GaN) light-emitting diodes (LEDs). We focus on the issue of omnidirectional extraction, and we introduce a complex crystal lattice, namely the Archimedean tiling, which enables efficient and omnidirectional light extraction. PhC LEDs with regular triangular lattices and Archimedean lattices are studied experimentally by angle-resolved luminescence, and the theoretical properties of the Archimedean tiling are confirmed experimentally.
We are progressively approaching the physical limits of microcavity LEDs (MC-LEDs) for high brightness, high efficiency LEDs. They are promising high efficiency devices and they offer the very attractive prospect of full planar fabrication process. However, to compete with other high efficiency LED schemes, they need to approach or surpass the 50 % efficiency mark. We first explore the limits of planar MC-LEDs in both the GaAlInAsP and GaInAlN materials systems, and show that the single-step extraction limit is in the 40 % range at best, depending on the materials system used, with the largest part of the non-extracted light being emitted into guided modes. The waveguided light can itself be extracted by photon recycling, when the internal quantum efficiency is high. Otherwise, another extraction scheme for that light is provided by various photonic-crystal-assisted extraction schemes. Simple photonic crystals (PCs) appear to lack the omnidirectional extraction properties required. However, more rotation-invariant PCs like Archimedean tilings allow to obtain such extraction with added efficiencies already in the 10% range. We discuss the further improvements to such structures.
Conference Committee Involvement (5)
Light-Emitting Devices, Materials, and Applications XXV
6 March 2021 | Online Only, California, United States
Light-Emitting Devices, Materials, and Applications XXIV
3 February 2020 | San Francisco, California, United States
Light-Emitting Devices, Materials, and Applications
4 February 2019 | San Francisco, California, United States
Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XXII
29 January 2018 | San Francisco, California, United States
Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XXI
30 January 2017 | San Francisco, California, United States